Class 8 Chemistry - Materials Metals And Non Metals

(i) Write the chemical equation for the reaction between gallium(III) oxide and dilute nitric acid to form a salt and water only.

(ii) The reaction between gallium(III) oxide and sodium hydroxide solution forms only water and a salt containing the negative ion $$Ga_2O_4^{2-}$$ Write the chemical equation for this reaction.

$$\textbf{(i)}$$

The chemical equation for the reaction between gallium(III) oxide and dilute nitric acid to form a salt and water only is:-

$$Ga_2O_3 + 6HNO_3 \rightarrow 2Ga(NO_3)_3 + 3H_2O$$

$$\bullet$$ Gallium oxide react with nitric acid to produce nitrate gallium (III), and water.

$$\textbf{(ii)}$$

The reaction between gallium(III) oxide and sodium hydroxide solution forms only water and a salt containing the negative ion $$Ga_2O_4^{2-}$$ is:-

$$Ga_2O_3 + NaOH \rightarrow Na_2Ga_2O_4 + H_2O$$

Give a reaction to show that metals react with base.

$$\bullet$$ When alkali (base) reacts with a metal, it produces salt and hydrogen gas.

Example:

Sodium hydroxide$$(NaOH)$$ gives hydrogen gas$$(H_2)$$ and sodium zincate $$(Na_2ZnO_2)$$ when reacts with zinc$$(Zn)$$ metal.

The reaction occurs as :

$$Zn + 2NaOH \xrightarrow [] {Heat} Na_2ZnO_{2(aq)} + H_{2(g)}$$

Why metallic oxides are called basic oxides and non-metallic oxides are called acidic oxides?

$$\textbf{Part 1: Metallic oxides are called basic oxides}$$

Metallic oxides are called basic oxides because,

$$\bullet$$ They react with dilute acids to produce salt and water.

For example, $$MgO+2HCl\rightarrow MgCl_{2}+H_{2}O$$

$$\bullet$$ When metallic oxides are dissolved in water, they produce metallic hydroxides which are alkaline in nature.

For example,

$$MgO+H_{2}O\rightarrow Mg\left(OH\right)_{2}$$

$$\textbf{Part 2: Non-metallic oxides are called acidic oxides}$$

Non-metallic oxides are called acidic oxides because,

$$\bullet$$ When non-metallic oxides are dissolved in water, they produce acids.

For example, The chemical equation for the reaction of carbon dioxide with water is as follows:

$$CO_{2}+H_{2}O\rightarrow H_{2}CO_{3}$$ (Carbonic acid)

Match the substances in Column A with their applications given in Column B.

Oxygen is compulsory for breathing and all living beings inhale it during the same.

Copper is a good conductor of electricity, so, used for making electric wires.

Crackers use large quantities of sulphur and paper.

Iron is used to make steel and steel is used for making railway lines.

Chlorine is one of the most commonly used disinfectants for water disinfection.

Chlorine can be applied for the deactivation of most microorganisms.

Which is lustrous?

Iodine is a non metal which is lustrous.

Which is a liquid at room temperature?

Bromine is a non metal which is a liquid at room temperature.

Malleability is the ability of a metal to be beaten into thin sheets. Explain.

Malleability is the ability of a metal to be hammered into thin sheets. Metals can be flattened by hammering or rolling. Gold and silver are examples of highly malleable metals. This property is not seen in non-metals.

How can two objects that are the same temperature are felt by you as if they are at different temperatures ?

Two objects that are at the same temperature can feel as though they are at different temperatures if one object is a better conductor of heat than the other is. The better conductor will feel colder because it will draw heat energy from your hand faster.

Name the non-metal used to make an antiseptic solution called tincture?

Iodine is the non-metal used to make an antiseptic solution called tincture. The plant extract dissolved in ethanol is known as tincture and it has antiseptic properties which prevent the growth of bacteria. Tincture of iodine contains 2-7% of iodine along with sodium or potassium iodide dissolved in ethanol and water. It is applied on cuts and wounds to heal them.

Sodium and potassium are stored under oil. Give reason.

Sodium and potassium are stored under oil because they react with oxygen so vigorously that they catch fire if kept in the open. Hence, to protect them they are kept immersed in kerosene oil.

Prateek took a piece of burning charcoal and collected the gas evolved in a test tube. How will he find the nature of the gas?

Charcoal is a form of carbon that is non-metal. When non-metal reacts with air, it forms a non-metallic oxide which is acidic in nature. Thus, when charcoal burns in the air it forms an acidic oxide called carbon dioxide.

The nature of gas can be found by adding water to the gas in the test tube and then put some blue litmus solution in the test tube. If the blue litmus solution turns red, it means that the gas is acidic in nature.

Give an example of activity to show that metals burn in air to form base.

Clean a magnesium ribbon about $$\text {2 cm}$$ long by rubbing it with sandpaper. Hold it with a pair of tongs. Burn it using a spirit lamp or burner and collect the ash so formed in a watch-glass. Burn the magnesium ribbon keeping it as far as possible from your eyes. When magnesium ($$Mg$$) ribbon is burnt in oxygen($$O_2$$), it gets converted to magnesium oxide ($$MgO$$). To collect this rust of magnesium oxide and dissolve it in a little amount of water. If we shake this mixture and test it with litmus paper then we observe that red litmus turns blue. This is because when we dissolve magnesium oxide ($$MgO$$) in water($$H_2O$$) it forms magnesium hydroxide($$Mg(OH)_2$$). Magnesium hydroxide is basic in nature.

So we can conclude that when metal burns in the air they form a base.

Explain why we don't store lemon pickle in an aluminum utensil.

Lemon pickle cannot be stored in $$Al$$ foil as the pickle is acidic in nature which reacts with $$Al$$ metal liberating hydrogen gas and this can lead to spoiling of the pickle.

Name two non-metals whose oxides are acidic in nature.

$$Carbon$$ and $$Sulphur$$ are non-metals forming Carbon dioxide and Sulfur dioxide which in aqueous solution form Carbonic acid and Sulphurous acid which are acidic in nature.

Complete the following reactions:
$$Zn\, (s)\, +\, NaOH\, (aq)\, \xrightarrow[]{heat}$$

$$\displaystyle Zn\, (s)\, +\, NaOH\, (aq)\, \xrightarrow[]{heat} \underset {\text {Sodium zincate}}{Na_2ZnO_2(aq)} + H_2(g) $$

State four differences between metals and non-metals.

$$\text{Metals:}$$ 1) sonorous in nature

2) good conductor of heat and electricity

3) ductile and malleable

4) lose electron

$$\text{Non-metals:}$$ 1) not sonorous in nature

2) poor conductor of heat and electricity except graphite

3) non-ductile and not malleable

4) gain electron

You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.

When a copper vessel is exposed to moist air for a long time, a dull green colored layer is formed on it. This greenish layer is a mixture of copper hydroxide ($$Cu(OH)_2$$) and copper carbonate ($$CuCO_3$$).

The reaction is

$$2Cu + H_2O + CO_2 + O_2$$ $$\longrightarrow Cu(OH)_2 + CuCO_3$$

As these products are basic in nature, to clean them lemon or tamarind juice-like acidic substances are needed. These sour substances are effective in cleaning the copper vessels hence are considered for cleaning.

Differentiate between metals and non-metals on the basis of their chemical properties.

$$Metals$$	$$Non-metals$$
Metals react with oxygen to form basic oxides. $$4Na + O_2 \rightarrow 2Na_2O$$	Non-metals react with oxygen to form neutral or acidic oxide. $$C + O_2 \rightarrow CO_2$$
Metals react with water to form hydroxide and hydrogen. $$2Na + 2H_2O \rightarrow 2NaOH + H_2$$	Generally, non-metals do not react with water.
Metals react with dilute acids to form salt and $$H_2$$.	Non-metals do not react with dilute acids and they cannot displace hydrogen.

Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).

What type of oxides are formed when non-metals combine with oxygen?

$$Explanation:$$

The non-metals react with oxygen to form covalent compounds, which show acidic nature.

For example, sulphur reacts with oxygen gas to form sulphur dioxide. Sulphur dioxide shows acidic nature. it turns moist blue litmus paper to red.

$$ S + O_2 \rightarrow SO_2 $$
$$ SO_2 + H_2O \rightarrow H_2SO_3$$

Therefore, we can say that acidic oxides are formed when non-metals combine with oxygen.

True or False.
Non-metals have many different colours.

$$\text False.$$

Typical nonmetals have a dull, coloured or colourless appearance. Hence, the given statement is false.

Brain Nurtures
A solution of $$CuSO_4$$ was kept in an iron pot. After a few days, the iron pot was found to have a number of holes in it. How were these holes formed?

Reaction takesplace in the solution.

$$\underset { Copper \ (II) \ sulphate \\ (Blue \ solution)} {CuSO_4(aq)} + \underset {Iron \ metal} {Fe(s)} \longrightarrow \underset{ Iron \ (II)\ sulphate \\ Greenish \ solution} {FeSO_4(aq)} + \underset{ Copper \ metal}{ Cu(s)}$$

The above reaction indicates that there is a reaction between copper sulphate solution and iron metal. Iron metal is more reactive than copper hence it can displace copper from its solution. Due to the reaction of iron metal with copper sulphate solution, some of the iron from the surface of the iron pot moves into the solution. This results in the number of holes in it.

The binary compounds of metallic or non-metallic elements with oxygen are called as __________.

Oxides are binary compounds formed by the reaction of oxygen with other elements. Oxygen is highly reactive in nature. They react with metals and non-metal to form oxides. Depending upon nature and the properties exhibited by compounds, they are classified into:

Acidic oxides
Basic oxides
Amphoteric oxides
Neutral oxides

Why do metals generally appear to be dull? How can their brightness be restored?

Metals generally appear to be dull because of their reaction to the moisture of the air. Their brightness can be restored by rubbing with shining paper.

Solder is used for joining two metal surfaces together. Solder is a mixture of lead and tin. Can two metals be separated by distillation?

Soldering filler materials are available in many different alloys for differing applications. In electronics assembly, the eutectic alloy of 63% tin and 37% lead has been the alloy of choice. The constituent of solder i.e. lead and tin differ in their boiling points, hence can be separated by method of distillation.

Name the following:
The property possessed by metals by which they can be beaten into sheets.

Metals are malleable and ductile. The property possessed by metals to be beaten into sheets is called malleability and the property possessed by metals to be drawn into wires is called ductility.

Why is sodium kept immersed in kerosene oil?

Hint: Sodium may easily give up one of its electrons in order to achieve a stable octet configuration.

Explanation:

Sodium $$\left( Na^+ \right)$$ is a highly reactive metal that becomes energized and ignites when it comes into touch with oxygen $$\left( {{O}_{2}} \right)$$, carbon dioxide $$\left( C{{O}_{2}} \right)$$ or moisture $$\left( {{H}_{2}}O \right)$$ in the atmosphere.

The sodium metal is found to be non-reactive in kerosene oil, which is interesting. As a result, the sodium metal is kept submerged in kerosene oil to eliminate the risk of an unintentional fire and to reduce the risk of serious injuries or damage.

Final answer:

Sodium is kept immersed in kerosene oil because it is highly reactive.

True or False:
Nonmetals are less dense and have low melting and boiling points.

Non-metals tend to have relatively low melting and boiling points. Non-metals have intermolecular bonds that are weaker than metallic bonds between metal atoms. Therefore, less energy is needed to overcome the intermolecular bonds between non-metal particles.

So, the given statement is true.

The number of elements that show ductility among the following is?

Copper, silver, phosphorus, platinum, iodine, aluminium, carbon

Most metals are ductile, i.e. they can be drawn into thin wires. Here, copper, silver, platinum and aluminium are metals, and so, will show ductility. The rest are non-metals.

Among the following, the number of elements that do not show malleability is:
Zinc, Iron, Sulphur, Copper, Aluminium, Nickel, Chlorine, Iodine

Answer is 3.

Sulphur, chlorine and iodine elements are non-metals. Non-metals do not show the property of malleability.

Out of the following elements, phosphorus, iron, copper, sulphur, silver, iodine, boron, titanium, the number of elements that don't show ductility is:

Non-metals don't show ductility and here the non-metals are phosphorus, sulphur, iodine, boron and the rest, iron, copper, silver, titanium are metals that show ductility.

Write any six chemical properties of metals.

Chemical properties of metals:
(1) They form positive ions.
(2) They form basic oxides and hydroxides.
(3) They react with oxygen present in atmosphere to form oxides and iron corrodes.
(4) They form metallc bonds.
(5) They react with water to produce $$\displaystyle hydrogen$$ gas.
$$\displaystyle 2Na + H_2O \rightarrow 2NaOH + H_2 \uparrow$$
$$\displaystyle Mg+H_2O \rightarrow MgO + H_2 \uparrow$$
$$\displaystyle 3Fe+4H_2O \rightleftharpoons Fe_3O_4 + 4H_2 \uparrow$$

(6) They react with oxygen to form oxides.
$$\displaystyle 4Na+O_2 \rightarrow 2Na_2O $$
$$\displaystyle 2Mg+O_2 \xrightarrow {\Delta} 2MgO$$
$$\displaystyle 2Zn+O_2 \xrightarrow {\Delta} 2ZnO$$

Guess who I am?
i) I am a cheap metal but highly reactive. Therefore, I sacrifice myself to save the objects made of Iron.
ii) I am a solid solution. Dentists use me to fill cavities.

i) Zinc is used to coat Iron to protect it.
ii) Teeth can be filled with amalgam (which consists of mercury mixed with silver, tin, zinc, and copper).

Select lustrous materials out of the following substances.
Gold, Sand, Silver, Rubber

$$\bf{Concept-}$$

Lustrous materials are basically those materials that have a shiny surface.

$$\bf{Explanation-}$$

Lustrous materials are those that have a shine on them. Due to this property metals are widely used for making jewelry. Example: Gold, silver, and most metals are lustrous in nature.

Name a non-metal that has lustre.

$$\bf{Concept-}$$

A metal or a non-metal is said to be lustrous when it has an intrinsic shining/luster. Similarly, a non-lustrous metal or a nonmetal would be the one that does not have such shining or luster.

$$\bf{Explanation-}$$

$$\bullet$$ Iodine is the most electropositive halogen and also the least reactive one, although it is found to form compounds with many other elements. Iodine is non-metal, has a dark-gray texture. It is evident through different discoveries that iodine is a lustrous non-metal.

$$\bullet$$ Diamond has a very bright luster, so much that it has the highest non-metallic luster.

$$\bf{Conclusion-}$$

Both the iodine and diamond which is essentially a non-metal form of carbon are non-metals. Moreover, it could be concluded that both of them are lustrous.

Why aluminum alloys are used to design the body of an aircraft? Give reasons.

Aluminum alloys such as duralumin are light, tough, and resistant to corrosion and hence are used to make aircraft bodies.

Complete the reaction given below:-

$$2Mg+{O}_{2}\rightarrow$$ ?

Magnesium combines with oxygen to form its metal oxide.

$$\Longrightarrow$$ $$2Mg+{ O }_{ 2 }\rightarrow 2MgO$$

Write chemical properties of metal and non-metal.

Chemical properties of metal:

(i) Reactive metals liberate $$H_2$$ gas when treated with strong/weak acid or base.

(ii) Alkali metals show flame coloration.

(iii) Metals like $$Fe, Mg, Ni$$ form organometallic compounds.

Chemical properties of non-metal:

(i) Highly electronegative non-metals like chlorine and oxygen form strong hydrogen bonds.

(ii) Non-metals react with metals to form ionic compounds.

Name two non-metals used in crackers?

Non-metals such as Sulphur and Phosphorous are used to manufacture crackers.

Fill in the blank:
Property of metal by which it can be beaten into sheets is called __________.

Answer: Property of metal by which it can be beaten into sheets is called $$\underline {malleability}$$.

The property which allows metals to be hammered into thin sheets is called malleability. Gold and silver are highly malleable metals.

Which metal used in making bulb's filament is highly ductile?

Tungsten is the metal that is used for making the filaments in the bulb.

Tungsten like all other metals is malleable and quite ductile (can be readily drawn into wires)

Give reason:
Metals forms positive ions.

Metals form positive ions because metals are very electropositive, and their outer electrons are very loosely bunded on them. so, that they lose electrons and gain a positive charge and hence from positive ions.

List any three chemical properties based on which metals and non-metals are differentiated.

Hint: Metals are ductile, lustrous, and malleable while non-metals are not.

Explanation:

Metals and non-metals are differentiated by the following chemical properties:

Metals	Non-metals
The oxides of metal are basic in nature.	The oxides of non-metals are acidic in nature.
Metals form ionic compounds with halogens.	Non-metals form covalent compounds with halogens.
Hydrogen is displaced by metals in water.	There is no displacement of hydrogen by non-metals in water.
Metals are electropositive.	Non-metals are electronegative.
They lose electrons to form positive ions.	They accept electrons to form negative ions.

Why are metals used for making cooking vessels?

Generally, cooking vessels are made from metals because they conduct heat well, and are chemically unreactive, so that they do not alter the flavor of the food. Metals transfer heat by conduction pretty quickly and evenly and are generally tolerant to rapid changes in temperature.

Which non-metal has very high melting and boiling points?

Diamond and Graphite has more melting and boiling points. Because they are the substances with giant covalent structures have very high melting points, because a lot of strong covalent bonds must be broken.

Explain the reactions of metals with air (oxygen)?

1352722_1287710_ans_fc7aa6389606438bb1fd1f14da113c07.jpeg

Define malleability.

The property of a metal due to which it can be beaten into sheets is known as malleability. It varies according to the temperature. Metals are malleable in nature. For example, silver, gold, copper, iron, etc exhibit the property of malleability.

Differentiate between metal and non-metal on the basis of their chemical properties.

1414578_1471174_ans_9a9c2451903441d1960d0b16f42e16d0.jpg

Name the most malleable metal in the world.

Malleability refers to the physical property of a metal to be pressed, hammered and rolled into thin sheets without breaking. Gold, chemical element with Latin name $$Aurum$$ and symbol $$Au$$ is the most malleable metal in the world.

Metals are _and plastic are of heat.

Metals are $$\text{good conductor}$$ and plastic are $$\text{bad conductor}$$ of heat.

What is malleability?

Malleability is a property of a material by which it can be beaten to form thin sheets. Most metals are malleable. Examples of malleable metals are zinc, iron, aluminum, copper, gold, and silver.

Why silver turns into black after a long time? Give the reason.

Silver articles become black on exposure to air for sometime. When silver articles exposed to air silver reacts with sulphur present in the atmosphere and form a black layer of silver sulphide on the surface.

Give three differences between metals and non-metals.

Basis for comparison	Metals	Non-metals
Malleability	Are malleable	Are non-malleable
Ductility	Are ductile	Are not ductile
Reaction with acids	Generally, react with acids to produce hydrogen gas	Generally, do not react with acids

Why each metal can not react to its own salt (e.g. $$Cu$$ and $$CuSO_{4}$$)?

Each metal cannot react to its own salt because the reactive strength of the metal will be the same in both examples $$Cu$$ and $$CuS{O}_{4}$$. In both, the metal Cu (Copper) has the same reactive strength.

$$Cu + CuSO_4 \longrightarrow \text {No reaction}$$

If in case there was Fe (Iron which is more reactive than Cu) to be reacted with $$Cu{S}{O}_{4}$$ then displacement reaction would have taken place.

What name is given to those metal oxides which show basic as well as acidic behaviour?

Name given to those metal oxides which show basic as well as acidic behaviour is Amphoteric oxides. Example: $$ZnO,\ Al_2O_3,$$ etc.

Give the names of:
(a) two acidic oxides, and
(b) two basic oxides.

(a) Carbon dioxide and sulfur dioxide are two acidic oxides.

(b) Sodium oxide and magnesium oxide are two basic oxides.

Name one metal and one non-metal which exist in a liquid state at room temperature.

Mercury is a liquid metal and bromine is a liquid non-metal that exist as liquid at room temperature.

Name the metal which is a very bad conductor of heat.

The metal which is a very bad conductor of heat is Lead (Pb).

$$(X_i)$$ $$(Y_i)$$ $$(Z_i)$$
Constantan $$Cu, Al$$ Measuring tapes
Brass $$Fe, Cr, Ni$$ Domestic utensils
Rolled gold $$Pb, Sn, Sb$$ Common articles
Invar $$Cu, Ni$$ Soldering
Stainless steel $$Pb, Sn$$ Airships
Solder $$Al , Mg$$ Printing types
Type metal $$Fe, Ni$$ Artificial jewellery
Magnalium $$Cu, Zn$$ Electrical resistances

Match the columns $$X_i$$, $$Y_i$$ and $$Z_i$$
where i=1,2,3........8 from top to bottom. Ex- $$X_4$$ stands for Invar & $$Z_6$$ stands for Artificial jewellery.

Constantan is a Nickel-Copper based alloy wire that has a high resistivity and is mainly used for thermocouples and electrical resistance heating.$$\Rightarrow X_1=Y_4=Z_8$$

Brass is an alloy made primarily of copper and zinc. It is used in musical instruments.$$\Rightarrow X_2=Y_8=Z_3$$

Rolled gold is a composition of Copper and aluminium. It is mainly used in making cheap ornaments. $$\Rightarrow X_3=Y_1=Z_7$$

Invar is a single-phase alloy, consisting of around 36% nickel and 64% iron. It is used in making measuring tape. $$\Rightarrow X_4=Y_7=Z_1$$

Stainless steel is an iron alloy with added elements such as chromium, nickel, silicon, manganese, nitrogen, and carbon. It is mainly used in making domestic utensils. $$\Rightarrow X_5=Y_2=Z_2$$

Solder is a metal alloy usually made of tin and lead. It is used in soldering. $$\Rightarrow X_6=Y_5=Z_4$$

Type metal is an alloy of lead, tin, and antimony. It is used in printing types. $$\Rightarrow X_7=Y_3=Z_6$$

Magnalium is an aluminium alloy with 5% magnesium and 95% aluminium. It is used in Air space. $$\Rightarrow X_8=Y_6=Z_5$$

$$\mathbf{\Rightarrow \ \therefore X_1=Y_4=Z_8,\ X_2=Y_8=Z_3,\ X_3=Y_1=Z_7,\ X_4=Y_7=Z_1,\ X_5=Y_2=Z_2,}$$

$$\mathbf{X_6=Y_5=Z_4,\ X_7=Y_3=Z_6,\ X_8=Y_6=Z_5}$$

Name two metals which are used :
(a) for making electric wires.
(b) for making domestic utensils and factory equipments.
(c) for making jewellery and to decorate sweets.

(a) Aluminium and copper are two metals which are used for making electric wires.

(b) Copper and aluminium are two metals which are used for making domestic utensils and factory equipment's.

(a) What happens when calcium reacts with water? Write the chemical equation of the reaction of calcium with water.

(b) Write the chemical equation of the reaction which takes place when iron reacts with dilute sulphuric acid. What happens when the gas produced is ignited with a burning matchstick?

(a) Calcium reacts with cold water to form calcium hydroxide and hydrogen gas.

Reaction: $$ Ca(s) + 2H_2O(l) \longrightarrow Ca (OH)_2 (aq) + H_2(g) $$

(b) When irons react with dilute sulphuric acid, it forms iron sulfate and hydrogen gas.

Reaction: $$ Fe(s) + H_2SO_4 (aq) \rightarrow FeSO_4 (aq) + H_2 (g) $$

When hydrogen gas is ignited with a burning matchstick, it produces a 'pop' sound.

Name two characteristic physical properties of metals that are not exhibited by non-metals.

Malleability(ability to be beaten into thin sheets) and Ductility(ability to be drawn into wires) are two characteristic physical properties of metals that are not exhibited by non-metals.

Explain why the surface of some metals acquires a dull appearance when exposed to air for a long time.

The surface of some metals acquires a dull appearance when exposed to air for a long time because metals from a thin layer of oxides, carbonates or sulphide on their surface by the slow action of various gases present in the air that make the dull appearance

(a) What type of oxides are formed when non-metals react with oxygen? Explain with an example.

(b) What type of oxides are formed when metals combine with oxygen? Explain with the help of an example.

(a) When non-metals react with oxygen, they form acidic oxides or neutral oxides.

Example: Carbon reacts with oxygen to form an acidic oxide called carbon dioxide.

Hydrogen reacts with oxygen to form neutral oxide called water.

(b) When metals combine with oxygen, they form basic oxides

Example : Sodium reacts with oxygen to form a basic oxide called sodium oxide.

Name two non-metals that are both brittle and nonductile.

Two non-metals that are both brittle and nonductile are sulfur and phosphorus.

Which property of graphite is utilised in making electrodes?

Graphite is used in making electrodes because it is a good conductor of electricity due to the presence of free electrons. One valence electron of each carbon atom remains free and thus it is a good conductor of electricity.

Which property of copper and aluminium makes them suitable :
(a) for making cooking utensils and boilers?
(b) for making electric wires?

(a) High thermal conductivity is the property of copper and aluminium makes them suitable for making cooking utensils and boilers.

(b) High electrical conductivity is the property of copper and aluminium makes them suitable for making electric wires.

State one use each of the following metals:

Copper, Aluminium, Iron, Silver, Gold, Mercury.

(a) Copper: Copper is use to make wires to carry electric current.

(b) Aluminium: Aluminium foils are used in packaging of food materials.

(d) Silver: It is used to make jewellery.

(e) Gold: It is used to make jewellery.

(f) Mercury: Mercury is used in thermometers.

State fives uses of metals.

Uses of metals:

(a) Lead metal is used in making car batteries.

(b) Zinc is used for galvanizing iron to protect it from rusting.

(d) Copper and aluminium metals are used to make electrical wires.

(e) Aluminium is used to make aluminium foil for packaging materials.

Name a metal which is soft and a non-metal which is hard.

Sodium is a soft metal. It can even be cut with a knife.
Diamond is an extremely hard non-metal, which is an allotrope of carbon.

Name a non-metal which is good conductor of electricity.

Graphite, an allotrope of carbon, is a non-metal and a good conductor of electricity.

What is do we mean by saying that metals are sonorous ?

Metals are sonorous because they make sound when we strike on them.

(a) Define non-metals. Give five examples of non-metals.
(b) Name a non-metal which conducts electricity.
(c) Name a non-metal having lustre (shining surface).
(d) Name a non-metal which is extremely hard.
(e) How do non-metals react with oxygen? Explain with an example. Give equation of the reaction involved. What is the nature of the product? How will you demonstrate it?

(a) Non-metals are the elements that do not conduct heat and electricity and are neither malleable nor ductile. Example: carbon, sulphur, phosphorus, silicon, oxygen, etc.

(b) Carbon is a non-metal which conducts electricity.

(d) Diamond an allotrope of carbon is a non-metal which is extremely hard.

(e) Non-metals reacts with oxygen to form acidic oxides or neutral oxides. Carbon burns in air to form carbon dioxide.

Reaction: $$ C(s) +O_2(g) \rightarrow CO_2(g) $$

The nature of the product formed is acidic. When carbon dioxide dissolves in water, it forms carbonic acid. It turns blue litmus to red which shows it is acidic in nature.

State any five physical properties of metals and five physical properties of non-metals.

Properties of metals:

(i) Metals are malleable i,e, they can be beaten into thin sheets with a hammer.

(ii) Metals are ductile i.e. they can be drawn into thin wires.

(iii) Metals are good conductors and heat and electricity.

(iv) Metals are lustrous.

(v) Metals are generally hard.

Properties of non-metal:

(i) Non-metals are non-malleable i,e, they cannot be beaten into thin sheets with a hammer.

(ii) Non-metals are non-ductile i,e, they cannot be drawn into thin wires

(iii) Non-metals are bad conductors of heat and electricity

(iv) Non-metals are non-lustrous.

(v) Non-metals are generally soft.

You are given a dry cell, a torch bulb with holder, wires and crocodile clips. How would you use them to distinguish between samples of metals and non-metals?

We would create an apparatus using a dry cell, a torch bulb fitted in holder and some connecting wires with crocodile clips and connect them to make an electric circuit.

Then insert a piece of sulphur between the crocodile clips and the bulb does not light up at all. This means that sulphur does not allow the electric current to pass through it.

Now insert a piece of copper between the crocodile clips and the bulb will light up.

This observation shows that non metals (ex: sulphur) do not conduct electricity and metal (ex: copper) conduct electricity.

What do you mean when you say that metals are lustrous?

Metals have a characteristic shine which is known as the metallic lustre. This lustre is present because the surface of the metal can reflect the rays of light which are incident on it. Hence metals are known to be lustrous.

What is meant by malleability? Name two most malleable metals.

The property of metals which allow them to be beaten into thin sheets is called malleability. Gold and silver are the most malleable metals.

Compare the properties of metal and non-metals a with respect to:
(i) malleability
(ii) ductility
(iii) electrical conductivity

(i). Malleability-metals show this property but non-metals don't.

(ii). Ductility- Metals show this property but non-metals don't.

(iii). Electrical conductivity- Metals are good conductors of electricity whereas non-metals are bad conductors except graphite.

Name two non-metals which are lustrous.

Iodine and carbon are non-metals that are lustrous. Note that carbon is lustrous only in certain forms like diamond, and graphite.

Write three general physical properties of metals.

Metals are sonorous, i.e. they produce ringing sounds when struck.
They are malleable, which means they can be beaten into thin sheets.
They are ductile as they can be drawn into thin wires.

Mercury, however, lacks these properties as it is a liquid metal.

What is meant by ductility? Name two most ductile metals.

The ability of the metals to be drawn into thin wires is known as ductility. Gold and platinum are the most ductile metals.

State two physical properties based on which metals can be distinguished from non-metals.

Metals are malleable and ductile that is they can be drawn to wires and can be hammered but non-metals are neither malleable nor ductile.

Fill in the following blanks with suitable words:

The elements which are sonorous are called________.

The elements which are sonorous are called metals.

Name two metals which are best conductors of heat.

Silver and Copper are the best conductors of heat.

Why is sodium a metal whereas carbon a non-metal?

Sodium is a metal because it is a good conductor of electricity, malleable and ductile. It can lose electrons easily from the valence shell whereas carbon is a bad conductor of electricity, not lustrous or malleable. It does not lose electrons easily.

Which property of graphite is utilized in making electrodes?

Graphite is a good conductor of electricity. Due to this property, graphite is utilized in making electrodes.

Why will the colour of heated copper powder become black when air is passed over it?

When copper powder is heated in the presence of air, black copper oxide is formed.
$$\underset{copper\,powder}{2Cu(s)}+\underset{oxygen(from\,the\,air)}{O_2(g)}\xrightarrow[]{heat}\underset{copper\,oxide(Black)}{2CuO(s)}$$

Which of the following metals will melt at body temperature?
Gallium, Magnesium, Caesium, Aluminium

In these given metals, the two metals which melt at body temperature are gallium and cesium. These two metals have melting points nearer to $$37^ \circ C$$.

What is the nature of non-metal oxide?

When non-metals react with oxygen the non-metallic oxide is formed. Non-metallic oxides are acidic. They form an acidic solution when dissolved in water, turning blue litmus to red colour. Non-metal oxides like $$CO _2$$

and $$SO_2$$ react with water and give acids.

Explain why the surface of same metals acquires a dull appearance when exposed to air for a long time.

The surface of some metals acquires a dull appearance when exposed to air for a long time due to the formation of a thin layer of oxide, carbon or sulphide on their surface by the slow action ofthe various gases present in air.

Name one metal and non-metal that exist in the liquid state at room temperature. Name two metals having melting point less than $$310 K (37^{o}C)$$

Metal: Mercury (Hg); Non-metal: Bromine (Br)
Two metals with a melting point less than $$310 K$$ are Cesium (Cs) and Gallium (Ga).

Explain the following statement:
At ordinary temperature, the surface of metal such as magnesium, aluminium, and zinc, etc. is covered with a thin layer. What is the composition of this layer? State its importance.

At ordinary temperature, the surface of the metal is covered with a thin layer of oxide. This thin layer is the protective oxides layer (like $$MgO, Al_2O3$$, and $$ZnO$$) which prevents the metal from further oxidation.

A purple-colored non-metal forms a brown solution in alcohol which is applied on wounds as an antiseptic. Name the nonmetal.

The tincture of iodine is the brown-colored solution that is formed with Iodine ( a purple-colored non-metal). It is used as an antiseptic to apply to wounds.

Which liquid metal is used in thermometers?

Mercury is the only metal in the liquid state at room temperature. It's used in thermometers because it has a high coefficient of expansion.

Why are bells made of metals?

Metals produce ringing sound, which is their sonorous property. Thus, metals are used to make bells.

Which non-metal is used to disinfect water?

Chlorine is a non-metal and possesses the quality of killing germs present in water. Hence, is used for disinfecting water.

Name two soft metals which can be cut with a knife.

Following metals are soft metals and can be cut easily with a knife-
Potassium
Sodium.

Name two major non-metals which are present in fertilisers and enhance the growth of plants.

Following are the two major non-metals essential for fertilizers-
(i) Phosphorus and (ii) Nitrogen

Which non-metal is essential for our life and all living beings which we inhale during breathing?

Oxygen is a non-metal essential for our life and all living beings inhale during breathing. Oxygen gas in the air is essential for breathing to survive.

Which of the following metals can displace the other two metals from their salt solutions?
zinc, iron, copper

Following is the reactive order of the given
$$ Zinc> Iron> Copper $$
As Zinc metal has the most reactive property, it can displace other two metals from , their salt easily.

A metal A, which is used in thermite process, when heated with oxygen gives an oxide B, which is amphoteric in nature. Identify A and B. Write down the reactions of oxide B with $$HCl$$ and $$NaOH$$.

Metal A is aluminium and B is $$Al_2O_3$$.
Reaction of aluminium oxide with $$HCl$$:
$$Al_2O_3 + 6HCl \rightarrow + 3H_2O$$
Reaction of aluminium oxide with $$NaOH$$:
$$Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O$$

Iron is more reactive than copper. Write an activity to show this.

Material required- Copper sulphate solution, Iron nail, test tube.

Method- In the test tube, pour copper sulphate solution. Drop the iron nails it and wait for the reaction to take place.

Observation- Solution turns blue. The nail which is in the contact with the solution turns reddish-brown.

Conclusion- The above process can be understood by the following equation-
$$ Fe+CuSO_{4}\rightarrow FeSO_{4}+Cu $$
Thsi reaction is a type of displacement reaction.

Is wood a good conductor of electricity?

No, wood is a good insulator of electricity. The natural fiber of wood is in itself a hollow cell which provides a minute air space, hence wood act as insulating unit.

Paheli bought a statue made of copper. To her surprise, it acquired a dull green coating after a couple of months. Explain the reason.

Copper on reaction with moist air forms copper hydroxide and copper carbonate and thus acquires that dull green colour which is also known as corrosion of copper.
1652421_1790645_ans_765e6e19803c4cd9a5ec600c97807359.png

1652421_1790645_ans_765e6e19803c4cd9a5ec600c97807359.png

When a mixture of copper sulphate and zinc granules is mixed in water, the blue colour of copper sulphate disappears and a powdery red mass is deposited at the bottom of the beaker. This is which type of reaction?

This is a displacement reaction. In this reaction, zinc metal replaces copper metal from copper sulphate. The powdery red mass is that of copper.

$$Copper\ sulphate\ (blue) + Zinc \rightarrow Zinc\ sulphate + Copper\ (red)$$

Which metal generally used for making jewelry?

Silver is a softer metal than gold, titanium, and platinum, and does not have the hardness of the other metals. Sterling silver is $$92.5 \%$$ pure silver and is usually stamped as $$925$$. Silver is a popular metal for use in jewelry such as earrings, pendants, bracelets, necklaces, and fashion rings.

Property by virtue of which metals can be beaten into thin sheets is called

Property by virtue of which metals can be beaten into thin sheets is called Malleability

Give two examples each of the metals that are good conductors and poor conductors of heat respectively.

Iron and copper are good conductors of heat and electricity.

Lead and mercury are poor conductors of heat and electricity.

Name one metal and one non-metal that exist in liquid state at room temperature. Also, name two metals having melting point less than $$310 K (37^0 C)$$

Mercury (metal) and bromine (non-metal) exist in liquid state at room temperature. Caesium and gallium are metals with melting point less than 310 K.

Out of Metals and Non-Metals, which is hard, ductile, malleable, and sonorous?

Metals are hard, ductile, sonorous and malleable.

Name a metal which is liquid at room temperature.

Mercury is a metal which is liquid at room temperature.

Name a metal that reacts with acid as well as base to form hydrogen gas.

Zinc metal, reacts with both acid and base to produce hydrogen gas.
1652670_1790917_ans_a6338f7ab774461bbb09135d894a4714.png

Find out the names of three metals and three non-metals from the box given in Fig ;

Metals:

1) Copper

2) Iron

3) Aluminium

Non-Metals:

1) Oxygen

2) Sulphur

3) Carbon

Property of metal by the virtue of which it can be drawn into wires called?

Ductility is the property of metals through which it can be drawn into wires.

Fill in the blanks to complete the following paragraph.

The name of the product formed in the reaction of Sulphur and $$Oxygen$$ is Sulphur dioxide gas. When Sulphur dioxide is dissolved in $$water$$. Sulphurous acid is formed. The Sulphurous acid turns $$blue$$ litmus paper to $$red$$. Generally, oxides of $$non-metals$$ are acidic in nature. After completing the paragraph write two questions that you can raise on the basis of this information.

List some objects made using metal.

Some of the objects made from metal are :

Jewellery
Wires
Utensils
Foil paper
Statues
Gates
Nails

Non-metals are usually poor conductors of heat and electricity. They are non- lustrous, non-sonorous, non-malleable, and are colored. Name a non-metal which exists as a liquid at room temperature.

A non-metal which exists as a liquid at room temperature is Bromine ($$Br$$).

Non-metals are usually poor conductors of heat and electricity. They are non-lustrous, non-sonorous, non-malleable and are coloured.
Name a lustrous non-metal.

An example of lustrous non-metal is $$\text {Iodine}$$.

Why do silver articles turn black when kept in the open air for a few days? Name the phenomenon involved.

Metals such as silver when attacked by substances around it such as moisture, acids, gases, etc, tend to corrode and this phenomenon is called corrosion. Due to corrosion, silver turns black.

A metal M does not liberate hydrogen from acids but reacts with oxygen to give a black colour product. Identify M and black coloured product and also explain the reaction of M with oxygen.

Copper does not react with acids. But copper gives black coloured copper oxide when it reacts with oxygen. Hence, M is copper and black coloured product is copper oxide.
$$2Cu + O_2 \rightarrow 2CuO$$

Give four examples of non-metallic elements.

Non-metals lack the properties of metals.

Examples of non-metallic elements: Hydrogen, oxygen, nitrogen, and carbon.

Non-metals are usually poor conductors of heat and electricity. They are non- lustrous, non-sonorous, non-malleable, and are colored. The allotropic form of a non-metal is a good conductor of electricity. Name the allotrope.

The allotrope of $$C$$ atom that satisfies all the above properties is graphite.

Graphite is the allotropic form of carbon and it is a good conductor of electricity.

An element forms an oxide $$A_2O_3$$ which is acidic in nature. Identify A as a metal or non-metal.

Oxides of non-metals are acidic in nature. Hence, A is a non-metal.

Name a non-metal which is required for combustion.

Oxygen is required for combustion. It is a supporter of combustion and is needed for burning fuel.

Non-metals are usually poor conductors of heat and electricity. They are non-lustrous, non-sonorous, non-malleable, and are colored or colorless. Name a non-metal which is known to form the largest number of compounds.

A non-metal that is known to form the largest number of compounds is Carbon ($$C$$).

Give reason :
Gold is mixed with copper and nickel.

Pure gold is a very soft metal. It cannot be molded into ornaments so it is mixed with copper and nickel so that it becomes harder and a bit cheaper.

Name a metal used in making electric cables.

Copper is the metal used in making electric cables. Copper is ductile and a very good conductor of heat and electricity. This is the reason that copper is used in making electric cables.

Name a non-metal that is used for filling electric bulbs.

The non-metal that is used for filling into electric bulbs is Argon. Argon is used in electric bulbs because it helps maintain the inert atmosphere and also eliminates oxygen, which would corrode (rusting) the heated filament on contact.

Give two uses of Tungsten.

$$\bullet$$ It is used in making electrodes.
$$\bullet$$ It is used as filament in bulbs.

Name a metal that is brittle.

Zinc is a lustrous bluish-white metal. It is found in the group $$IIb$$ of the periodic table. It is brittle and crystalline at ordinary temperatures, but it becomes ductile and malleable when heated between $$110°C$$ and $$150°C$$.

Name a non-metal that is used for cancer therapy.

Radon is the non-metal that is used for cancer therapy. It's a colourless, odourless and radioactive noble gas.

Name a non-metal that is used to kill germs in water.

The non-metal that is used to kill germs in water is chlorine

Give four differences between metals and non-metals with reference to their:
(a) Melting point and boiling point
(b) Conductivity of heat and electricity
(c) Malleability
(d) Solubility

$$\textbf{Properties}$$	$$\textbf{Metals}$$	$$\textbf{Non-metals}$$
(a) Melting point and boiling point	Metals have high melting points and boiling points.	Non-metals have low melting and boiling points.
(b) conductivity of heat and electricity	They are good conductors of heat and electricity.	Non-metals are bad conductors of heat and electricity.
(c) Malleability	Metals are usually malleable.	All non-metal are non-malleable.
(d) Solubility	Metals are generally insoluble in water and other organic solvents.	Non-metals can be soluble or insoluble in water or other solvents.

A non-metal used to purify water is _______ .

A non-metal used to purify water is $$\underline{\textbf{chlorine}}$$.

Fill in the blank:
The most ductile metal is ______.

The most ductile metal is $$\underline{\textbf{silver}}$$.

What do you observe when calcium is heated and then tested with moist blue and red litmus - paper?

When calcium is heated, it reacts with oxygen to form calcium oxide. When calcium oxide reacts with water, it turns into calcium hydroxide, which is an alkali. So, it turns moist red litmus blue. There will be no effect on moist blue litmus paper.

$$2 Ca + O_2 \rightarrow 2 CaO$$

$$CaO + H_2O \rightarrow Ca(OH)_2$$

Name a gaseous non-metal, having greenish yellow colour.

Chlorine is a gaseous non-metal having greenish yellow colour.

Name a non-metal which is ductile.

Carbon fibre is a non-metal which is ductile.

Name a metal with dull appearance.

Lead is a metal with dull appearance.

Name a metal which can be cut with a knife.

The metal that can be cut with a knife is Sodium. It is a soft metal.

Name a non-metal that is found in plants.

Magnesium is a non-metal found in plants. It helps them grow.

State any five physical properties of a non-metal.

Physical properties of a non-metal:

1. State: Non-metals are generally gases at room temperature.

2. Hardness: Non-metals are not hard (being gases). In case of solid non-metals, they are hard but brittle in nature.

3. Conductivity: Non-metals are poor conductors of heat and electricity except graphite.

4. Malleability: Non-metals are non-malleable, i.e., they cannot be beaten into thin sheets.

5. Ductility: Non metals are non-ductile, i.e., cannot be drawn into wires.

Name a metal which is a bad conductor of heat and electricity.

Tungsten is a metal which is a bad conductor of heat and electricity.

Name a metal which is lighter than water.

Sodium is a metal which is lighter than water because density of sodium$$(0.971 g/cm^3)$$ is less than water$$(1g/cm^3)$$.

Other metallic elements which are lighter than water are lithium and potassium.

Name a metal which is not malleable.

Certain metals like zinc, arsenic, mercury, antimony are non – malleable in nature.

A student has been collecting silver coins and copper coins. One day she observed a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings? Write the names of black and green coatings.

Silver gets tarnished when exposed to the atmosphere which contains pollutant $$H_{2}S$$ and forms a black coating of $$Ag_{2}S$$.
Copper forms a green deposit on its surface when exposed to moist air. This is usually basic $$CuSO_4$$.

Name two metals which are soft.

Sodium and potassium are soft.

Name a metal which lacks ductility.

Mercury is a metal that lacks ductility because it is neither malleable nor ductile.

Name a non-malleable metal.

Mercury is a non-malleable metal. That's because it is liquid at room temperature and so, cannot be hammered into thin sheets.

Name two metals which are liquid at room temperature.

Mercury and gallium are metals that are liquid at room temperature.

Name a metal that is brittle.

Zinc is a metal that is brittle. It is brittle and crystalline at ordinary temperatures, but it becomes ductile and malleable when heated between $$110°C$$ and $$150°C$$.

Write balanced equations for the following
Aluminium reacts with fused sodium hydroxide.

$$2Al+6NaOH \to 2Na_2AlO_3+3H_2$$

Why do gold ornaments look new even after several years of use?

Gold is the most unreactive metal so it does not react with air or water or other gases in atmosphere, so gold does not corrode. That is why gold looks new after several years of use.

What is the chemical name of the green coating formed on copper when it is exposed to air?

Copper reacts with moist carbon dioxide in the air and slowly loses its shiny brown surface and gains a green coat. This green substance is basic copper carbonate.

Which metal is used for:
(a) making pipes, buckets, and water tanks
(b) lithographic plants for printing
(c) making face creams

(a) Galvanized iron sheets protect the iron from rusting hence used in making pipes, buckets, water tanks, and many more.
(b) Zinc:- In lithography, the printing surface needs to be smooth, flat plane. As zinc metal has these properties hence used in lithographic plants for printing.
(c) Zinc:- Zinc metal has antiseptic properties hence used in face creams.

The oxides of non metals are generally ______ in properties.

The oxides of non metals are generally $$\underline{ acidic} $$ in properties.

Write any four uses of metals.

$$\text{Use of metals:}$$

1. To make cooking wares.

2. In making electric appliances, electric wires, fridge etc.

3. Sheets of aluminium and iron for buildings materials.

4. In manufacturing jewellery from gold, silver, coins and from copper, aluminium etc.

Explain the difference between Metals and non-metals .

Physical Properties	Metals	Non-metals
Malleability and ductility	They can be beaten into sheets and wires.	They cannot form sheets or wires.
Sonority	Metals are sonorous, they produce a ringing sound on beating.	They are non-sonorous.
Conduction	They conduct heat and electricity.	They do not allow heat and electricity to pass through them.

Nature of oxides	Metallic oxides are basic in nature.	Oxides of non-metals are acidic.
Reaction with water	Metals react with water	Non-metals do not react with water.
Reaction with acids	Metals react with acids to produce hydrogen gas.	They generally do not react with acids.

Identify the odd term.
Ductility, brittleness, sonority, malleability

Brittleness is an odd one out because it is a property of non-metals, and the rest are the properties of metals.

Write a scientific reason.
Copper vessels are cleaned with lemon.

Copper vessels get tarnished. They form a layer of copper oxide which is basic in nature. When lemon juice, which is acidic in nature, is added to it, a neutralization reaction takes place, resulting in the formation of salt and water. The salt formed is removed by washing. So, copper vessels are cleaned using lemon.

Why is the metal good conductor of electricity?

Metals are the good conductor of electricity $$\text{because they have free electrons.}$$

Why is aluminium used for making cooking coil?

Aluminium is used for making cooking coil $$\text{as it is very light weight metal, resistant to corrosion and is good conductor of heat.}$$

Why do we store phosphorus in water?

Phosphorus is a very reactive nonmetal. It catches fire if exposed to air. So, to prevent the contact of phosphorus with atmospheric oxygen, it is stored in water.

Thin strips of magnesium, copper and iron are taken.Write down what happens when these metals are treated as follows:
Heated in presence of air

When we heat magnesium, copper and iron in presence of air they form respectively oxides.
$$Mg+\frac{1}{2}O_{2}\rightarrow MgO$$
$$Cu+\frac{1}{2}O_{2}\rightarrow CuO$$
$$2Fe+\frac{3}{2}O_{2}\rightarrow Fe_2O_3$$

Write the equation of copper with moist air.

During long exposure of Copper in moist air, a green layer of Copper Carbonate $$(CuCO_3)$$ and Copper hydroxide $$(Cu(OH)_2)$$ is formed on the surface of copper metal.

$$ 2Cu+H_2O+CO_2+O_2 \rightarrow Cu(OH)_2+CuCO_3 $$

$$\textbf{Note:}$$ Here mixture of $$H_2O,CO_2$$ and $$O_2$$ is considered as moist air.

What do you mean by malleability?

Malleability is the property of metals by which metals can be beaten into thin sheets. Metals like gold, silver, copper, iron, etc exhibit this property.

Give a reason for the following:
Iron is used in constructing bridges and houses.

Iron is used in constructing bridges and houses because iron is a $$\text{hard, strong, and rigid metal.}$$

Gold wires are used in ornaments. Which property of gold is used in ornaments?

The property of gold used in making ornaments is ductility and luster. It is also one of the most unreactive metals.

Write the equation for reaction of copper sulfate with zinc.

The equation for copper sulphate's reaction with zinc:

$$ CuSO_4+Zn \rightarrow Cu+ZnSO_4 $$

This is a displacement reaction in which zinc is replacing copper from the metal salt.

Explain the meanings of malleability and ductility.

Malleability: Some metals can be beaten into thin sheets. This property is called Malleability.
Ductility: The ability of metals to be drawn into thin wires is called ductility.

Give a reason: Lemon pickles should not be stored in aluminum utensils.

Lemon pickles are acidic in nature. When aluminium comes in contact with acidic components of food, it will produce aluminium salt and hydrogen gas, which will spoil the food. So lemon pickles should not be stores in aluminium utensils.

Account for: Copper is malleable and ductile while sulphur is not.

Copper is metal and has strong metallic bond, that is why it is malleable and ductile. Sulphur is non-metal and has weak intermolecular force of attraction therefore it is brittle.

Sodium cannot be kept open in atmosphere air, and cannot be stored under water. So, it is stored in kerosene. Give an explanation for the above statements with its chemical equation.

Sodium reacts vigorously with water and oxygen.

$$4Na(s) +O_2(g) \to 2Na_2O(s)$$

$$2Na(s) +2H_2O(l) \to 2NaOH(aq)+H_2(g)$$

This $$NaOH$$ reacts with $$CO_2$$ in the atmospheric air and forms sodium carbonate.

$$2NaOH(s) +CO_2(g) \to Na_2CO_3+H_2O (l)$$

To avoid the reaction with $$O_2, H_2O$$ and $$CO_2$$ sodium is stored in kerosene.

Name the acid formed when sulphur dioxide dissolves in water.

When sulphur dioxide dissolves in water sulfurous acid is formed. It's formula is $$H_2SO_3$$.

Give reason for the following:

Aluminum is used to make electrical wires.

Aluminum is used to make electrical wires because aluminum is a metal with low resistance and good conductivity.

Some metals are listed below. Complete the table by identifying the different uses and the properties which are responsible for the same.
Metal Use Property
Gold $$\bullet$$
Copper $$\bullet$$
Aluminium $$\bullet$$
Zinc $$\bullet$$
Iron $$\bullet$$

Metal Use Property

Gold To make ornaments Ductility

To make coins Malleability

Copper To make utensils Thermal conductivity

To make electric wire Electrical conductivity

Aluminium To make utensils Thermal conductivity

To make aluminium foil Malleability

Zinc To make thin sheets Malleability

In electric equipments Electrical conductivity

Iron To make farming tools Hardness

To make utensils Thermal conductivity

Cut a small sodium metal piece into two, watch it.
What change occured on the surface of sodium metal?

Sodium is soft with a bright shiny surface, however when it is cut into pieces it reacts with the air and becomes dull due to the formation of sodium oxide.

How does oxygen react with non-metals?
$$C + O_2 \rightarrow $$..........
$$2H_2 + O_2 \rightarrow$$.............

Oxygen reacts with non-metals such as carbon and hydrogen to produce carbon dioxide and water respectively,
$$C + O_2 \rightarrow CO_2$$
$$2H_2 + O_2 \rightarrow 2H_2O$$

Lustre of aluminium utensils disappear after some days. Why?

Aluminium reacts with atmospheric air and Aluminium oxide is formed, this process takes place slowly. Hence Aluminium utensils lose their lustre.

Give reason for the following,
$$CuSO_4$$ solution is not stored in iron vessels.

From the activity series, it is clear that Iron ($$Fe$$) is more reactive than copper ($$Cu$$), So it can displace copper from its solution.

As iron ($$Fe$$) can displace copper from copper sulphate solution and forms ferrous sulphate ($$FeSO_4$$), hence copper sulphate solution is not stored in iron vessels.

What are the similarities between iron, copper and aluminium?

Similarities between iron, copper and aluminium are:

a) They all have lustre.

b) They are all metals.

c) They are hard.

Metals generally occur in solid-state and are hard. Name a metal that exists in a liquid state and a metal that is soft and can be cut with a knife.

Mercury is a metal that exista in liquid state.

Sodium and potassium are soft and can be cut with knife.

Collect the following materials: an iron nail, an aluminium wire, a pencil lead, a copper wire. Beat them hard using a hammer. Which of them can be flattened? What is your conclusion from this experiment?

Iron nail, aluminum, and copper wire can be flattened, but pencil lead cannot be flattened.

Conclusion: Iron, aluminium, and copper are metals, and metals have the property of malleability. So, they can be drawn into a sheet.

Which is the metal used for making filament of bulb? Which property is made use of it?

Tungsten metal is selected for making filaments of lamp bulbs because it has a high melting point, due to which it does not melt even when it is heated to high temperatures due to the passage of electric current.

How will the properties of metals like hardness, malleability, thermal conductivity, electrical conductivity, and ductility be used?

Situations using properties of metals are :

$$\bullet$$To make farming tools

$$\bullet$$ To make aluminium foil,
$$\bullet$$ To make utensils
$$\bullet$$ To make electrical equipments
$$\bullet$$ To make ornaments.

Which metal is seen in liquid state?

Generally all the metals are found in the solid state at room temperature. The exception to this is mercury. $$\textbf{Mercury}$$ is found in liquid state at room temperature. Whereas non metals are found in the 3 states at room temperature i.e. solid, liquid and gas.

Select the metal which does not react with air:
Copper, iron, gold, magnesium, platinum, sodium, silver.

Gold, silver, platinum have a very low reactivity and so do not react with air.

Does any immediate change occur when a bright nail is exposed to air? What happens to it after a few days?

Immediate change does not occur. After a few days it reacts slowly with air and gets a coating of oxide.

What is the property of metal caused for shining appearance?

Metals are lustrous in nature, having shiny appearance.

Fill the table
Use Property
To make utensils
To make aluminium foil
To making farming tools
To make electric wire
To make bells

Use Property

To make utensils thermal conductivity
To make aluminium foil malleability
To making farming tools hardness
To make electric wire electrical conductivity
To make bells sonority

Which among the metals is stored in kerosene?
(a) Sodium
(b) Iron
(c) Tungsten
(d) Chromium
Why is it stored in kerosene?

a. Sodium is stored in Kerosene.

Reason : Sodium is a highly reactive metals and react vigorously with the oxygen, carbon dioxide and moisture present in the air such that it may even cause a fire. To prevent this explosive reaction, Sodium is kept immersed in kerosene because Sodium doesn't react with kerosene.

$$2$$ mL of sodium hydroxide solution is added to a few pieces of granulated zinc metal taken in a test tube. When the contents are warmed, a gas evolves which is bubbled through a soap solution before testing. Write the equation of the chemical reaction involved and the test to detect the gas. Name the gas which will be evolved when the same metal reacts with the dilute solution of a strong acid.

1) $$Zn+2NaOH\rightarrow Na_2ZnO_2+H_2$$
2) When a burning splinter is brought near the gas, it burns with a Pop Sound.
3) Gas- Hydrogen / $$H_2$$

Fill in the blanks:
Phosphorus is a very ______ non-metal.

Phosphorus is a very $$\underline {reactive}$$ non-metal. When exposed to air, it catches fire spontaneously. So, it is kept submerged in water to avoid contact with oxygen in air.

A reddish brown coloured metal, used in electrical wires, when powdered and heated strongly in an open china dish, its colour turns black. When hydrogen gas is passed over this black substance, it regains its original colour. Based on the above information answer the following questions:
(a) Name the metal and black coloured substance formed
(b) Write balanced chemical reactions for both the reactions

(a) The name of the metal is copper (Cu) and the black coloured substance formed is copper oxide.

(b) The balanced chemical reactions for both the reactions are as follows:

When powdered copper is heated strongly in the presence of oxygen to form copper oxide

$$2Cu(s) + O_2(g)\rightarrow 2CuO(s)$$

When hydrogen gas is passed over copper oxide, it produces copper metal and water.

$$CuO(s) + H_2(g)\rightarrow Cu(s) + H_2O(l)$$

$$Additional Information:$$

Hydrogen is above Copper in the reactivity series, hence Hydrogen is more reactive than Copper. Therefore, Hydrogen can replace Copper from $$CuO$$

Give reasons for the following:
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.

a) Aluminium is one of the less reactive metals, so it does not react with food items and does not alter the taste. Moreover, being a metal, aluminium is highly malleable and can be made into very thin foils which are perfect for wrapping food.

b) Immersion rods for heating liquids are made up of metallic substances because metals are good conductors of heat and electricity. The immersion rod needs an electric supply to get heated and in turn to heat liquids.

c) Copper is less reactive than zinc. This can be confirmed from the electrochemical or activity series in which $$Zn$$ has a lower reduction potential than $$Cu$$. This means $$Zn$$ is more reactive than $$Cu$$. This is the reason, copper cannot displace zinc from its salt solution.

d) Sodium and potassium are highly reactive metals. If kept in open, they readily react with oxygen in the atmosphere. The reaction is so quick that sodium and potassium easily catch fire when exposed to air. To prevent accidental fire, they are stored in kerosene.

Match the elements given, in column I correctly with their respective uses given in column II.

List I	List II
Gold	Jewellery
Iron	Machinery
Aluminium	Wrapping food
Carbon	Fuel
Copper	Electric wire
Mercury	Thermometers

Name :
The non-metal which is lustrous.
The non-metal which is liquid.
Non-metal which is conductor of electricity.
The non-metal which is hardest natural substance known.

The non-metal which is lustrous and shiny is graphite, black phosphorous.

The non-metal which is liquid is bromine at room temperature.

The non-metal which is conductor of electricity is graphite.

Diamond is the natural hardest non metal known.

Is the gold a inactive or non reactant metal ? If yes then how and why?

2041219_1359861_ans_2ef53585f27f4e3bac2025651c5d9833.jpg

What will happen when copper metal is put in iron sulphate solution? Write the chemical reaction involved.

No reaction occurs when copper metal is put in iron sulphate solution. A less reactive metal cannot displace a more reactive metal from its metal salt. So, copper being less reactive than iron, will not displace iron. Hence, no reaction will occur.

Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(a) How will she find the acidic/basic nature of the gas?
(b) Write down word equation of all the reactions taking place in this process.

(a) Saloni needs to add some water in the test tube in which the gas is collected. She needs to cover the tube and shake it well. Now, she will test the solution with both red and blue litmus. Blue litmus turns to red which shows that the gas is acidic in nature.

(b) Carbon in charcoal reacts with oxygen to form carbon dioxide gas.
$$Carbon +Oxygen \longrightarrow Carbon\ dioxide$$

Carbon dioxide gas reacts with water to form carbonic acid which is acidic in nature and turns blue litmus red.
$$Carbon\ dioxide + Water \longrightarrow Carbonic\ acid$$

The luster of magnesium disappears quickly when it is placed in an open space. Why?

When magnesium is kept in open space, it reacts with oxygen present in the air and, a light coat of magnesium oxide is formed. This layer covers the magnesium metal and, so it appears dull.

Fill in the blanks:
Metals combine with_____ to form metal oxides.

Metals combine with oxygen to produce metal oxides.

The correct answer is oxygen.

Fill in the blank:

…… and ....... metals have very low melting points.

1962509_1823006_ans_6d88be3853294114b25f1e196ba2b0f4.jpg

The names of some metals are given below:
Tungsten, Gold, Sodium, Copper, Iron, Magnesium

Answer the following questions by selecting the appropriate ones from the list.
$$\bullet$$ Which metal with high malleability is used for making ornaments?
$$\bullet$$ Which of these metals reacts with cold water?
$$\bullet$$ Which of these is a hard metal but corrodes easily?

$$\bullet$$ Gold metal with high malleability is used for making ornaments.
$$\bullet$$ Sodium reacts with cold water.
$$\bullet$$ Iron is a hard metal but corrodes easily.

$$(X_i)$$	$$(Y_i)$$	$$(Z_i)$$
Constantan	$$Cu, Al$$	Measuring tapes
Brass	$$Fe, Cr, Ni$$	Domestic utensils
Rolled gold	$$Pb, Sn, Sb$$	Common articles
Invar	$$Cu, Ni$$	Soldering
Stainless steel	$$Pb, Sn$$	Airships
Solder	$$Al , Mg$$	Printing types
Type metal	$$Fe, Ni$$	Artificial jewellery
Magnalium	$$Cu, Zn$$	Electrical resistances

Metal	Use	Property
Gold	$$\bullet$$
Copper	$$\bullet$$
Aluminium	$$\bullet$$
Zinc	$$\bullet$$
Iron	$$\bullet$$

Use	Property
To make utensils	________
To make aluminium foil	________
To making farming tools	________
To make electric wire	________
To make bells	________

Materials Metals And Non Metals - Class 8 Chemistry - Extra Questions