MCQExams
0:0:1
CBSE
JEE
NTSE
NEET
Practice
Homework
×
CBSE Questions for Class 7 Chemistry Physical And Chemical Changes Quiz 2 - MCQExams.com
CBSE
Class 7 Chemistry
Physical And Chemical Changes
Quiz 2
Which of them is not the characteristics of a physical change?
Report Question
0%
Change in the physical properties
0%
New substances are formed
0%
Reversible reaction
0%
Original substance can be reverted back
Explanation
1) A physical change is temporary and is usually reversible.
2) No new substances are formed during a physical change.
3) There is no change in mass of the substance during a physical change.
4) There is no net absorption or release of energy during a physical change.
A change in the physical state can be brought about:
Report Question
0%
only when energy is given to the system
0%
only when energy is taken out from the system
0%
when energy is either given to, or taken out from the system
0%
without any energy change
Explanation
A change in a physical state can be brought about when energy is either given to or taken out from the system.
For example, if we give energy or heat to ice, it will convert to liquid water similarly if we took out the energy (or cool it) from the water it will convert back to ice.
Therefore, the correct option is ($$C$$).
Melting of butter is a physical change.
State whether the statement is true or false
Report Question
0%
True
0%
False
0%
Either
0%
Neither
Explanation
No chemical
bonds are broken or formed in
melting butter
, so it is not a
chemical change
. The
melting
process is only a
physical change
, the
change
of state from solid to liquid.
Glowing of an electric bulb is a ______ change.
Report Question
0%
physical
0%
chemical
0%
both physical and chemical changes
0%
none of these
Explanation
When electricity is passed through the bulb (tungsten ) the electrons in the atoms get excited and release the energy as light in terms of photons. So no chemical reaction is taking place. It is a physical reaction.
Which of the following is a physical change ?
Report Question
0%
solubility in water
0%
combustibility
0%
oxidation
0%
reaction with water
Explanation
1. A physical change is reversible, a chemical change is not. For example, the freezing of water would be a physical change because it can be reversed, whereas the burning of wood is a chemical change, you can't 'unburn' it.
2. A physical change is a change in which no new substance is formed; a chemical change results in the formation of one or more new substances. Again, consider the previous examples: Freezing water into ice just results in water molecules which are 'stuck' together, it's still $$H_2O$$. Whereas burning wood results in ash, carbon dioxide etc.
So, solubility just changes phase and it is a physical change.
Which of these will cause a chemical change to occur ?
Report Question
0%
Grinding of wheat into flour
0%
Lighting of gas stove
0%
Evaporation of water from a lake
0%
Ringing of an electric bell
Explanation
In gas burning, in a stove, the hydrocarbons from the fuel of the stove burns to form Carbon dioxide and Water vapour. As new substances are formed this is a chemical change.
Option B is correct.
Which of the following reaction involve change of state?
Report Question
0%
Burning of magnesium in air
0%
Decomposition of water
0%
Iron nail with copper sulphate solution in water
0%
Heating of copper sulphate
Explanation
(A) Burning of magnesium in air
When magnesium is burnt, it reacts with the oxygen present in air to form magnesium oxide.
$$2Mg+O_2 \rightarrow 2MgO$$
The magnesium ribbon burns with a bright white light. After it burns, it forms a white powder of magnesium oxide.
(C) Iron nail with copper
sulphate
solution in water
When an iron nail is dipped in copper sulphate solution the blue color of the copper sulphate solution changes to green. As iron is more reactive than copper, it displaces copper from copper sulphate solution.
$$Fe+ CuSO_4 \rightarrow FeSO_4 + Cu$$
This is a displacement reaction.
(D) Heating of copper
sulphate
When copper sulphate crystals are heated, the blue color of the crystal is lost and it changes to white. When copper sulphate is heated, it loose water molecule. It becomes anhydrous copper sulphate.
$$CuSO_4.5H_2O \xrightarrow {\triangle} CuSO_4 + 5H_2O$$
Which among the following is not a physical change ?
Report Question
0%
Melting of solids to liquids
0%
Vaporisation of liquids to gasses
0%
Liquefaction of gasses to liquids
0%
Decay of matter
Explanation
Melting, vapourisation and liquification all are pure physical changes where the chemical composition of the material does not change. But during the decay of matter, there occurs a permanent chemical change catalysed by living organism. So the correct option is D
Report Question
0%
Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
0%
Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
0%
Assertion is correct but Reason is incorrect
0%
Both Assertion and Reason are incorrect
Explanation
Burning of the candle is both physical and chemical change. Burning of the candle melts the wax and hence physical state of wax has changed from solid to liquid.
Again the wax combines with the atmospheric oxygen and changes to carbon dioxide, heat and light.
Thus both the changes are accompanied by the burning of the candle.
Chemical changes are _____ .
Report Question
0%
temporary, reversible and a new substance is produced
0%
always accompanied by exchange of light
0%
permanent, irreversible and a new substance is produced
0%
never accompanied by exchange of light and heat energy
Explanation
Chemical changes take place on the molecular level. A chemical change produces a new substance. It is a permanent and irreversible change.
Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan.
Give reason to show that the following is a chemical change:
Burning of magnesium in air.
Report Question
0%
New substance is formed with different properties.
0%
No new substance is formed.
0%
The reaction is reversible.
0%
None of these
Explanation
A chemical change is one in which the identity of the substance is altered to produce one or more new substances. Burning of anything is a chemical change as new substances are formed in the process. The reaction is irreversible.
A. Hammering of a red hot iron rod to make a flat sheet.
B. Formation of ice by cooling of water.
C. Rising up of water vapours from sea to make clouds.
D. Heating of charcoal in air to high temperature till it begins to glow.
Report Question
0%
A, B and C
0%
B, C and D
0%
C, D and A
0%
D, A and B
Explanation
Physical changes are those type of changes affecting the form of a chemical substance, but not it's chemical composition.
A. Hammering of a red hot iron rod does not change the composition of that rod.
B. Formation of ice by cooling water is a classic example of physical change. Here the chemical composition of water molecule remains intact during the process.
C. Rising up of water vapours to form cloud is also a physical change.
D. Heating of charcoal in the air to high temperature till it begins to flow is a chemical change where the chemical composition of charcoal changes.
So the correct option is A.
The reaction given below is a:
$${Copper \ sulphate + Iron\rightarrow Iron \ sulphate +Copper}$$
Report Question
0%
chemical change
0%
physical change
0%
both A and B
0%
we cannot determined
Explanation
Since the reaction involves the formation of two new substances iron sulphate and copper, it is a chemical change.
So, the correct option is A.
Neutralization is:
Report Question
0%
a physical change
0%
a chemical change
0%
sometimes physical and sometimes chemical change
0%
neither a physical nor chemical change
Explanation
Neutralization is a chemical change since it involves the formation of new compounds, salt and water.
Example:
$$HCl +NaOH\rightarrow NaCl+H_2O$$
Some pieces of chalk were taken and mixed with water. In this change, how many new substances are formed?
Report Question
0%
1
0%
2
0%
3
0%
No new substance is formed
Explanation
No new substances are formed. The chalk when mixed with water, no chemical reaction occurs. The chalk disperses in water which can be separated by filtration.
Two changes are stated below:
(i) A piece of magnesium gives of bright flames when burnt.
(ii) A piece of iron glows red when heated strongly.
Which of these is a chemical change?
Report Question
0%
i only
0%
ii only
0%
Both i and ii
0%
None of the above
Explanation
i) When magnesium is burnt, it reacts with the air and gives bright flames and this change cannot be reversed. It is a chemical change. The new product form is Magnesium oxide.
ii) When iron heated strongly it turns red. When heating is stopped it cools and gets back to its original form. So this is a physical change.
Burning of wood is a _____ change.
Report Question
0%
Reversible
0%
Physical
0%
Irreversible
0%
All of these
Explanation
Answer should be irreversible. When wood is burnt a new substance is formed which cannot be reversed.
Adding salt to water makes it salty.
Which of the following is true regarding this change?
Report Question
0%
It is a chemical change because a new substance is formed
0%
It is a physical change because the original substances can be recovered
0%
It is a chemical change because there is exchange of heat
0%
It is a physical change because there is a slight change in colour
Explanation
Adding salt to water makes it salty. This is a physical change because the original substances can be recovered by evaporation. In a chemical change, substances cannot be recovered.
The change given below is an example of :
$$\text{Hydrogen + Oxygen}$$ $$\longrightarrow$$ $$\text {Water}$$
Report Question
0%
Physical change
0%
Chemical change
0%
Both A and B
0%
Neutralization reaction
Explanation
Hydrogen and oxygen combine together to form water is a chemical change. When a new substance is formed the change is called a chemical change.
Two changes are stated below:
(i.) A piece of magnesium gives of bright flames when burned.
(ii). A piece of iron glows red when heated strongly.
Which of these is a physical change?
Report Question
0%
Only i
0%
Only ii
0%
Both i and ii
0%
Neither i nor ii
Explanation
When magnesium is burnt, it reacts with oxygen and gives bright flames. This is a chemical change and cannot be reversed.
When iron is heated strongly, it turns red. When heating is stopped, it cools and gets backs to its original form. So this is a physical change. Hence option B is correct.
Which of the following is true for ash, which is obtained by burning wood in the presence of oxygen?
Report Question
0%
The properties of ash will be similar to wood
0%
The properties of ash will be similar to oxygen
0%
The properties of ash will be different from both wood and oxygen
0%
None of the above
Explanation
The burning of wood in the presence of oxygen produces ash. In this example, wood and oxygen undergo a chemical change to produce ash. The properties of ash are very different from wood or oxygen. So, options A, B, and D are incorrect and, option C is correct.
Which of the following is NOT a chemical change?
Report Question
0%
Digestion of food
0%
Precipitation of rain and snow
0%
Rusting of iron
0%
Burning of paper
Explanation
Precipitation
is any product of the condensation of atmospheric water vapour
that falls under gravity.
The main forms of precipitation include drizzle
, rain
, sleet, and
snow
.
Precipitation occurs when a portion of the atmosphere becomes saturated with water vapour so that the water condenses and "precipitates". Here the water vapour in the air is changing from one form to another.
So precipitation of snow and rain is not a chemical change. In all the other options, a new substance is formed and the main substances cannot be reversed. So, they are chemical changes.
For rusting of iron to take place _______ are required.
Report Question
0%
$${O_2}$$ and $${CO_2}$$
0%
$${H_2O}$$ and $${N_2}$$
0%
$${H_2O}$$ and $${O_2}$$
0%
$${H_2O}$$ and $${H_2}$$
Explanation
Rusting of iron consists of the formation of hydrated oxide, $$Fe_2O_3.xH_2O$$. It is an electrochemical process that requires the presence of water, oxygen, and an electrolyte.
Adding sodium chloride to water is a:
Report Question
0%
physical change
0%
chemical change
0%
irreversible change
0%
None of these
Explanation
Physical changes are changes in the physical properties of substances. No new substances are formed in these changes.
The addition of sodium chloride to water does not result in the formation of any new substance, hence it is a physical change. Also, sodium chloride can be reversed back to its original state by simple evaporation of water. Therefore, it is a reversible change.
So, the correct option is A.
Classify the changes involved in the following process as physical or chemical changes.
Dissolving sugar in water.
Report Question
0%
Physical
0%
Chemical
0%
Both A and B possible according to condition
0%
Can not be predicted
Explanation
Dissolving sugar in water in water is usually considered to be a physical change, in this process there is no new chemical species form.
Which of the following change is not a chemical change?
Report Question
0%
Boiling of water
0%
Boiling of egg
0%
Burning of paper
0%
Burning of cloth
Explanation
The boiling of water is not a chemical change. If it boils for more time it changes to vapour state which is a physical change.
Whereas boiling of egg, burning of paper and cloth involves both physical and chemical change. The burning of paper and cloth forms ash.
The formation of water is a reversible change. Identify the chemical
equation
of the formation of water.
Report Question
0%
$${H_2+2O_2\rightarrow 2 H_2O}$$
0%
$${2H_2+O_2\rightarrow H_2O}$$
0%
$${H_2+O_2\rightarrow H_2O}$$
0%
$${2H_2+O_2\rightarrow 2 H_2O}$$
Explanation
For a balanced equation, the number of atoms of each element must be the same on both sides of the equation. The number of atoms of hydrogen on the left-hand side of the equation is 4 which is the same on the right-hand side of the equation. The number of atoms of oxygen on the left-hand side of the equation is 2 which is the same on the right-hand side of the equation.
Beating silver to make silver foil is _______change.
Report Question
0%
Physical
0%
Chemical
0%
Biochemical
0%
None of these
Explosion of a fire work (such as a cracker)
Report Question
0%
Chemical
0%
Physical
0%
Both A and B possible according to condition
0%
Can not be predicted
Explanation
An explosion of a cracker is a chemical change because the explosive reactants are transformed into gaseous products along with heat, light, and sound which cannot be reversed.
The gas you use in kitchen is called liquefied petroleum gas (LPG). In the cylinder, it exists as a liquid. When it comes out of the cylinder, it becomes a gas (process A), then it burns (process B). Choose the correct statement.
Report Question
0%
Process A is a chemical change
0%
Process B. is a chemical change
0%
Both processes A and B are chemical changes
0%
None of these processes is a chemical change
Explanation
LPG gas is also known as propane or butane are mixtures of hydrocarbon gases. LPG is heavier than air and it is flammable when ignition source is present.
0:0:1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
0
Answered
0
Not Answered
0
Not Visited
Correct : 0
Incorrect : 0
Report Question
×
What's an issue?
Question is wrong
Answer is wrong
Other Reason
Want to elaborate a bit more? (optional)
Practice Class 7 Chemistry Quiz Questions and Answers
<
>
Support mcqexams.com by disabling your adblocker.
×
Please disable the adBlock and continue.
Thank you.
Reload page
