CBSE Questions for Class 7 Chemistry Physical And Chemical Changes Quiz 6 - MCQExams.com

Crystallization takes place by the process of :
  • evaporation
  • condensation
  • sublimation
  • liquefication
Vacuum desiccator is used  _____ 
  • for drying crystals
  • for purifying crystals
  • for separation of crystals
  • for the process of crystallisation
A synthetic indicator phenolphthalein gives ________ colour in basic solution.
  • Red
  • Blue
  • Pink
  • Colorless
Solvent dissolve large amount of solute at________.
  • room temperature
  • boiling temperature
  • freezing temperature
  • less than room temperature but more than freezing temperature
Which of the following is the most common solvent used for crystallization?
  • Organic solvent - benzene
  • Water
  • A salt solution
  • Dilute solution of sulphuric acid
All of the following processes involve a separation of either a mixture into its components or a compound into elements. For each, decide whether the physical process or chemical reaction is required.
a. Sodium metal is obtained from the substance Sodium chloride.
b. Iron filings are separated from the sand by using a magnet,
c. Sugar crystals are separated from sugar syrup by the evaporation of water.
d. Fine crystals of Silver chloride are separated from a suspension of the crystals in water.
e. Copper is produced when Zinc metal is placed in a solution of Copper (II) sulphate, a compound.
  • a, b, c, d, e - physical
  • a, d, b, c, e - chemical
  • b, c, d - physical ; a, e - chemical
  • e a, b - physical ; c, d - chemical
The process of forming large crystals of pure substances from their solutions is known as __________.
  • evaporation
  • purification
  • condensation
  • crystallisation
Which of the following is a physical change?
  • Burning of coal
  • Photosynthesis
  • Dissolving sugar in water
  • Digestion of food
Crystallisation is an example of ____________.
  • physical change
  • biological change
  • chemical change
  • fundamental change
Select the option that correctly gives the examples of physical and chemical changes.
  • Physical change- Tearing of paper, Chemical change- Breaking of glass
  • Physical change- Burning of paper, Chemical change- Cooking of food
  • Physical change- Rusting of iron, Chemical change- Melting of butter
  • Physical change- Formation of ice, Chemical change- Burning of wood
Which of the above represent a chemical change?
799096_746396c0f25644f2914f9351cb99ef20.JPG
  • (i) and (ii)
  • (ii) and (iii)
  • (i) and (iii)
  • All of these
Study the given Venn diagram carefully. Identify 1, 2 and 3.

810824_5a6454f19c8249f7a8fe931b833f2785.jpg
  • 1- Melting of ice, 2- Rusting of iron, 3- Cutting a log of wood
  • 1- Glowing of bulb, 2- Bursting of tyre, 3- Crystallisation
  • 1- Stitching of garments, 2- Burning of a match stick, 3- Burning of a candle
  • 1- Melting of ice, 2-Decompositon of sugar, 3- Sublimation
Salt can be obtained by ___________ of sea water.
  • sublimation
  • cooling
  • evaporation
  • heating
Which of the following do not represent that a chemical change is taking place?
I. A gas is produced.
II. Precipitate is formed.
III. State of a substance changes
IV. A new odour is produced
V. Shape of a substance changes
  • I and V only
  • I and IV only
  • II, III and V only
  • III and V only
Cutting of a log of wood is a chemical change.
  • True
  • False
A substance appears coloured because:
  • it absorbs light at a specific wavelength in the visible part and reflects rest of the wavelengths
  • ligands absorb different wavelengths of light which give colour to the complex
  • it absorbs white light and shows different colours at different wavelength
  • it is diamagnetic in nature
Iron rod turns red on heating. What kind of change is this?
  • Physical change
  • Periodic change
  • Physical and chemical change
  • Chemical change
Which is an example of a chemical change?
  • The melting of ice
  • The burning of wood
  • The grindig of salt crystals powder
  • The evaporation of water from a sea
Paheli's mother made concentrated sugar syrup by dissolving sugar in hot water. On cooling, crystals of sugar got separated. This indicates:
  • Physical change that can be reversed
  • Chemical change that can be reversed
  • Physical change that cannot be reversed
  • Chemical change that cannot be reversed
Stretching of rubber band is not a physical change.
  • True
  • False
The diagram shows experiments involving the rusting of iron.
The following results were suggested.
1 In tube $$P$$, the iron nails rust.
2 In tube $$Q$$, the iron nails do not rust.
3 In tube $$R$$, the iron nails do not rust.
Which results are correct?

1646800_939a62ad69994d41b29b65c48209d1dd.png
  • $$1$$ and $$2$$ only
  • $$1$$ and $$3$$ only
  • $$2$$ and $$3$$ only
  • $$1, 2$$ and $$3$$
Which of the following is a chemical change?
  • Twinkling of stars
  • Cooking of vegetables
  • Cutting of fruits
  • Boiling of water
A chemical change may involve-
  • Change in colour only
  • Change in temperature only
  • Evolution of gas only
  • All of the above
Chemical formula of rust is
  • $$ FeO $$
  • $$ Fe_3O_4 $$
  • $$ Fe_2O_3.x H_2 O $$
  • $$ FeO .xH_2 O $$
A student is given a mixture of barium sulfate, copper(II) sulfate and water.
The table shows information about barium sulfate and copper(II) sulfate.

SubstanceSolubility in waterState at room temperature
Barium sulfateInsolubleSolid
Copper(II) sulfateSolubleSolid

How does the student obtain copper(II) sulfate crystals from the mixture?
  • Crystallisation followed by distillation
  • Crystallisation followed by filtration
  • Distillation followed by crystallisation
  • Filtration followed by crystallisation
Which of the following are chemical changes?
(i) Decaying of wood
(ii) Burning of wood
(iii) Sawing of wood
(iv) Hammering of a nail into a piece of wood
  • (i) and (ii)
  • (ii) and (iii)
  • (iii) and (iv)
  • (i) and (iv)
Choose the most appropriate answer:
     
Physical changes are:
  • permanent
  • periodic
  • temporary
  • irreversible
Choose the most appropriate answer:  
  
Chemical changes involve;
  • change in shape
  • change in size
  • change in molecular composition
  • none of these
Write 'true' or 'false' for the given statement. Rewrite the false statement correctly:                 
Dissolving of solute in a solvent and rusting of iron are both physical changes.
  • True
  • False
Chemical change involve 
  • change in shape
  • change in size
  • change in composition of atoms.
  • none of these
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