Test: Physical & Chemical Changes- 1


15 Questions MCQ Test Science Class 7 | Test: Physical & Chemical Changes- 1


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QUESTION: 1

Melting of ice is a

Solution:

Melting of ice is a physical change because no new substance is formed.

QUESTION: 2

Which of these is the smallest particle?

Solution:

An atom is the smallest particle that forms molecules.

QUESTION: 3

Formation of a compound is

Solution:

When two or more atom combine together in fixed ratio new compound is formed so, it is a chemical change.

QUESTION: 4

Which of the following is a reversible change?

Solution:

Melting of ice is a reversible change while burning of matchstick, changing of milk into curd and germination of seed is chemical change.

QUESTION: 5

Crystals of copper sulphate are prepared by the method of

Solution:

Crystals of copper sulphate are prepared by the method of crystallization. It is an example of physical change.

So option D is correct answer. 

QUESTION: 6

In chemical change

Solution:

In chemical changes, molecules of substance rearrange to form a new substance with different property.

QUESTION: 7

Which of the following is an example of physical change?

Solution:

Boiling of water is a physical change:
Boiling of water produce water vapors. Chemically the water and water vapors composed of H2O molecules. Here the change in physical state occurred. During this conversion The liquid is changed in to gas. On cooling these water vapors condensed into water. Hence it is a reversible reaction.

QUESTION: 8

Sea water is a

Solution:

Sea water is a mixture because sea water contain a number of salts dissolved in it.

QUESTION: 9

Which is a method to prevent rust?

Solution:

Galvanization or galvanizing is the process of applying a protective zinc coating to steel or iron, to prevent rusting. 

QUESTION: 10

Which among the following is an example of a Chemical Change? 

Solution:

Rusting of iron is a chemical change because it happens due to a chemical reaction between iron and air in presence of moisture.

QUESTION: 11

The reaction of H2 gas with oxygen gas to form water is an example of

Solution:

The electrons are transferred from Hydrogen to Oxygen , hence Oxygen is reduced and electrons are accepted by Oxygen from Hydrogen , hence Hydrogen is oxidised . Now , both oxidation and reduction are going together , therefore it is  a Redox (Reduction- Oxidation reaction) reaction 

QUESTION: 12

The process of obtaining salt by the evaporation of sea water is called 

Solution:

Crystallisation is the  process of obtaining salt by the evaporation of sea water. 

QUESTION: 13

Brown color of the apple after cutting is 

Solution:

When an apple is cut (or bruised), oxygen is introduced into the injured plant tissue. The oxygen  present in cells, polyphenol oxidase (PPO) enzymes in the chloroplasts rapidly oxidize phenolic compounds naturally present in the apple tissues to o-quinones, colorless precursors to brown-colored secondary products. So it's a chemical change.

QUESTION: 14

When magnesium is burnt heat and light are produced. The burning of magnesium is a :

Solution:

Burning of magnesium ribbon in air is an example of chemical change. This is because when we burn magnesium ribbon in presence of oxygen it forms magnesium oxide . From magnesium oxide we cannot get back it's original state.

QUESTION: 15

 One or more new substances are formed due to

Solution:

 One or more new substances are formed due to chemical change.

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