ICSE ICSE Class 7 - CISCE Question Bank Solutions

Change is the law of nature and occurs in our everyday life, at all times and in all places.
Differentiate between the following change with a suitable example.

Natural and man-made change.

Differentiate between a physical change and a chemical change with reference to – Nature of change is temporary and reversible or permanent and irreversible.

Differentiate between a physical change and a chemical change with reference to – Formation of products.

Differentiate between a physical change and a chemical change with reference to – Energy change taking place during the respective change.

Give three reasons why melting of wax, is considered a physical change while burning of a candle, a chemical change.

State the observations seen, when milk in a dish is kept aside for a few hours or more. Is the change which occurs – a physical change or a chemical change. Give reasons.

State what is meant by the term – interconversion of matter. Is interconversion of matter a physical change or a chemical change.

Ice kept in a beaker, slowly melts and turns into water. The water in the beaker on solidification is freezing turns back to ice. Give four reasons why the change from ice to water and water back to ice is considered a physical change.

Explain the term – ‘sublimation’. Is sublimation of naphthalene – a physical or a chemical change. Give reasons.

Ammonium chloride is also a sublimable solid. Give a reason why the sublimation of ammonium chloride involves a physical and a chemical change.

State why addition of sodium chloride to water is considered a physical change, while addition of dilute sulphuric acid to zinc is considered a chemical change.

Photosynthesis is a natural process by which green plants manufacture food in the presence of sunlight.

State the conclusions which can be drawn, to represent photosynthesis as a physical or a chemical change.

Give reasons why – separation of mixtures e.g. iron from a mixture of iron and sulphur is a physical change, but heating a mixture of iron and sulphur is considered a chemical change.

Give a reason why oiling or greasing is done on the exposed moving iron parts of machinery and not preferred on heavy stationary iron parts.

Fill in the blank with the appropriate word of the statement given below:

Germination of seeds is considered a __________ change.

Fill in the blank with the appropriate word of the statement  given below:

If a change is permanent and irreversible it is considered a _________ change.

Fill in the blanks with the appropriate words of the statement  given below:

Heating a piece of iron is considered a __________ change while heating a piece of coal [carbon] is considered a ___________ change.

State why galvanization, tinning and chromeplating are used as three different processes for coating specific articles for prevention of rusting.

State whether the following statement is true or false. If false write the correct statement.

Melting of butter and wax are examples of chemical changes.

State whether the following statement is true or false. If false write the correct statement.

Melting of ice is an exothermic, irreversible chemical change.