Chemical Change

Q.

The burning of a candle is a chemical change whereas the melting of a candle is a physical change. Why?

Q.

What are immiscible liquids? Give an example.

Q.

What are the different types of combination reactions? Give an example of each

Q.

Give an example of a combination reaction between an element and a compound.

Q.

Conversion of milk into curd Is______?

1. A physical change

2. A chemical change

3. A physical property of milk

4. A chemical property of milk

Q. Define reversible and irreversible change.

Q.

Two methods by which rusting of iron can be prevented are _________ and _________.

Q.

Changes in which new substances are formed are called _________ changes.

Q.

Which of the following methods are used to prevent rusting of iron?

1. evaporation

2. galvanization

3. heating

4. crystallization

Q.

When some salt is mixed with water, the salt appears to disappear. What has happened to the salt?

1. Salt has broken down into chlorine and sodium

2. Salt has evaporated.

3. Salt has dissolved.

4. Salt has disappeared.

Q.

Question 11
The gas we use in the kitchen is called liquefied petroleum gas (LPG). In the cylinder, it exists as a liquid. When it comes out from the cylinder it becomes a gas (Change–A) then it burns (Change–B). The following statements pertain to these changes. Choose the correct one.
Which of the processes is a chemical change?
(i) Process – A is a chemical change.
(ii) Process – B is a chemical change.
(iii) Both processes A and B are chemical changes.
(iv) None of these processes is a chemical change.

Q. The dissolution of sugar in water is a:

1. physical change
2. chemical change
3. irreversible change
4. reversible change

Q.

Which of the following is a Ferroelectric compound?

1. ${\mathrm{Pb}}_2{\mathrm{O}}_3$

2. ${\mathrm{K}}_4\left[\mathrm{Fe}{\left(\mathrm{Cn}\right)}_6\right]$

3. ${\mathrm{BaTiO}}_3$

4. None of these.

Q.

Question 3

A chemical change may involve
(a) change in colour only
(b) change in temperature only
(c) evolution of gas only
(d) All of the these

Q.

Corrosion of metals is an example of a chemical change.

1. True

2. False

Q. Curdling of milk is a chemical change.give reason.

Q.

Give a few examples of undesirable changes.

Q.

What happens when Borax is heated strongly?

Q.

Rusting of iron is both chemical and physical change . Why?

Q.

Name the method used for the separation of sodium chloride from its solution in water.

Q.

Chemical changes are mostly irreversible.

1. True

2. False

Q. Chopping of vegetables is a physical change.

1. True
2. False

Q.

Why is lightning a candle an exothermic reaction?

Q.

Give scientific reasons for the fermentation is a chemical change.

Q.

A student took a solution of Copper sulfate in a beaker and put a clean Iron nail into it and left it for about an hour.

(a) What changes do you expect?

(b) Are these changes chemical in nature?

(c) Write a word equation for the chemical change, if any.

Q. Formation of manure from leaves is a:

1. physical change
2. chemical change
3. periodic change
4. reversible change

Q. Blending a smoothie, for example, involves two physical changes: the change in shape of each fruit and the mixing together of many different pieces of fruit. But the outcome of this blending is not at all the same as the original fruit. So can you justify why it cannot be termed as a chemical change? [3 MARKS]

Q.

By giving a reason state why chemical change takes place in the following case:

When grapes are fermented to make wines

Q.

Differentiate between the followinhg -

Galvanization and Tinning

Q.

Classify the changes involved in the following processes as physical or chemical changes: (a) Photosynthesis (b) Dissolving sugar in water (c) Burning of coal (d) Melting of wax (e) Beating aluminium to make aluminium foil (f) Digestion of food