Change in State

Q. (a) Air is a matter because it has ……….and………… and it can be ………..

Q.

The burning of a candle is accompanied by the change of state.

1. True

2. False

Q.

Combustion is said to take place when a substance burns in ______________ with the release of large amount of heat energy.

1. Air

2. Oxygen

3. Any (A) or (B)

4. None of the above.

Q. Question 4
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

Q.

The high diffusibility of gases is due to

1. high intermolecular forces of attraction

2. high KE of molecules

3. restricted translatory motion in the upward direction

4. all the above

Q.

Sublimation is an example of physical change.

1. True
2. False

Q.

Complete and balance the following equation and also state the type of reaction that is taking place:

$\mathrm{Fe}+{\mathrm{Cl}}_2\stackrel{}{\to }\mathrm{\_\_\_\_\_\_}$

Q. Ice changes into water on .

1. cooling
2. freezing
3. heating

Q.

Explain in brief the involvement of energy in - physical & Chemical changes.

Q.

There are different types of chemical reactions depending upon the ______ and the __________under different ____________.

Q.

What is an exothermic reaction? Explain with two examples.

Q. A decomposition reaction is generally represented as .

1. $A+B\to \mathrm{AB}$
2. $\mathrm{AB}\to A+B$
3. $\mathrm{AB}+C\to \mathrm{AC}+B$

Q. Which of these suggest that a chemical reaction may be occurring?

1. Change of colour
2. Change of state
3. Change in temperature
4. Emission of gas

Q.

When wax is burnt (in the form of a wax candle), then water and carbon dioxide are formed. This shows the "change in state" characteristic of reactions.

1. True

2. False

Q.

The process by which a solid changes into a liquid is called?

1. Freezing

2. Melting

3. Condensation

4. Boiling

Q.

When hydrogen gas is burnt in oxygen gas, it results in the formation of

1. hydrogen

2. oxygen

3. water

4. nothing

Q. Hina dipped a glass rod in $\text{conc. HCl}$ and observed faint fumes. These fumes became dense when she dipped the same glass rod in ${\text{NH}}_3$ gas. The possible reason for Hina's observation is:

1. the sublimation of ${\text{NH}}_4\text{Cl}$ which is formed when $\text{HCl}$ reacts with ${\text{NH}}_3$.
2. the condensation of ${\text{NH}}_4\text{Cl}$ which is formed when $\text{HCl}$ reacts with ${\text{NH}}_3$.
3. the sublimation of ${\text{NH}}_4\text{OH}$ which is formed when $\text{HCl}$ reacts with ${\text{NH}}_3$.
4. the evaporation of ${\text{NH}}_4\text{OH}$ which is formed when $\text{HCl}$ reacts with ${\text{NH}}_3$.

Q. Hina dipped a glass rod in $\text{conc. HCl}$ and observed faint fumes. These fumes became dense when she dipped the same glass rod in ${\text{NH}}_3$ gas. The possible reason for Hina's observation is:

1. the sublimation of ${\text{NH}}_4\text{Cl}$ which is formed when $\text{HCl}$ reacts with ${\text{NH}}_3$.
2. the condensation of ${\text{NH}}_4\text{Cl}$ which is formed when $\text{HCl}$ reacts with ${\text{NH}}_3$.
3. the sublimation of ${\text{NH}}_4\text{OH}$ which is formed when $\text{HCl}$ reacts with ${\text{NH}}_3$.
4. the evaporation of ${\text{NH}}_4\text{OH}$ which is formed when $\text{HCl}$ reacts with ${\text{NH}}_3$.

Q. Decomposition of water into hydrogen and oxygen involves absorption of energy.

1. \N
2. \N

Q. The conversion of ${\text{CaCO}}_3$ into $\text{CaO}$ is an example of ____________ reaction.

1. decomposition
2. combination
3. double displacement
4. displacement

Q. write down the reactions involving the physical change and chemical change. give atleast 5 examples

Q. Which of the following are not decomposition reactions?

1. ${\text{CaCO}}_3\text{(s)}{}^{\underrightarrow{\text{heat}}}\text{CaO(s)}+{\text{CO}}_2\text{(g)}$
2. ${\text{2KClO}}_3\text{(s)}{}^{\underrightarrow{\text{heat}}}\text{2KCl(s)}+{\text{3O}}_2\text{(g)}$
3. $\text{Zn(s)}+\text{2HCl(aq)}\to {\text{ZnCl}}_2\text{(aq)}+{\text{H}}_2\text{(g)}$
4. ${\text{H}}_2\text{(g)}+{\text{Cl}}_2\text{(g)}\to \text{2HCl(aq)}$