Physical Change and Chemical Change

Q. Among the following, the substance expected to have the highest ignition temperature is

1. Kerosene
2. Petrol
3. Coal
4. Alcohol

Q.

Lean air-fuel mixture is required for

1. Idling

2. Cruising

3. Starting

4. Acceleration

Q.

Wood, petrol, kerosene oil and LPG are _______substances.

Q. Methane on complete combustion gives a _______ flame.

1. blue
2. red
3. yellow
4. green

Q. Which of the following is not necessary for combustion to take place?

1. Oxygen
2. Fuel
3. Carbon dioxide
4. Heat

Q.

1 mole of Hydrocarbon requires a maximum volume of oxygen for complete combustion under the same condition. Identify the hydrocarbon.

1. ${\mathrm{CH}}_4$

2. ${\mathrm{C}}_2{\mathrm{H}}_6$

3. ${\mathrm{C}}_3{\mathrm{H}}_6$

4. ${\mathrm{C}}_4{\mathrm{H}}_8$

Q.

Give reason for the following:

Carbon dioxide gas is used in fire extinguishers.

Q. Why water is poured to extinguish fire on a burning substance ?

Q.

Why is it dangerous to burn methane in an insufficient supply of air?

Q. Pieces of iron taken in a spatula is burnt, but it fails to burn. Hence it can be concluded that iron is a/an:

1. non-combustible substance
2. explosive
3. hydrocarbon
4. combustible substance

Q.

Which type of fire extinguisher cannot be used to put out fires caused due to electrical appliances or equipment.

Q. When water is poured over burning wood, the fire goes off. This is because _________.

1. Temperature of wood decreases
2. Temperature of water goes up
3. Molecules of water reacts with oxygen present in the flame
4. Flame vaporizes

Q. Give reason- Water is not used to control fires involving electrical equipment.

Q. Water cannot be used to extinguish ________.

1. household fires
2. electrical fires
3. forest fires
4. burning paper

Q. Which of the following is a good conductor of electricity?

1. Phosphorus
2. Copper
3. Hydrogen
4. Carbon