Density of Hot and Cold Air

Q.

Hot air is less dense than cold air.

1. True

2. False

Q.

Why Ventilators are must for a house even though there are windows. Explain?

Q. Which of the following is correct when warm air rises up at a place?

1. The surrounding cold air flows away from that place.
2. A low pressure region is created at that place.
3. The surrounding air flows into that place.
4. A high pressure region is created at that place.

Q. What happens to air when it is heated?

1. Contracts only
2. Expands only
3. Neither expands nor contracts
4. Both expands and contracts

Q. While constructing a house, where do we construct ventilators; why?

Q.

What makes a balloon get inflated when air is filled in it?

Q.

Why are ventilators provided at a height in a room?

Q. Air expands on heating and occupies more space.

1. True
2. False

Q. Ventilators are provided near ceilings in the rooms of our houses because:
1. Hot air is lighter than cool air.
2. Hot air rises up and cool air settles down.
3. Hot air is heavier than cool air.

1. 2 and 3 only
2. 1 and 3 only
3. 1, 2 and 3
4. 1 and 2 only

Q. The warm air is denser than the cold air.

1. True
2. False

Q. What are the utilities of ventilators present near the ceiling of a room?

1. They act as vents for cold air to enter the room.
2. They can be used to store food grains and other things.
3. They act as vents for hot air to pass out of the room.
4. We use them to escape in case of an emergency.

Q. Pressure is measured at two positions in an open field as shown.
Which of the following statements is correct?

1. Wind will flow from right to left.
2. Wind will flow from left to right.
3. Wind will flow in an upward direction.
4. There will be no wind flow.

Q. Why does the air in an air-conditioned room go out when the door is opened?

Q. A change in air pressure is observed with the change in temperature.

1. False
2. True

Q. Explain why the balloon attached to the bottle mouth inflates when the bottle is kept in the hot water as shown below.

Q. What happens to air when it is heated?

1. Contracts only
2. Expands only
3. Neither expands nor contracts
4. Both expands and contracts

Q. Warm air is ______ than cold air.

1. lighter
2. denser
3. heavier
4. humid

Q. Warm air is lighter than cool air.

1. True
2. False

Q. Atmospheric pressure _________ with ________ in altitude.

1. increases, increase
2. decreases, decrease
3. decreases, increase
4. remains constant, increase

Q.

When hot air rises up, the number of air particles in the region:

1. Decreases

2. Increases

3. Remains the same

4. Becomes zero

Q. When warm air rises at a place, what happens to the air pressure there?

1. Air pressure decreases
2. Cannot be determined
3. Air pressure remains unaffected
4. Air pressure increases