Blow Hot, Blow Cold - 1 Class 5 Worksheet EVS Chapter 15

Q1: Fill in the Blanks.

Answer: 
(i) Hot air is light and rises up.
(ii) Cold air is heavy and comes down.
(iii) Our breath is colder than hot tea and hence we blow air to cool tea.
(iv) We warm our hands in winter by blowing on them when they are cold.
(v) The air blown from our mouth is warm in cold winter.
(vi) The air we breathe out contains water vapour which turns into drops of water when comes in contact with a cold surface.
(vii) The woodcutter kept blowing into his hands while cutting the wood because to warm them.
(viii) A popcorn seller fans the burning coal to increase the air supply.
(ix) We use a stethoscope to listen to the sound of a heartbeat.
(x)Whenever the air flows downwards the paper snake will move in a clockwise direction.

Q2: Tick (✔) or Choose the Correct Answer.

(i) Suppose you are given hot khichdi to eat. How will cool down without blowing air from your mouth?
(a) By mixing cold water into it.
(b) By spreading it over the plate.
(c) By putting ice cubes into it.
(d) By spreading it over our palm.

Answer: (b) By spreading it over the plate.

(ii) Suppose you bang your head while playing and your forehead is swollen, a warmed handkerchief if put over it gives relief. Why is it so?
(a) Warm air kills germs on the injury.
(b) Handkerchief has medicine on it.
(c) Warm air soothes the skin giving relief.
(d) It is done to please children.

Answer: (c)Warm air soothes the skin giving relief.

Q3: Short Answer Questions

Answer: Because your breath is hotter than your skin.

(ii) Why do we blow at a burning fire?

Answer: Because air contains Oxygen which helps in the burning and a loud blow can extinguish
 the fire.

(iii) Name any two musical instruments we blow air into produce sound.

Answer: Flute and Been

(iv) Why do we blow on hot potatoes?

Answer: When we blow air on hot potatoes then water molecules escaped into the air because they got enough energy to change from liquid to a gaseous position.

Q4: Long Answer Questions

Answer: The air blown from the mouth is hot and the glass of the spectacles is comparatively colder. The hot air we breathe out contains water vapours which turn into tiny droplets of water when it comes in contact with the colder glass. This makes the glass moist and hazy.

(ii) Why do we see drops of water on your bathroom mirror, when you take a hot shower in winter?

Answer: During winter, the mirror in the bathroom absorbs the cold air from its environment and makes itself very cold. When a hot shower is taken, the water vapour from the hot water gets in contact with the cold surface of the mirror and condenses to form water droplets.