Question 4:
Match the following:
(i) |
Land breeze blows during |
(a) |
summer |
(ii) |
Sea breeze blows during |
(b) |
winter |
(iii) |
Dark coloured clothes are preferred during |
(c) |
day |
(iv) |
Light coloured clothes are preferred during |
(d) |
night |
Answer:
(i) |
Land breeze blows during |
(d) |
night |
(ii) |
Sea breeze blows during |
(c) |
day |
(iii) |
Dark coloured clothes are preferred during |
(b) |
winter |
(iv) |
Light coloured clothes are preferred during |
(a) |
summer |
Question 5:
Discuss why wearing more layers of clothing during winters keeps us warmer than wearing just one thick piece of clothing.
Answer:
During winters, we prefer wearing more layers of clothing than just one thick piece of clothing because air gets trapped in between the various clothing layers. Being a poor conductor of heat, air prevents heat loss from our body. Hence, layers of clothing keep us warmer than a single layer.
Question 6:
Look at Figure. Mark where the heat is being transferred by conduction, by convection and by radiation.
(i) Transfer of heat from burner to pan is by radiation.Answer:
(ii) Transfer of heat from pan to water is by conduction.
(iii) Transfer of heat within water is by convection.
Question 7:
In places of hot climate it is advised that the outer walls of houses be painted white. Explain.
Answer:
In places of hot climate, it is advised to paint the outer walls of houses as white because a light colour such as white reflects back most of the heat that falls on it. Hence, a light colour tends to keep the house cool.
Question 8:
One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be
(a) 80°C (b) more than 50°C but less than 80°C
(c) 20°C (d) between 30°C and 50°C
Answer:
(d)
The temperature of the mixture will be between 30°C and 50°C.