MEDIUM
7th West Bengal Board
IMPORTANT
Earn 100

Fill up the following table.

Change of phase Name of the phase Latent heat absorbed/released Name of the latent heat
Solid to liquid Melting/Fusion   Latent heat of fusion
Liquid to solid Solidification Released  
Liquid to vapour Evaporation Absorbed  
Vapour to liquid Condensation    

 

Important Questions on Physical Environment

EASY
7th West Bengal Board
IMPORTANT
Environment and Science Class 7>Chapter 1 - Physical Environment>Exercise 10

During the daytime, we can see everything- bed, almirah, chair, table, etc. When all the sources of the light are put off after the sunset and moonlight or streetlight can not enter the room, we can not see anything in the room. But at that time if a firefly manages to enter the room, we feel no trouble in observing the firefly. Now think and say:

How could you see the firefly?

EASY
7th West Bengal Board
IMPORTANT
Environment and Science Class 7>Chapter 1 - Physical Environment>Exercise 10
Why could you not see the other things in the room in the dark which you could see in the daytime?
EASY
7th West Bengal Board
IMPORTANT
Environment and Science Class 7>Chapter 1 - Physical Environment>Exercise 10
If you want to see things at night, what do you require?
EASY
7th West Bengal Board
IMPORTANT
Environment and Science Class 7>Chapter 1 - Physical Environment>Exercise 11

Fill in the blanks in the following table. Put the Yes in the appropriate place.

Objects Luminous Non-luminous
1. Kerosene lamp    
2. Pen    
3. Shirt button    
4. Burning candle    
5. Firefly    
6. Umbrella    
7. Star    
8. Spectacles    
9. Sun    
10. Moon    
EASY
7th West Bengal Board
IMPORTANT
Environment and Science Class 7>Chapter 1 - Physical Environment>Exercise 12
Can light pass through water? Can you see the bottom of a bucket filled with water from its side?
EASY
7th West Bengal Board
IMPORTANT
Environment and Science Class 7>Chapter 1 - Physical Environment>Exercise 13
Can you see the flame of the candle through that bent pipe? Why does it happen so?
EASY
7th West Bengal Board
IMPORTANT
Environment and Science Class 7>Chapter 1 - Physical Environment>Exercise 13

Question Image

In the picture, does the light from the flame of the candle fail to reach your eyes?

EASY
7th West Bengal Board
IMPORTANT
Environment and Science Class 7>Chapter 1 - Physical Environment>Exercise 13

Question Image

Why does light fail to reach your eyes? Is there any obstacle on the path of light? Why does light get obstructed?