Explain thermal expansion with suitable examples.

When a window is accidentally left open on a winter night, will you feel uncomfortable because the cold is getting in, or because the heat is escaping from the room?

If you heat a circular disk with a hole, what change do you expect in the diameter of the hole? Remember that the effect of heating increases the separation between any pair of particles.

What is the source of electricity? Explain the various power stations in India?

Write short notes on conductors and insulators.

When a candle is lit the following changes are observed.
a. Wax melts.
b. Candle keeps burning.
c. The size of the candle decreases.
d. The molten wax solidifies
e. Which of the changes can be reversed? Justify your answer.

Why is atmosphere essential for life on earth?

Tabulate any five cell organelles and their function.

Label the diagram given below to show the four main parts of the urinary system and answer the following questions.

A. Which organ removes extra salts and water from the blood?
B. Where is the urine stored?
C. What is the tube through which urine is excreted out of the body?
D. What are the tubes that transfer urine from the kidneys to the urinary bladder called?

Why do we hiccup and cough sometimes when we swallow food?