Motion and Time — Science STD 7 — Question

Why is digestion important for animals?

Paheli observed that most of the fish in the pond of her village were gradually dying. She also observed that the wastes of a factory in their village are flowing into the pond which probably caused the fish to die.
(i) Explain why the fish were dying?
(ii) If the factory waste is acidic in nature, how can it be neutralised?

List two differences between conductors and insulators.

Explain why: Calamine solution is applied on the skin when an ant bites.

Paheli does not have a night lamp in her room. She covered the bulb of her room with a towel in the night to get dim light. Has she taken the right step? Give one reason to justify your answer.

Explain how water seeps through the surface of the Earth and gets stored as groundwater.

(a) Name the watch that have an electric circuit with one or more cells.
(b) Name the ancient time measuring device.

The image formed by a lens is always virtual, erect and smaller in size for an object kept at different positions in front of it. Identify the nature of the lens.

Imagine a world without light. How would this affect our understanding of time and space?