The Ever-Evolving World of Science — Science STD 7 — Question

What is sludge? Explain, how it is treated?

One morning as Paheli strolled in her garden she noticed many small plants, which were not there a week ago. She wondered, where they had come from as nobody had planted them there. Explain the reason for the growth of these plants.

Explain why factory waste should be neutralised before disposing it into the water bodies.

How do short circuits occur?

Write the reaction that takes place when iron nails are dipped in copper sulphate solution.

What is the site of production of bile? Which component of the food does it digest?

Batteries used in tractors, trucks and inverters are also made from cells. Then why it is called a battery?

At a camp site there are tents of two shades. One made with black fabric and the other with white fabric. Which one will you prefer for resting on a hot summer afternoon? Give reason for your choice. Would you like to prefer the same tent during winter?

Why is digestion important for animals?

State the SI unit of speed and time.