Sources of Energy — Science STD 10 — Question

Name two ores of zinc. Write the names of the chemical compounds present in them and give their chemical formulae.

Why is LPG considered a better fuel than coal?

What is meant by biodiversity? List two advantages of conserving forests and wild life.

To find-the image-distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image of the screen.

1. In which direction - towards or away from the lens, does he move the screen to focus the object?
2. What happens to the size of the image - does it increase or decrease?
3. What happen when he moves the object very close to the lens?

Write equations for the reactions of:

1. Iron with steam.
2. Calcium and potassium with water.

1. E is the gene for brown eye colour and and e is the gene for blue eye colour. which gene is:

1. Recessive.
2. Dominant.

2. Both father and mother have the genes Ee in their cells. What colour are their eyes?
3. Which combination of genes in the zygote will produce children with blue eyes?
4. Which combination of genes in the zygote will produce children with brown eyes?

What will be the formula and electron dot structure of cyclopentane?

Why must we conserve our forests? List two factors responsible for causing deforestation.

Water in deep sea is blue in colour. Why?

What can best method be used for the safe disposal of hospital wastes?