Metals and Non-Metals — Science STD 10 — Question

Why does the sun appear red at sunrise?

Does the incident and emergent ray coincide in the process of refraction through glass slab? Give reason.

Give one example of an exothermic reaction and one of an endothermic reaction.

“To discard the household waste we should have two separate dust-bins, one for the biodegradable waste and the other for the non-biodegradable waste.” Justify this statement suggesting the proper way of disposal of these wastes.

To avoid accidental fires, some metals are kept immersed in kerosene oil. Why?

Where are genes located in an organism?

What is a tendril? Name the two types of tendrils. What does a tendril do in response to the touch of a support ? What is this phenomenon known as?

What happens when a cold and concentrated solution of sodium chloride reacts with ammonia and carbon dioxide? Write the chemical equation of the reaction which takes place.

Explain the mechanism of gaseous exchange between tissues and blood.

How could the person change his eating habits to lessen chances of suffering from tooth decay?