The Fundamental Unit of Life — Science STD 9 — Question

Define valence of an element. Find the valency of chlorine and magnesium (At. No. of chlorine = 17, magnesium = 12).

Which contains more heat, 1kg of water at 100°C or 1kg of steam at 100°C? Give reason for your answer.

There are two types of forces X and Y. The forces belonging to type X can produce motion in a stationary object but cannot change the shape of the object. On the other hand, forces belonging to type Y cannot produce motion in a stationary object but can change the shape of the object. What is the general name of the forces such as (a) X, and (b) Y?

An object weighs 10 N when measured on the surface of the earth. What would be its weight when measured on the surface of the moon?

Why is the density of solids mostly higher than that of liquids?

Give the reason for the rising of balloons in air.

If a 50W bulb is lighted for 3h daily. Give the energy consumed in 30 days.

Is the uniform circular motion accelerated? Give reasons for your answer.