Diversity In Living Organisms — Science STD 9 — Question

When is the work done said to be negative?

What volume of ethyl alcohol and water must be mixed together to prepare 250ml of 60% volume by volume solution of alcohol in water.

Explain why, naphthalene balls kept in stored clothes in our homes disappear over a period of time.

A boy weighing 40kg carries a box weighing 20kg to the top of a building 15m high in 25 seconds. Calculate the power. (g = 10m/s²)

A student placed a gas jar containing air in the upside down position over a gas jar full of red-brown bromine vapours. He observed that the red brown colour spread upwards into the jar containing air. Based on this observation, the student concluded that it is only the bromine vapour which moves up and diffuses into air in the upper jar, the air from the upper jar does not move down by diffusion into the lower jar containing bromine vapours. Do you agree with this conclusion of the student? Give reason for your answer.

Define ‘molecular mass’ of a substance.

Distinguish between the following pairs in one or two sentences for each:

Bone and cartilage.

Write two differences between isobars and isotopes.