Structure of the Atom — Science STD 9 — Question

What are the functiors of phloem?

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.

Name the process which causes a long term withdrawal of carbon from carbon cycle?

Which chemical compound does make cork impermeable for liquid and gases?

A boy throws a rubber ball vertically upwards. What type of work, positive or negative, is done:

1. By the force applied by the boy?
2. By the gravitational force of earth?

What will happen in a cell if its nucleus is removed? Give reasons in support of your answer.

Name any two ways by which microorganisms can find entry into human body.

What is meant by the quality (or timbre) of sound? On what factor does the quality (or timbre) of a sound depend?

What is meant by the term ‘buoyancy’?