Chemical effects of electric current — Science STD 8 — Question

What are the various measures which can be taken to conserve forests and wildlife?

Which of the following will cause regular reflection of light and which diffuse reflection of light?

1. Polished wooden table.
2. Chalk powder.
3. Cardboard.
4. Mirror.
5. Paper.
6. Marble floor with water spread over it.

Which plastic is used:

1. For making uniforms of fire-men fire resistant?
2. For giving non-stick coating on frying pans?
3. For making handles of frying pans?
4. For making insulation (covering) of electric wires?
5. For making electric switches?
6. For making flexible water bottles?

When a human female reaches a certain age, then vaginal bleeding occurs for a few days after regular intervals of time:

1. What is this process known as (i) In scientific terms, and (ii) In everyday language?
2. What is the human female said to have attained at this stage?
3. What does the onset of this process in human female signify?
4. At what particular event in the life of a human female this process stops temporarily but starts again?
5. What name is given to the event when this process stops permanently?

A woman is in her reproductive phase of life. Even when the sperms are available at the time of release of a mature ovum by her ovary, fertilization does not take place. Due to this, the woman is unable to bear a baby.

1. What is the most likely defect in the reproductive system of this woman?
2. Name the technique by which this woman can also have a baby?

What are the functions of the following organs?

1. Heart.
2. Brain.
3. Roots.
4. Leaves.

What kind of friction comes into play:

1. When a block of wood kept on table moves slowly?
2. When a block of wood kept on table just tends to move (or slip)?
3. When a block of wood kept on cylindrical iron rods moves?

Explain why, chloroplasts are found only in plant cells.

How does a lightning conductor protect a tall building? Name the scientist who invented the lightning conductor.

Who is responsible for the sex of the unborn child: father or mother? Why?