Friction — Science STD 8 — Question

The part of P and Q are present only in plant cells, and they are not present in animal cells. The part P contains a green pigment called R whereas part Q is made of a tough material S. The part P takes part in the food making process whereas part Q gives shape and support to the plant cell.

1. What is (i) P, and (ii) Q?
2. What is (i) R, and (ii) S?

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?

Give an example to show that friction depends on the force with which the two surfaces are pressed together.

An Ameoba cell can change its shape and a white blood cell in human blood can also changing its shapes. What is the difference between an Amoeba cell and a white blood cell?

Compare the Chemical Properties of Metals and Non-metals in tabular form.

Describe menstrual cycle. What is the duration of menstruation cycle in women?

Where are chromosomes found in a cell? State their function.

What are metals? Name five metals.

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

Write two changes that happen during puberty to: (a) both boys and girls (b) boys only (c) girls only.