Secondary School (English Medium) (5 to 8) Class 7 - CBSE Question Bank Solutions

State whether the following statement is True or False. If false, correct them.

The rearing of silkworms for obtaining silk is called silviculture.

Some words related to silk are jumbled up. Write them in their correct form.

TURECULRISE

Some words related to silk are jumbled up. Write them in their correct form.

WILSMORK

Some words related to silk are jumbled up. Write them in their correct form.

BELMURRY

Some words related to silk are jumbled up. Write them in their correct form.

RINGLEE

Steps for the production of silk are given below in a jumbled order. Arrange them in their proper sequence.

1. Eggs are warmed to a suitable temperature for the larvae to hatch from eggs.
2. Fibres are taken out from the cocoon.
3. After 25 to 30 days, the caterpillars stop eating and start spinning cocoons.
4. The larvae/caterpillars or silkworms are kept in clean trays along with freshly chopped mulberry leaves.
5. Female silk moths lay eggs.
6. Cocoons are kept under the sun or boiled in water.

Complete the paragraph related to the life history of silk moth by filling in the blanks.

The ___(a)___ silk moth lays ___(b)___, from which hatch ___(c)___ called ___(d)___ or ___(e)___. They grow in size and when the caterpillar is ready to enter the next stage of its life history called ___(f)___, it first weaves a covering to hold itself, which is known as ___(g)___.

Paheli went to the market to buy sarees for her mother. She took out a thread from the edge of the two sarees shown by the shopkeeper and burnt them. One thread burnt with a smell of burning hair and the other burnt with the smell of burning paper. Which thread is from a pure cotton saree and which one from a pure silk saree? Give reason for your answer.

Describe the life history of the silk moth with the help of figures of various stages.

Boojho has three thermometers as shown in the following figure. He wants to measure the temperature of his body and that of boiling water. Which thermometer (s) should he choose?

Four arrangements to measure temperature of ice in beaker with laboratory thermometer are shown in the following figure (a, b, c and d). Which one of them shows the correct arrangement for accurate measurement of temperature?

Figure (a–d) shows a student reading a doctor’s thermometer. Which of the figure indicates the correct method of reading temperature?

A laboratory thermometer A is kept 7 cm away on the side of the flame while a similar thermometer B is kept 7 cm above the flame of a candle as shown in the following figure.

Which of the thermometers, A or B, will show a greater rise in temperature? Give reason for your answer.

In a mercury thermometer, the level of mercury rises when its bulb comes in contact with a hot object. What is the reason for this rise in the level of mercury?

You may have noticed that a few sharp jerks are given to a clinical thermometer before using it. Why is it done so?

Why is it advised not to hold the thermometer by its bulb while reading it?

Products of a neutralisation reaction are always ______.

Neutralisation reaction is a ______.

Look at the given reaction.

Hydrochloric acid + Sodium hydroxide (base) → Sodium chloride (salt) + Water

Sodium chloride formed in this reaction remains in solution form. Can we get solid sodium chloride from this solution? Suggest a method (if any).

Form a sentence using the following words – baking soda, ant bite, moist, effect, neutralised, rubbing.