Secondary School (English Medium) (5 to 8) इयत्ता ७ - CBSE Question Bank Solutions for Science

State whether the following statement is true or false:

When a candle burns, both physical and chemical changes take place.

Melting of wax is a change where a solid changes to liquid state. Give one more such change which you observe in your surroundings

Iron benches kept in lawns and gardens get____________. It is a _________ change because a new _________ is formed.

Classify the following processes into physical or chemical changes:

1. Beating of aluminium metal to make aluminium foil.
2. Digestion of food.
3. Cutting of a log of wood into pieces.
4. Burning of crackers.

Write word equations for two chemical reactions with the help of materials given in the box.

Give two examples for the following case:

Chemical changes

Give an example of a chemical reaction for the following situation:

A change in colour is observed

If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.

Can you change rust back into iron by some simple method?

If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust.

Do you think formation of rust from iron is a chemical change?

A student took a solution of copper sulphate in a beaker and put a clean iron nail into it and left it for about an hour.

What changes do you expect?

A student took a solution of copper sulphate in a beaker and put a clean iron nail into it and left it for about an hour.

Are these changes chemical in nature?

A student took a solution of copper sulphate in a beaker and put a clean iron nail into it and left it for about an hour.

Write a word equation for the chemical change, if any.

Out of the given definitions, which is the most appropriate definition of climate?

Which of the following briefly describes the desert climate?

Paheli went to a wildlife sanctuary where she saw dense vegetation of trees, shrubs, herbs and also a variety of animals like monkeys, birds, elephants, snakes, frogs, etc. The most likely location of this sanctuary is in the –

Read the following environmental conditions of tropical rain forests.

1. Hot and humid climate
2. Unequal lengths of day and night
3. Abundant rain fall
4. Abundant light and moisture

Identify the conditions from the above list that are responsible for the presence of large number of plants and animals in tropical rain forests.

State whether the following statement is True or False. Correct the false statement.

Penguins stick together to fight the cold polar climate.

Why is it difficult to predict the weather of a place while it is easy to predict its climate?

Given below is a list of climatic conditions and some examples of animals. Read them carefully and place the items in the relevant columns as shown.

Penguin, Gorilla, Monkey, Reindeer, Assam, Greenland, Sun does not rise for six months, Hot and humid climate, Days and nights are almost equal in length throughout the year, Winter temperature around –37°C, Western Ghats

Figure shows a child blowing air with a straw near the opening of another straw which has its other end in a soft drink bottle. It was observed that the level of the soft drink in the straw rises up as soon as air is blown over its open end. Which one of the following best explains the reason for rise in level of the drink?