Changes Around Us quiz

Which of the following is a reversible change?

Which of the following is an irreversible change?

Metals generally expand on:

The change of water vapour into water is called:

The change of liquid into solid on cooling is called:

A blacksmith heats an iron rim before fitting it on a wooden wheel because heating makes the rim:

Which change takes place when we blow air into a balloon?

Ripening of a mango is:

When plaster of Paris is mixed with water, it:

Which is an example of change caused by heating that can be reversed?

Why is burning of a matchstick an irreversible change? (2 marks)

Give two examples of changes that are caused by mixing two substances. (2 marks)

Why are gaps left between the rails of a railway track? (2 marks)

Why does a cold glass bottle with a tight metal cap open more easily when the cap is dipped in hot water? (2 marks)

How is dissolving salt in water a reversible change? (2 marks)

Is the change of a seed into a plant reversible? Explain. (2 marks)

What happens to a piece of wax when heated and then cooled? (2 marks)

Why do clothes dry faster on a sunny day? (2 marks)

Give two examples of changes that are useful to us. (2 marks)

Give two examples of changes that are harmful to us. (2 marks)

Classify into reversible and irreversible and count each type: sharpening a pencil, melting ghee, burning incense stick, stretching a rubber band, boiling an egg, making chapati, drying of wet clothes, rusting of a gate, folding a cloth. (3 marks)

A metal rod is 100 cm long at 20 degrees C. It becomes 100.1 cm long at 100 degrees C. (i) By how much did it expand? (ii) What will happen to its length when it cools back to 20 degrees C? (iii) Name the change on cooling. (3 marks)

A bowl contained 200 g of ice. After melting, the water was weighed. (i) What should its mass be? (ii) If 20 g of water evaporated on heating, what mass of water is left? (iii) If the remaining water is frozen, what mass of ice is obtained? (3 marks)

Arrange these changes in the order they occur when a candle is lit and then put out: wax solidifies, wick catches fire, wax melts, wax vapour burns. Which of these changes are reversible and which are irreversible? (3 marks)

Electric wires between two poles are 50 m long in winter and become 50.05 m long in summer. Find the increase in length in centimetres. Will the wires sag more in summer or in winter? Explain. (3 marks)

Read the passage and answer the questions. Rahul's grandmother made curd by adding a spoonful of old curd to warm milk and keeping it overnight. In the morning the milk had changed into curd. Rahul asked whether the curd could be changed back into milk. (i) Is the formation of curd a reversible or irreversible change? (ii) Give a reason for your answer. (iii) Name one more change in the kitchen of the same type. (5 marks)

Read the passage and answer the questions. A blacksmith wanted to fix an iron rim on a wooden cart wheel. The rim was slightly smaller than the wheel. He heated the rim in a fire, placed it on the wheel and then poured cold water on it. (i) Why did he heat the rim? (ii) Why did he pour cold water on it? (iii) Name the property of metals used here. (5 marks)

Read the passage and answer the questions. During a science activity, students blew up balloons, stretched rubber bands, and also burnt small pieces of paper in a china dish under supervision. (i) Which of these changes are reversible? (ii) Which change is irreversible? (iii) What is the main difference between the two types? (5 marks)

Read the passage and answer the questions. Sona kept a glass of water in the freezer. After a few hours the water turned into ice. She took it out and kept it on the table, where it slowly became water again. (i) Name the change when water becomes ice. (ii) Name the change when ice becomes water. (iii) Is this change reversible? Explain. (5 marks)

Read the passage and answer the questions. A doctor set Ramu's broken arm using a bandage soaked in plaster of Paris paste. After some time the bandage became hard. After six weeks it had to be cut open to remove it. (i) What change occurs when plaster of Paris is mixed with water? (ii) Is the change reversible? (iii) Why did the bandage have to be cut instead of being softened again? (5 marks)

Describe an activity with a labelled diagram to show that metals expand on heating and contract on cooling. Give three examples from daily life where this property is used or must be taken care of. (6 marks)

Draw a flowchart of the water cycle showing evaporation and condensation. Explain why the changes of state of water are reversible, and give one example each of melting, freezing, evaporation and condensation. (6 marks)

Explain with examples the difference between reversible and irreversible changes. Draw a two-column list of six examples each. Explain why a burning candle shows both types of changes. (6 marks)

Draw a labelled diagram of a lit candle. Explain the changes taking place in the wax and the wick. Classify each change as reversible or irreversible and give reasons. (6 marks)

Explain how changes can be caused by heating, by mixing substances and by applying force. Give two examples of each and state whether each example is reversible or irreversible. Draw a labelled sketch for one example of each. (6 marks)