Physical and Chemical Changes quiz

Which is a chemical change?

Magnesium burns with a:

The gas that turns lime water milky is:

Rusting of iron requires:

Coating iron with zinc is called:

When an iron nail is placed in copper sulphate solution, the solution turns:

The solution of magnesium oxide in water is:

Crystallisation is a:

Which is a physical change?

The brown deposit on the iron nail in copper sulphate solution is:

Why is burning of a candle both a physical and a chemical change? (2 marks)

Why is the ozone layer important? Is its formation a chemical change? (2 marks)

Why should iron gates be painted regularly? (2 marks)

What happens when carbon dioxide is passed through lime water? (2 marks)

Why is stainless steel used in kitchens? (2 marks)

Is dissolving sugar in water a physical change? Give a reason. (2 marks)

Name two chemical changes that occur in our body. (2 marks)

Why does a cut apple turn brown? (2 marks)

Why is the formation of curd a chemical change? (2 marks)

Give two examples of physical changes that are not easily reversible. (2 marks)

In an experiment, 5 iron nails were kept in moist air, 5 in dry air and 5 in boiled water with oil. After a week 5, 0 and 0 nails rusted respectively. What fraction of all nails rusted? What do the results show? (3 marks)

Classify and count: melting of butter, rusting, cooking rice, boiling water, burning petrol, folding cloth, digestion of food, stretching a rubber band, ripening of mango. How many are chemical changes? (3 marks)

India spends crores of rupees every year replacing rusted iron. If a factory replaces 120 tonnes of rusted iron yearly and galvanisation reduces this by 75 percent, how many tonnes will it replace after galvanising? (3 marks)

A student dissolves 20 g of copper sulphate in 100 mL of hot water and obtains 12 g of crystals after cooling. What percentage of copper sulphate was recovered as crystals? Is it a physical change? (3 marks)

Write the word equations for three reactions in this chapter and state one observation for each. (3 marks)

Read the passage and answer the questions. Paheli's bicycle left out in the rain for a month had reddish-brown flakes on it, while her brother's bicycle kept under a shed was fine. (i) What are the flakes? (ii) Why did her bicycle get them? (iii) Suggest two ways to protect it. (5 marks)

Read the passage and answer the questions. Boojho added a spoon of baking soda to vinegar in a test tube. He heard a hissing sound and saw bubbles. He passed the gas into lime water. (i) Name the gas. (ii) What happened to the lime water? (iii) Is this a physical or chemical change? (5 marks)

Read the passage and answer the questions. A teacher burnt a magnesium ribbon with tongs. The ash was mixed with water and tested with litmus. (i) What is the ash? (ii) What will happen to red litmus? (iii) Why should we not look directly at burning magnesium? (5 marks)

Read the passage and answer the questions. Ice cream melts on a hot day; when put back in the freezer, it freezes again but its shape changes. (i) Is melting a physical or chemical change? (ii) Why is it reversible? (iii) Was a new substance formed? (5 marks)

Read the passage and answer the questions. Iron bridges near the sea are painted every few years, while water pipes are coated with zinc. (i) Why do iron structures near the sea rust faster? (ii) What is coating with zinc called? (iii) How do paint and zinc prevent rusting? (5 marks)

Describe the activity of burning magnesium ribbon and testing the product. Write the word equations and draw the set-up. (6 marks)

Describe an experiment to show that both air and moisture are needed for rusting, with a labelled diagram of three test tubes. (6 marks)

Explain the crystallisation of copper sulphate with steps and a labelled diagram. Why is it called a physical change? (6 marks)

Distinguish between physical and chemical changes on five points with examples. (6 marks)

Describe the reaction of iron with copper sulphate solution. Write the word equation, draw before and after diagrams, and explain the colour changes. (6 marks)