Applications of physical and chemical changes Practice exercise 7

A hotel chef in Nairobi prefers to steam vegetables instead of boiling them before serving guests. Explain why steaming is more beneficial than boiling when preparing healthy meals.   (2 marks)

A hotel chef in Nairobi prefers to steam vegetables instead of boiling them before serving guests. Explain why steaming is more beneficial than boiling when preparing healthy meals.   (2 marks)

A hotel chef in Nairobi prefers to steam vegetables instead of boiling them before serving guests. Explain why steaming is more beneficial than boiling when preparing healthy meals.   (2 marks)

A hotel chef in Nairobi prefers to steam vegetables instead of boiling them before serving guests. Explain why steaming is more beneficial than boiling when preparing healthy meals.   (2 marks)

Jemimah notices that her clothes dry faster on a sunny, windy day than on a cold, calm day. Explain how changes in state help speed up this process.  (1 mark)

Jemimah notices that her clothes dry faster on a sunny, windy day than on a cold, calm day. Explain how changes in state help speed up this process.  (1 mark)

Jemimah notices that her clothes dry faster on a sunny, windy day than on a cold, calm day. Explain how changes in state help speed up this process.  (1 mark)

Jemimah notices that her clothes dry faster on a sunny, windy day than on a cold, calm day. Explain how changes in state help speed up this process.  (1 mark)

During a visit to a metal workshop, Grade 8 learners saw molten metal being poured into a mould. Why is it necessary to melt the metal first before shaping?   (1 mark)

During a visit to a metal workshop, Grade 8 learners saw molten metal being poured into a mould. Why is it necessary to melt the metal first before shaping?   (1 mark)

During a visit to a metal workshop, Grade 8 learners saw molten metal being poured into a mould. Why is it necessary to melt the metal first before shaping?   (1 mark)

During a visit to a metal workshop, Grade 8 learners saw molten metal being poured into a mould. Why is it necessary to melt the metal first before shaping?   (1 mark)

During a visit to a metal workshop, Grade 8 learners saw molten metal being poured into a mould. Why is it necessary to melt the metal first before shaping?   (1 mark)

In a plastic factory in Industrial Area, Nairobi, molten plastic is poured into moulds to create containers. Why must the plastic be heated first and cooled later?   (2 marks)

In a plastic factory in Industrial Area, Nairobi, molten plastic is poured into moulds to create containers. Why must the plastic be heated first and cooled later?   (2 marks)

In a plastic factory in Industrial Area, Nairobi, molten plastic is poured into moulds to create containers. Why must the plastic be heated first and cooled later?   (2 marks)

In a plastic factory in Industrial Area, Nairobi, molten plastic is poured into moulds to create containers. Why must the plastic be heated first and cooled later?   (2 marks)

At a juice-making factory in Thika, ice cubes are added to mango juice before bottling. The manager explains that this prevents fermentation. Explain how adding ice achieves this.  (1 mark)

At a juice-making factory in Thika, ice cubes are added to mango juice before bottling. The manager explains that this prevents fermentation. Explain how adding ice achieves this.  (1 mark)

At a juice-making factory in Thika, ice cubes are added to mango juice before bottling. The manager explains that this prevents fermentation. Explain how adding ice achieves this.  (1 mark)

At a juice-making factory in Thika, ice cubes are added to mango juice before bottling. The manager explains that this prevents fermentation. Explain how adding ice achieves this.  (1 mark)

During a science lesson in Nairobi School, two groups performed different experiments. One group boiled water to remove germs, while another group burned firewood to boil the water.Compare the changes that occurred in the boiling of water and in the burning of firewood. State the type of change in each case and explain how both changes are useful. (4 marks)

During a science lesson in Nairobi School, two groups performed different experiments. One group boiled water to remove germs, while another group burned firewood to boil the water.Compare the changes that occurred in the boiling of water and in the burning of firewood. State the type of change in each case and explain how both changes are useful. (4 marks)

In a village, some people burn plastic waste to get rid of it quickly. However, others complain about the smell and smoke. Explain the type of change that takes place when plastic burns.

In a village, some people burn plastic waste to get rid of it quickly. However, others complain about the smell and smoke. Explain the type of change that takes place when plastic burns.  (2 marks)

In a village, some people burn plastic waste to get rid of it quickly. However, others complain about the smell and smoke. Explain the type of change that takes place when plastic burns.  (2 marks)

A metal spoon was accidentally left inside a pot of salty soup overnight. The next day, brown patches were seen on the spoon. Explain what type of change occurred on the spoon and what caused it.  (2 marks)

A metal spoon was accidentally left inside a pot of salty soup overnight. The next day, brown patches were seen on the spoon. Explain what type of change occurred on the spoon and what caused it.  (2 marks)

A metal spoon was accidentally left inside a pot of salty soup overnight. The next day, brown patches were seen on the spoon. Explain what type of change occurred on the spoon and what caused it.  (2 marks)

The diagram below shows a freezer with fish placed inside. Ice crystals are forming around the fish. What kind of change is taking place in the fish during freezing, and how is this process useful in real life? (2 marks)

The diagram below shows a freezer with fish placed inside. Ice crystals are forming around the fish.What kind of change is taking place in the fish during freezing, and how is this process useful in real life? (2 marks)

The diagram below shows a freezer with fish placed inside. Ice crystals are forming around the fish.What kind of change is taking place in the fish during freezing, and how is this process useful in real life? (2 marks)

Dry leaves are shown in a pile with flames and smoke rising as they burn in the diagram below.  What type of change is taking place in the burning leaves, and how does this change affect the environment? (2 marks)

Dry leaves are shown in a pile with flames and smoke rising as they burn in the diagram below.  What type of change is taking place in the burning leaves, and how does this change affect the environment? (2 marks)

Dry leaves are shown in a pile with flames and smoke rising as they burn in the diagram below.   What type of change is taking place in the burning leaves, and how does this change affect the environment? (2 marks)

Dry leaves are shown in a pile with flames and smoke rising as they burn in the diagram below.   What type of change is taking place in the burning leaves, and how does this change affect the environment? (2 marks)