1. 1
   A waiter places an ice cube into a glass of lemonade on a hot day, and after a few minutes the ice cube has completely melted into the drink.

   (a)

   What type of change has occurred?

   [1 mark]

   • AA chemical change, because a new substance has formed
   • BA physical change, because no new substance has formed
   • CA chemical change, because energy has been transferred
   • DNeither a physical nor a chemical change

   (b)

   Which observation would show that the melting of the ice cube is easily reversible, supporting the conclusion that it is a physical change?

   [1 mark]

   • AThe melted water could be refrozen into ice again
   • BThe melted water changes colour permanently
   • CA gas is released with a strong smell
   • DThe melted water cannot be turned back into ice

   (c)

   Explain, in terms of particles, why melting the ice cube is classified as a physical change rather than a chemical change.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A homeowner notices that an old iron gate left outside has developed a flaky, orange-brown coating over several months of exposure to rain and air.

   (a)

   What type of change has produced this coating?

   [1 mark]

   • AA physical change, as the iron has simply changed shape
   • BNo change has taken place, only the appearance is different
   • CA physical change, as the iron has changed state
   • DA chemical change, as a new substance, hydrated iron(III) oxide, has formed

   (b)

   Which piece of evidence would best support the conclusion that rusting is a chemical change rather than a physical one?

   [1 mark]

   • AThe rust can be scraped off and reshaped back into solid iron
   • BThe gate becomes cold to the touch
   • CThe rust has completely different properties, such as colour and strength, from the original iron
   • DThe gate can be melted and reshaped into a new gate

   (c)

   State two differences in general between physical changes and chemical changes, using the melting ice and the rusting gate as examples.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A chef adds sodium hydrogencarbonate (baking soda) to a bowl containing vinegar, and immediately sees vigorous bubbling and hears a fizzing sound.

   (a)

   Explain why this observation suggests a chemical change has taken place, rather than a physical change.

   [3 marks]

   (b)

   The chef also dissolves some ordinary table salt into a separate bowl of warm water, and later evaporates the water to leave the salt crystals behind. Compare this process with the baking soda and vinegar reaction, explaining which is a physical change and which is a chemical change, and how each could be confirmed experimentally.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A metal recycling plant crushes and melts down scrap aluminium cans to cast new aluminium ingots, while a separate part of the same plant burns waste plastic and cardboard packaging in an incinerator to generate electricity.

   (a)

   Explain which of these two processes is a physical change and which is a chemical change, justifying your answer with reference to the substances involved.

   [6 marks]

   (b)

   The plant manager wants to reduce the environmental impact of the incineration process. Using your knowledge of chemical changes, discuss why burning the waste plastic and cardboard could have negative environmental consequences, and suggest how the physical process of recycling the aluminium avoids these issues.

   [6 marks]

   Total for question 4: 12 marks

End of questions