Science 7 · Unit 5: Properties of materials · Cambridge Lower Secondary Science Stage 7

Questions

1. 📖 This question is about a text that students read in the app.

   1. Marcus wrote "lemon juice, yellow, pH 4, weakly alkaline". What is his mistake?

   • The colour. Lemon juice is purple.
   • The conclusion. pH 4 is weakly acidic, not weakly alkaline.
   • The pH. Lemon juice is pH 11.
   • There is no mistake.
   Check

2. 📖 This question is about a text that students read in the app.

   2. Marcus wrote "soap solution, blue/green, pH 8, weakly alkaline". Is this row correct?

   • Yes
   • No
   Check

3. 📖 This question is about a text that students read in the app.

   3. Marcus wrote "water, green, pH 5, neutral". What is his mistake?

   • Neutral water is pH 7, not pH 5.
   • Water is strongly alkaline.
   • Water is red.
   • There is no mistake.
   Check

4. 📖 This question is about a text that students read in the app.

   4. Marcus wrote "hydrochloric acid, blue, pH 2, strongly acid". What colour should it be?

   • red
   • blue
   • purple
   • green
   Check

5. 📖 This question is about a text that students read in the app.

   5. Marcus wrote "sodium hydroxide, blue/purple, pH 11, strongly alkaline". Is this row correct?

   • Yes
   • No
   Check

6. 6. What colour does universal indicator turn in a neutral liquid such as pure water?

   • purple
   • yellow
   • green
   • red
   Check

7. 7. What is the pH of a neutral liquid?

   • 1
   • 14
   • 5
   • 7
   Check

8. 8. Look at the pH scale. A liquid turns universal indicator the colour of pH 1. What is it?

   • strongly alkaline
   • weakly acidic
   • neutral
   • strongly acidic
   Check

9. 9. Look at the pH scale. A liquid turns universal indicator the colour of pH 6. What is it?

   • weakly acidic
   • neutral
   • strongly acidic
   • weakly alkaline
   Check

10. 10. Look at the pH scale. A liquid turns universal indicator the colour of pH 13. What is it?

    • weakly alkaline
    • neutral
    • strongly alkaline
    • strongly acidic
    Check

11. 11. What does an indicator do?

    • It makes a solution neutral.
    • It makes acids into alkalis.
    • It measures temperature.
    • It changes colour to show whether something is an acid or an alkali.
    Check

12. 12. How could you make your own indicator from red cabbage?

    • Freeze it and weigh it.
    • Boil it in salt water and add sand.
    • Crush it in ethanol with a pestle and mortar, then filter.
    • Leave it in the sun for a week.
    Check

13. 13. How could you check that your home-made indicator works?

    • Smell it.
    • Heat it until it boils.
    • Add it to a known acid and a known alkali, and see that it turns different colours.
    • Add it to pure water only.
    Check

14. 14. Why can't a home-made indicator show whether coffee or cola is acidic?

    • Their dark colour hides the indicator's colour change.
    • Coffee and cola are too hot.
    • Indicators only work on solids.
    • Coffee and cola are neutral.
    Check

15. 📖 This question is about a text that students read in the app.

    15. Use the table. What colour is phenolphthalein at pH 10?

    • yellow
    • red
    • colourless
    • pink
    Check

16. 📖 This question is about a text that students read in the app.

    16. Use the table. What colour is methyl orange at pH 1?

    • red
    • colourless
    • yellow
    • pink
    Check

17. 📖 This question is about a text that students read in the app.

    17. Use the table. A liquid makes phenolphthalein stay colourless and methyl orange turn red. What is its pH most likely to be?

    • pH 1
    • pH 7
    • pH 10
    • pH 13
    Check

18. 18. Why is universal indicator more useful than litmus?

    • It shows how strong an acid or alkali is, not just which it is.
    • It is cheaper.
    • It only works on acids.
    • It is always green.
    Check