Science 7 · Unit 8: Changes to materials · Cambridge Lower Secondary Science Stage 7

Questions

1. 1. Why does indigestion medicine help when your stomach makes too much acid?

   • The medicine is an acid, so it adds more acid.
   • The medicine makes your stomach colder.
   • The medicine turns the acid into a gas.
   • The medicine is an alkali, so it neutralises the acid.
   Check

2. 2. How does Marcus know when the acid is neutralised?

   • The universal indicator turns green.
   • The acid turns red.
   • The beaker gets cold.
   • The powder disappears.
   Check

3. 3. Marcus counts spatulas of indigestion powder needed to neutralise acid. What is the best heading for the second column of his table?

   • Number of spatulas needed to turn the indicator green
   • Colour of the powder
   • Temperature of the room
   • Name of the medicine shop
   Check

4. 4. Arun used 50 cm³ of acid for powders A and C, but 25 cm³ for powder B. Is it a fair test?

   • No, the volume of acid changed.
   • Yes, all the beakers had indicator.
   • No, he used the wrong indicator.
   • Yes, he tested three powders.
   Check

5. 5. Sofia used sulfuric acid for powder A, and hydrochloric acid for powders B and C. Is it a fair test?

   • No, the type of acid changed.
   • Yes, the volumes were the same.
   Check

6. 6. Zara added indicator to two beakers but not to the third. Is it a fair test?

   • No, she cannot see when the third beaker is neutral.
   • Yes, the acid was the same in all three.
   Check

7. 7. What is a variable?

   • something that can change in an experiment
   • a piece of equipment
   • the result of an experiment
   • a type of chemical
   Check

8. 8. The scientist adds sodium hydroxide to lake water to neutralise it. What must she keep the same for a fair test?

   • the volume of sodium hydroxide added
   • nothing, it does not matter
   • the lake the water comes from
   • the volume of lake water and the concentration of the sodium hydroxide
   Check

9. 9. Why does the scientist test each lake sample three times?

   • to use up the sodium hydroxide
   • to make the lake less acidic
   • to check the results are repeatable and to find a mean
   • because one test is never correct
   Check

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

    10. Which lake is the most acidic?

    • lake B
    • lake C
    • lake A
    • they are all the same
    Check

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

    11. Which lake is the least acidic?

    • they are all the same
    • lake C
    • lake A
    • lake B
    Check

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

    12. Check the mean for lake A. What is (4 + 6 + 5) ÷ 3?

    • 15
    • 5
    • 6
    • 4
    Check

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

    13. What pH did antacid B reach after 2 g?

    • pH 2
    • pH 7
    • pH 5
    • pH 4
    Check

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

    14. Which variables did Arun and Zara keep the same?

    • the type of antacid
    • the pH after each addition
    • nothing
    • the volume and pH of the acid, and the mass of antacid added each time
    Check

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

    15. Which antacids had the biggest effect on pH?

    • A and C
    • A only
    • C and E
    • B and D
    Check

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

    16. Which antacid raised the pH most quickly?

    • C
    • A
    • B
    • E
    Check

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

    17. Which antacid had the least effect on pH?

    • C
    • E
    • A
    • D
    Check

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

    18. What pH would you expect after adding 2.5 g of antacid B?

    • pH 7
    • pH 6
    • pH 5
    • pH 8
    Check

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

    19. Estimate the mass of antacid A needed to reach pH 5.5.

    • 2.5 g
    • 5.5 g
    • 4.5 g
    • 3.5 g
    Check

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

    20. Antacids that work very quickly make a lot of gas quickly. Which would make the best antacid?

    • one that reaches pH 7 but works more slowly, like D
    • the fastest one, B
    • C, because it hardly changes the pH
    • none of them
    Check