Science 9 · Unit 2: Properties of materials · Cambridge Lower Secondary Science Stage 9

Questions

1. 1. What is a lattice?

   • a single ion
   • a small group of atoms joined by covalent bonds
   • a gas made of molecules
   • a regular repeating arrangement of particles in a giant structure
   Check

2. 2. Match each structure with a property it usually has.

   • giant ionic lattice
   • simple covalent molecules
   • covalent macromolecule like diamond

   • very high melting point; very hard
   • low melting point; often a gas or liquid
   • high melting point; conducts when dissolved
   Check

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

   3. What type of bonding do you think Substance A has?

   • ionic, because it is a giant lattice of particles packed in a regular pattern
   • covalent, because it is made of separate small molecules
   • covalent, because its atoms share electrons in small molecules
   • no bonding, because the particles are just touching
   Check

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

   4. In Substance B, where are the strong forces?

   • between the separate molecules
   • There are no strong forces.
   • everywhere equally
   • inside each molecule, between the atoms
   Check

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

   5. Which substance has bonds where electrons are shared?

   • both A and B
   • neither A nor B
   • Substance B
   • Substance A
   Check

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

   6. Which substance has a lattice structure?

   • neither A nor B
   • Substance A
   • Substance B
   • both A and B
   Check

7. 7. A substance conducts electricity when it is dissolved in water, but not when it is solid. What type of bonding does it have?

   • ionic
   • covalent, in a macromolecule
   • none, it is an element
   • covalent, in simple molecules
   Check

8. 8. Diamond is a giant structure called a macromolecule. What type of bonding holds its atoms together?

   • ionic
   • covalent
   • weak forces between molecules
   • magnetic
   Check

9. 9. Which of these is a macromolecule, like diamond?

   • water
   • oxygen
   • graphite
   • sodium chloride
   Check

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

    10. Calcium chloride is an ionic compound that is solid at room temperature. What does that tell you?

    • Its boiling point is below room temperature.
    • It has no melting point.
    • Its melting and boiling points are high, well above room temperature.
    • Its melting point is below room temperature.
    Check

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

    11. Is Substance X a solid, liquid or gas at room temperature (about 20 °C)?

    • a solid
    • a liquid
    • a gas
    Check

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

    12. Which substances are solids at room temperature?

    • potassium chloride, magnesium oxide and bromine
    • potassium chloride, calcium chloride and magnesium oxide
    • calcium chloride, magnesium oxide and Substance Y
    • magnesium oxide only
    Check

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

    13. Which substances, other than Substance Y, have simple molecules with covalent bonds?

    • ammonia and magnesium oxide
    • bromine and potassium chloride
    • potassium chloride, calcium chloride and magnesium oxide
    • Substance X, ammonia and bromine
    Check

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

    14. Suggest what Substance Y is.

    • salt, because it is a solid
    • water, because it melts at 0 °C and boils at 100 °C
    • ammonia, because it is a liquid
    • oxygen, because it is a simple molecule
    Check

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

    15. Which substance, other than Substance Y, is a liquid at room temperature?

    • magnesium oxide
    • Substance X
    • ammonia
    • bromine
    Check

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

    16. Why does magnesium oxide have very high melting and boiling points?

    • It contains water.
    • It is made of small molecules with weak forces between them.
    • It is a giant ionic lattice with strong attraction between the ions, which takes a lot of energy to break.
    • Its atoms share electrons in small molecules.
    Check

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

    17. Why does ammonia have low melting and boiling points?

    • It is a giant ionic lattice.
    • Its covalent bonds inside each molecule are weak.
    • It is made of simple molecules with weak forces between them.
    • It is a macromolecule.
    Check

18. 18. Diamond and graphite are both made of carbon atoms. Which describes the structure of graphite?

    • flat layers of carbon atoms in hexagons, stacked on top of each other
    • a lattice of positive and negative carbon ions
    • each carbon atom joined to four others in a rigid 3D network
    • separate small molecules of carbon
    Check

19. 19. Why is graphite soft and slippery?

    • It contains water between the atoms.
    • Its covalent bonds are weak.
    • Its layers are held together by weak forces, so they slide over each other.
    • It is made of ions that can move.
    Check

20. 20. Why is diamond the hardest natural material?

    • Its ions attract each other.
    • Its layers can slide over each other.
    • Every carbon atom is joined by strong covalent bonds to four others in a rigid 3D network.
    • It is made of small molecules.
    Check