Show — 5 marks
A student is investigating different substances used in everyday products. They examine salt (sodium chloride), sugar (sucrose), and copper metal. The student needs to understand how the atoms in these substances are held together.
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(a) Show that sodium chloride contains an ionic bond by describing what happens to the electrons when a sodium atom reacts with a chlorine atom.
[2 marks]
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(b) Sugar (sucrose) contains covalent bonds. Show the difference between an ionic bond and a covalent bond in terms of electron transfer or sharing.
[2 marks]
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(c) Explain why copper metal has a different type of chemical bonding compared to sodium chloride and sugar.
[1 mark]
Show mark scheme
- (a) Electron(s) transferred from sodium atom to chlorine atom (1 mark)
- (a) Sodium loses one electron / chlorine gains one electron / formation of Na+ and Cl- ions (1 mark)
- (b) In ionic bonding electrons are transferred between atoms / in covalent bonding electrons are shared between atoms (1 mark)
- (b) Ionic bonding forms ions / covalent bonding does not form ions / covalent bonding forms molecules (1 mark)
- (c) Copper contains metallic bonding / delocalised electrons / electrons free to move / metal atoms held together by attraction to sea of electrons (1 mark)
Suggest — 5 marks
A student is investigating different materials used in everyday products. They compare three substances: salt (sodium chloride), diamond, and oxygen gas. Each substance has different chemical bonds holding the particles together.
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(a) Suggest which type of chemical bond is present in salt (sodium chloride).
[1 mark]
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(b) Suggest why salt has a high melting point, whereas oxygen gas has a very low boiling point. In your answer, refer to the chemical bonds present in each substance.
[3 marks]
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(c) Diamond is used in cutting tools because it is extremely hard. Suggest how the type and arrangement of chemical bonds in diamond explains its hardness.
[1 mark]
Show mark scheme
- (a) Ionic bond(s) / ionic bonding
- (b) Salt contains ionic bonds which are very strong / require a lot of energy to break
- (b) Oxygen gas contains covalent bonds / weak intermolecular forces between molecules
- (b) Therefore salt has a high melting point and oxygen has a low boiling point / more energy is needed to break ionic bonds than intermolecular forces
- (c) Diamond has strong covalent bonds arranged in a continuous 3D network / structure, which makes it very hard to break / resistant to deformation
Show — 4 marks
A student is investigating the properties of three substances: sodium chloride (table salt), diamond, and hydrogen chloride gas. They want to understand why these substances have such different properties despite all containing chemical bonds.
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(a) Sodium chloride has a very high melting point of 801°C, whereas hydrogen chloride gas has a melting point of -114°C. Show that the type of chemical bonding in sodium chloride explains why it has a much higher melting point than hydrogen chloride.
[2 marks]
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(b) Diamond is a form of carbon with a melting point of 3550°C. Show why diamond's melting point is even higher than sodium chloride's, by referring to the structure and bonding in diamond.
[2 marks]
Show mark scheme
- (a) Sodium chloride contains ionic bonds (between Na+ and Cl- ions) / hydrogen chloride contains covalent bonds (between H and Cl atoms) - 1 mark
- (a) Ionic bonds are very strong and require a lot of energy to break, whereas covalent bonds in individual HCl molecules are strong but the intermolecular forces between HCl molecules are weak, so less energy is needed to separate the molecules - 1 mark
- (b) Diamond has a giant covalent structure / macromolecular structure where each carbon atom forms four strong covalent bonds to other carbon atoms in a continuous 3D network - 1 mark
- (b) All the bonds throughout the entire structure must be broken to melt diamond, requiring enormous amounts of energy, whereas in sodium chloride only the ionic bonds need to be broken (the ions can then move freely) - 1 mark
Calculate — 2 marks
Ammonia (NH₃) is an important chemical used to manufacture fertilisers for agriculture. Each ammonia molecule contains nitrogen atoms covalently bonded to hydrogen atoms. A student is drawing a diagram to show the bonding in one molecule of ammonia.
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(a) Calculate how many hydrogen atoms bond with one nitrogen atom in a molecule of ammonia.
[1 mark]
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(b) Calculate the total number of electrons shared between the atoms in one molecule of ammonia.
[1 mark]
Show mark scheme
- (a) 3 or three
- (b) 6 or six (allow ecf: 2 × their answer to 01.1)
Explain — 3 marks
Sodium chloride is an ionic compound commonly used in food preservation. In a school laboratory, a student observes that solid sodium chloride must be heated to 801°C before it melts, whereas candle wax melts at approximately 60°C.
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(a) Explain why sodium chloride has a high melting point.
[2 marks]
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(b) State the type of bonding present in sodium chloride.
[1 mark]
Show mark scheme
- (a) strong electrostatic forces of attraction between oppositely charged ions
- (a) large amount of energy required to overcome these forces / break the bonds
- (b) ionic (bonding)
GCSE Perfect