Edexcel IGCSEChemistryGeneral Applications9 Marks
This question is about elements and compounds. (a) Explain why metals are good conductors of electricity.
- (a)Explain why metals are good conductors of electricity.[2]
- (b)Lithium is an alkali metal. (i) Write the word equation for the reaction of lithium with water.[1]
- (b)(ii)Describe two observations when lithium reacts with water.[2]
- (b)(iii)Explain why lithium is less reactive than potassium.[2]
- (c)Magnesium reacts with oxygen to form magnesium oxide. Mg(s) + O₂(g) → MgO(s) Balance the equation for this reaction.[1]
- (d)Explain how magnesium oxide conducts electricity when molten.[1]
Mark scheme
Marking points from the official mark scheme. The mark or mark type is shown in brackets.
- M1 for (a) delocalised electrons / free electrons
- A1 for (a) which can move throughout the structure / carry charge
- B1 for (b)(i) lithium + water → lithium hydroxide + hydrogen
- B1 for (b)(ii) Any two from: lithium floats / moves on surface / fizzes / effervescence / gas produced / melts (into sphere) / disappears / solution turns pink/purple (with indicator)
- M1 for (b)(iii) lithium has fewer electron shells / outer electron closer to nucleus
- A1 for (b)(iii) outer electron less easily lost / more attraction to nucleus
- B1 for (c) 2Mg(s) + O₂(g) → 2MgO(s)
- B1 for (d) (molten) ions are free to move / carry charge
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