Chemical changes flashcards

Chemical changes involve reactions that produce new substances with different properties. Students must understand oxidation and reduction in terms of oxygen transfer and electron transfer, how to identify oxidising and reducing agents, and the reactivity series of metals. The topic covers displacement reactions, reactions of metals with acids and water, and how to extract metals from their ores. Electrolysis is also key, including how ionic compounds conduct electricity when molten or dissolved, what happens at each electrode, and the products formed during the electrolysis of brine and molten compounds. Understanding half equations and predicting products are important higher-level skills.

1. Card 1

   What is an oxidation reaction in terms of oxygen?

   Oxidation is the gain of oxygen by a substance during a chemical reaction.

2. Card 2

   What is a reduction reaction in terms of oxygen?

   Reduction is the loss of oxygen from a substance during a chemical reaction.

3. Card 3

   What is oxidation in terms of electron transfer?

   Oxidation is the loss of electrons. A substance that loses electrons is said to be oxidised.

4. Card 4

   What is a reducing agent?

   A reducing agent donates electrons to another substance, causing it to be reduced. The reducing agent itself is oxidised in the process.

5. Card 5

   What does the reactivity series tell us?

   The reactivity series ranks metals from most to least reactive, helping predict whether displacement reactions will occur and how metals are extracted.

6. Card 6

   What happens in a displacement reaction?

   A more reactive metal displaces a less reactive metal from its salt solution, taking its place in the compound.

7. Card 7

   How are metals extracted from their ores?

   Metals above carbon in the reactivity series need electrolysis; metals below carbon can be extracted by reduction with carbon in a blast furnace.

8. Card 8

   What conditions allow an ionic compound to conduct electricity?

   An ionic compound conducts electricity when molten or dissolved in water, because the ions are then free to move and carry charge.

9. Card 9

   What happens at the cathode during electrolysis?

   The cathode is the negative electrode. Positive ions (cations) are attracted to it and gain electrons, so reduction occurs here.

10. Card 10

    What happens at the anode during electrolysis?

    The anode is the positive electrode. Negative ions (anions) lose electrons here, so oxidation occurs at the anode.

11. Card 11

    What are the products of electrolysis of brine?

    Electrolysis of brine produces chlorine gas at the anode, hydrogen gas at the cathode, and sodium hydroxide solution is left behind.

12. Card 12

    Why is aluminium extracted by electrolysis rather than with carbon?

    Aluminium is more reactive than carbon, so carbon cannot reduce aluminium oxide; electrolysis of molten aluminium oxide is needed instead.

• Students often confuse the anode and cathode, forgetting that oxidation always occurs at the anode and reduction at the cathode.
• Many students think any metal can be extracted using carbon, but metals above carbon in the reactivity series require electrolysis instead.
• A common error is mixing up the reducing agent and the substance being reduced; the reducing agent is itself oxidised.

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