Starter quiz
- Match the following key words to their definition.
- endothermic⇔energy is transferred from the surroundings to the reaction ✓
- exothermic⇔energy is transferred from the reaction to the surroundings ✓
- Which of the following statements about chemical reactions are correct?
- all atomic bonds are broken before new ones are made
- particles must collide with enough energy to react ✓
- reactants form products ✓
- a chemical reaction is always exothermic
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- The rate of a chemical reaction is equal to the amount of product formed per unit ______.
- 'time' ✓
- A chemical reaction produces 0.5 g of gas in 10 seconds. Which is the correct rate of reaction?
- 0.5 grams
- 10 seconds
- 0.05 grams per second ✓
- 0.05 seconds per gram
- 0.05
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- The rate of a reaction can be changed by varying concentration or temperature, but also by changing the ______ of a solid reactant.
- 'surface area' ✓
- Which of the following statements about catalysts is incorrect?
- a catalyst speeds up a reaction without being used up or chemically changed
- catalysts are specific; different reactions require different catalysts
- enzymes are biological catalysts that speed up reactions in living cells
- reactions need catalysts to start and only take place when a catalyst is present ✓
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Exit quiz
- Match the following key terms to their definition.
- irreversible reaction⇔reactants form products, and the reaction goes to completion ✓
- reversible reaction⇔both forward and backward reactions occur under the correct conditions ✓
- Which of the following symbols is used to indicate a reversible reaction?
- →
- ↔
- ⇄
- ⇌ ✓
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- In reversible reactions, the forward and backward reactions have different energy changes. When energy is taken in from the surroundings, the reaction is called an ______ reaction.
- 'endothermic' ✓
- True or false? In a reversible reaction, the forward reaction needs to reach completion before the backward reaction can start.
- True
- False ✓
- The direction of reversible reactions can be influenced by changing conditions, such as temperature. By cooling a reaction down, the system will change to favour the ______ reaction.
- 'exothermic' ✓
- Match the following key words to their definition.
- hydrated⇔contains water molecules in its crystal structure (dot in the formula) ✓
- anhydrous⇔does not contain any water molecules in the crystal structure ✓
Worksheet
Presentation
Video
Lesson Details
Key learning points
- Different types of arrows (→, ⇌) are used in chemical equations to indicate the nature of the reaction.
- Reversible reactions are symbolised using the double-headed arrow (⇌) in chemical equations.
- In a reversible reaction, both the forward and reverse reactions can occur under the right conditions.
- hydrated copper sulfate (blue) ⇌ anhydrous copper sulfate (white) + water
- ammonium chloride ⇌ ammonia + hydrogen chloride
Common misconception
Pupils often think that a reversible reaction will always go to completion in one direction before reversing.
Explain that in a reversible reaction, if the conditions allow it, both the forward and backward reaction can occur at the same time.
Keywords
Reversible reaction - A chemical reaction where the reactants form products that, in turn, react together to reform the reactants.
Hydrated (salt) - A salt that contains water molecules within its crystal structure, shown by a dot in its formula, e.g. hydrated copper(II) sulfate (CuSO₄·5H₂O).
Anhydrous (salt) - A salt that does not contain any water molecules in the crystal structure, e.g. anhydrous copper(II) sulfate (CuSO₄).
Double-headed arrow (⇌) - Used to show that a chemical reaction is reversible.
Single-headed arrow (→) - Used to show the direction of an (irreversible) chemical reaction, showing that reactants form products.