Starter quiz
- Match the following terms to their definitions.
- reactant⇔substance present at the start of a chemical reaction ✓
- product⇔substance made during a chemical reaction ✓
- chemical reaction⇔when chemical bonds are broken and new substances are formed ✓
- physical change⇔a reversible process that does not involve breaking chemical bonds ✓
- True or false? A change of state indicates that a chemical reaction has taken place.
- True
- False ✓
- Which of the following are examples of chemical reactions?
- oxidation ✓
- thermal decomposition ✓
- evaporation
- condensation
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- Hydrogen gas and magnesium chloride are formed when magnesium reacts with hydrochloric acid. Which of the following represents the chemical equation for the reaction?
- magnesium + hydrochloric acid → magnesium chloride + hydrogen ✓
- magnesium chloride + hydrogen → magnesium + hydrochloric acid
- magnesium chloride + hydrochloric acid → magnesium + hydrogen
- hydrochloric acid + hydrogen → magnesium + magnesium chloride
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- Burning is an example of ... Select two correct answers.
- a combustion reaction. ✓
- a neutralisation reaction.
- a thermal decomposition reaction.
- an oxidation reaction. ✓
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- Calculate the mass of carbon dioxide formed when 13.5 g of calcium carbonate reacts to form 7.6 g of calcium oxide. calcium carbonate → calcium oxide + carbon dioxide
- '5.9 g' ✓
Exit quiz
- Match the following terms to their definitions.
- exothermic chemical reaction⇔energy is transferred from the reactants to the surroundings ✓
- endothermic chemical reaction⇔energy from the surroundings is transferred to the products ✓
- dissipate⇔energy is transferred (and lost) as 'heat' to the environment ✓
- Endothermic reactions cause ...
- an increase in temperature of the surroundings.
- a decrease in temperature of the surroundings. ✓
- the temperature of the surroundings to remain the same.
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- Which of the following are reactions that are usually exothermic?
- combustion ✓
- thermal decomposition
- neutralisation ✓
- photosynthesis
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- The method for finding the lowest temperature of a reaction has been mixed up. Starting with measuring the volume of solution, sort the following steps into the correct order.
- 1⇔Measure 100 cm³ of copper sulfate solution into a polystyrene beaker.
- 2⇔Measure the temperature of the solution.
- 3⇔Add 2 g of ammonium nitrate powder.
- 4⇔Stir the solution until all of the ammonium nitrate has dissolved.
- 5⇔Measure the temperature of the reaction mixture.
- 6⇔Record the lowest temperature reached by the solution.
- A pupil monitored the temperature of a reaction. The start temperature was 20°C and the end temperature 15°C. Which of the following statements about the reaction are correct?
- The reaction is exothermic.
- The difference in temperature is –5 °C. ✓
- Energy is transferred from the surroundings to the products. ✓
- The temperature of the surroundings increased.
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- True or false? After an exothermic reaction, the products of the reaction contain more energy than the reactants.
- True
- False ✓
Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- An exothermic chemical reaction causes an increase in temperature (of the surroundings).
- An endothermic chemical reaction causes a decrease in temperature (of the surroundings).
- An exothermic reaction transfers energy from the reactants to the surroundings.
- An endothermic reaction transfers energy from the surroundings to the products.
Common misconception
The difference between the surroundings (where the reaction takes place, e.g. solution) and the environment (where the reaction mixture is, e.g. classroom). The existence of cold.
Use the separate terms of surroundings and environment throughout the lesson. Explain that thermal energy transfer only takes place from somewhere that is warmer and somewhere that is cooler.
Keywords
Exothermic chemical reaction - is a type of reaction in which energy is transferred from the reactants to the surroundings, e.g. combustion.
Endothermic chemical reaction - is a type of reaction in which energy from the surroundings is transferred to the products, e.g. photosynthesis.
Dissipate - Thermal energy can dissipate which means it can be transferred to the environment and wasted.
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