energy transfer in reactions

What is an exothermic reaction?

A reaction that transfers energy to the surroundings, increasing the temperature. Examples: combustion, oxidation, neutralisation

What is an endothermic reaction?

A reaction that takes in energy from the surroundings, decreasing the temperature.Examples: thermal decomposition

Everyday uses of exothermic reactions?

Everyday uses of endothermic reactions?

• Hand warmers and self-heating cans

• Sports injury packs.

In an exothermic reaction, how do the energy levels of reactants and products compare?

Products have less energy than reactants; the difference is released to surroundings.

In an endothermic reaction, how do the energy levels of reactants and products compare?

Products have more energy than reactants; the difference is absorbed from surroundings

How can you detect energy transfer in a reaction?

By measuring the temperature change of the surroundings.

What is the main problem with measuring temperature change in a reaction using a polystyrene cup?

Energy is lost to the surroundings.

How can you reduce energy loss in the temperature change practical?

Use cotton wool insulation and a lid on the cup.

Why is a polystyrene cup used in the practical?

It provides insulation to reduce energy transfer to the surroundings.

What’s one way to improve accuracy in the temperature change practical?

Use a lid to reduce energy loss by evaporation.

Describe the practical for investigating temperature changes in reactions.

1. Measure 25 cm³ of hydrochloric acid using a measuring cylinder.

2. Pour it into a polystyrene cup placed inside a beaker for stability.

3. Use a thermometer to record the acid’s starting temperature.

4. Measure 25 cm³ of sodium hydroxide solution and add it to the cup.

5. Stir the mixture and record the highest temperature reached.

6. Repeat the experiment with different concentrations of hydrochloric acid

What are safety precautions for practical

Wear eye protection due to corrosive and irritant chemicals.

How can you tell if a reaction is endothermic using the practical setup?

The thermometer shows a drop in temperature after mixing the reactants

How can you tell if a reaction is exothermic using the practical setup?

The thermometer shows a rise in temperatureafter mixing the reactants

What happens to the temperature in an exothermic reaction during the practical?

What happens to the temperature in an endothermic reaction during the practical?

-The temperature of the solution increases as energy is transferred to the surroundings.

-The temperature of the solution decreases as energy is taken in from the surroundings