C5

Question 1

What is an exothermic reaction?

Answer 1

An exothermic reaction is one which transfers energy to the surroundings, usually by heating. This is shown by a rise in temperature.

Question 2

What is an endothermic reactions?

Answer 2

And endothermic reaction is one which takes in energy from the surroundings. This is shown by fall in temperature.

Question 3

What are two examples of exothermic reactions?

Answer 3

• hand warmers use exothermic oxidation of iron in air to release energy.
• self heating cans of chocolate and coffee also rely on exothermic reactions between chemicals in their bases.

Question 4

What’s an example of an endothermic reaction?

Answer 4

•sports injury packs where the chemical reaction allows the pack to become instantly cooler without having to put it in the freezer

Question 5

How do you test to see how much energy is being absorbed or released?

Answer 5

By doing an experiment to test the effect of acid concentration on the energy released in neutralising the reaction between hydrochloric acid and sodium hydroxide.

Question 6

What experiment do you do to test how much energy is released or absorbed in a reaction?

Answer 6

1) Put 25cm^3 of hydrochloric acid and sodium hydroxide in separate beakers.
2) place the beakers in a water bath set to 25°C until they’re both the same temperature
3) have the hydrochloric acid followed by the sodium hydroxide to a polystyrene cup with a lid
4) take the temperatures of the mixture every 30 seconds and record the highest temperature
5) repeat steps 1 to 4 using different amounts of hydrochloric acid.

Question 7

What are reaction profiles?

Answer 7

Reaction profiles are diagrams that show the relative energies of the reactants and products in reaction and how the energy changes over the course of the reaction

Question 8

When bonds are broken, what type of reaction is used?

Answer 8

Endothermic

Question 9

When bonds are formed, what type of reaction is used?

Answer 9

Exothermic