Exothermic and Endothermic reactions

How much energy is stored in Chemical Reactions?

Chemicals store a certain amount of energy - and different chemicals store different amounts

What happens if the product of a reaction store has more energy than the original reactants?

They must have taken in the difference in energy between the products and reactants from the surroundings during the reaction

What happens if the product of a reaction store has less energy than the original reactants?

The excess energy was transferred to the surroundings during the reaction

Law of conservation

Energy cannot be created or destroyed only moved around

Exothermic

Releases energy

Where does exothermic reactions release energy to?

To the surroundings

How are exothermic reactions shown?

A rise in temperature

An example of an exothermic reaction

Combustion

Everyday uses for exothermic reactions

Hand warmers, self heating cans

Endothermic

Absorbs energy

Where do endothermic reactions take in energy from?

The surroundings

How are endothermic reactions shown?

A fall in temperature

Examples of endothermic reactions

Thermal decomposition, photosynthesis

Everyday uses of endothermic reactions

Sports injury packs

How do you measure the amount of energy released by a chemical reaction?

Taking the temperature of the reagents, mixing them in a polystyrene cup and measuring the temperature of the solution at the end of the reaction

What are the problems with measuring energy transfer?

There may be energy lost to the surroundings

How do you reduce lost energy to the surroundings when measuring energy transferred?

Reduction by putting the polystyrene into a beaker of cotton wool to give more insulation, and putting a lid on the cup to reduce energy lost by evaporation

What are reaction profiles?

Diagrams that show the relative energies of the reactants and products in a reaction, and how the energy changes over the course of the reaction

Exothermic reaction profile

Products are at a lower energy than the reactants

Endothermic reaction profile

Products are at a higher energy than the reactants