Topic 5 Chemistry

Chemical reactions consist of old bonds being broken in the process of new bonds being formed. Endothermic reactions have energy supplied to break the bonds. Exothermic process have energy released when new bonds are formed,

An exothermic reaction is one that gives out energy to the surrounding area in the form of heat by the rise in temperature. The heat energy is released in the forming of the bonds in the product is greater then the energy used in breaking the old bonds in the reactants.

Burning feuls is an exothermic reaction as to create the new bonds in the product such as water and carbon dixoide produces more energy then to break the bonds. This is the case in explosions.

An endothermic reaction is one that takes in energy from the surrounding area in the form of heat which causes a fall in temperature. The energy required to break the old bonds in the reactant is greater then the heat energy released when new bonds are formed in products.

Photosynthesis uses light energy from the sun to convert it into carbon dioxide and water into glucose and oxygen. When ammonium nitrate dissolves in water, it takes in heat energy to do this.

The energy profile diagram for endorthermic reactions has the product higher than the reactant as it absorbing the heat energy therefore the product is gaining energy. The difference in height represents the energy taken in during the reaction. In the exothermic the reactant is higher then the product as the reactants are loosing energy.

You would measure the temperature change for

• dissolving salts in water
• neutrilisation reactions (base+ acid)
• displacement reaction
• precipitation reaction

Measure the energy produced by measuring the temperature of the reactant then doing the reactions and measuring the temperature after to calculate the temperature change. By placing the polystryene cup into the beaker with cotton wool insulate it mores and a lid is placed to reduce the energy lost by evaporation a little bit.

Rate of reaction depends on the temperature, concentration, catalyst and surface area of a solid- or the size of the particle.

Reactions take place when particles collide with a certain amount of energy. The minimum amount of energy needed to…