Energy Changes and Rates of Reaction

Reactions where a change of state takes place. They are easily reversible, no new substances are formed, and there is no change in mass

Atoms are rearranged. They are not easily reversible. New substances are formed, and substances involved can change mass

273 Kelvin

Particles are close together in a regular pattern. They do not move but vibrate. There are strong forces between particles, and they do not have much energy

There is some force between particles. They are close but in a random shape and can move around. They have more energy than solids but less than gases.

There is no force between particles and they can move freely. They have lots of energy and no set shape

Reactions where substances have more energy than they start with. They take in heat energy.

Reactions where substances have less energy than they start with. They give out heat energy.

Thermal decomposition, photosynthesis, some types of electrolysis, cooking

Combustion, respiration, neutralisation, reactions of metals and acids

Making bonds is EXOthermic, Breaking bonds is ENDOthermic

Energy is first supplied to break bonds, but then lots of energy is released when bonds are formed

Some energy is released making bonds, but then lots is supplied breaking bonds

Overall energy change = energy required to break bonds - energy released by forming bonds

The amount of energy needed to make or break a bond

A measure of how fast a reaction happens

Surface area, concentration or pressure, temperature

Rate of reaction = amount of reactant used or amount of product formed / time

Precipitation (disappearing cross) Change in mass (from gas given off) Volume of gas (using a gas syringe)

Draw a tangent (straight line) to the point at which you need to find the gradient and measure its gradient

They need to collide with a certain amount of energy or higher

Collision frequency and energy transferred

Activation energy

Using a catalyst