[Part 2]- C8- the rate and extent of chemical change 💥

• when the temperature, it increases the rate of reaction • ; when the temperature decreases, this decreases the rate of reaction.

• increasing the temperature, increasing the rate of a [chemical] reaction. • This is because, an increase in temperature, increases the speed at which particles can move. • This then increases the number of collisions that occur, as they now collide more frequently. • and because the number of collisions occurring is increased, this increases the energy of the collisions. • Increasing the energy of the collisions, increases the number of particles that now have energy greater than the activation energy, [because they have overcome the activation energy barrier] • and because of this, this increases the chance of successful collisions [fruitful collisions]= which increases the rate of reaction.

• increasing the temperature, increases the speed of the particles. • this is because, it increases the number of successful collisions, and the rate at which they collide, is now more frequent. • therefore, this increases the rate of reaction

• Because the rate of reaction increases with temperature, the rate of reaction is proportional to the temperature.

• decreasing the temperature, decreases the speed of the particles. • this is because, it decreases the number of successful collisions, and the rate at which they collide, is now less frequent. • since at a lower temperature, they move slower and don’t collide with each other frequently • therefore, this decreases the rate of reaction

• concentration, is a measure of how much solute, is dissolved in a solvent [such as water]

• increasing the concentration of reactants in a solution, increases rate of reaction. • This is because, increasing the concentration, means there’s more particles available to collide. • This then means the collisions are more frequent, since this increases the frequency of having a [successful] collision- meaning this increases the rate of reaction.

Fill in the gaps: Because the rate increases if we increase the concentration, the rate is proportional to the concentration.

• pressure, is the force exerted, divided by the area on which it is exerted. • [and it’s usually measured in pascals (Pa) ]

• increasing the pressure, increases rate of reaction. • This is because, increasing the pressure, pushes and squashes the particles close together. • This then increases the chance of having a [successful ] collision because, the collisions are more frequent [and therefore this also increases they chance they will react.] • and this, increases rate of reaction.

• increasing concentration increases the rate of reaction. • and decreasing concentration, decreases the rate of reaction

• increasing pressure increases the rate of reaction. • and decreasing pressure, decreases the rate of reaction

• pressure is affected by the number of molecules. • the is because, the more molecules/ moles of a gas there are, the higher the pressure. • therefore, gas pressure can be increased, by squeezing it’s given mass, into a smaller volume

• changing pressure has no effect on rate of reactions, for some reactions because: • changing the pressure on a reaction which involves only solids or liquids has no effect on the rate. [as it doesn’t involve a reacting gases]

• gas pressure only involves reacting gases because: • gas pressure is caused by the force exerted by gas molecules, colliding with the surfaces of objects • gases are compressible, unlike liquids or solids

• a catalyst, is a substance that increases [speeds up] the rate of chemical reactions; it remains chemically unchanged itself, at the end of the reaction.

• catalysts provide an alternative reaction route, and this alternative reaction route has a lower activation energy.

• catalysts provide an alternative reaction route which has a lower activation energy. • this means, the particles require less energy, to cross the activation energy barrier • and because the particles require less energy to cross the activation barrier, the a higher proportion of the reactant particles, have energy to react. • meaning, the frequency of effective and successful collisions increases, therefore rate of reaction increases.

• the rate of reaction, depends on the number of particles that have energy to cross the activation barrier, and collide successfully

• we don’t include catalysts in the chemical equation, for a reaction. • different reactions, need different catalysts • and, enzymes act as catalysts in living organisms

• we don’t include catalysts, in the chemical equation, for a reaction because: • catalysts remain chemically unchanged at the end of a reaction [they’re not used up in the reaction] • and, catalysts are not a reactant.

• adding a catalyst, increases the rate of [a chemical] reaction

• For example, Nickel is a transition metal and catalyst, that is used to make margarine by hardening vegetable oil [through the process of hydrogenation]

• iron, is used to make ammonia by the Haber Process • platinum, is used in the manufacture of nitric acid [Ostwald process]