Chemical reactions

Oxidation

(a) The gain or addition of oxygen by an atom, molecule or ion. (b) The loss or removal of electrons from an atom, ion or molecule. (c). An oxidizing agent is the species that gives the oxygen or removes the electrons.

Reduction

(a) The removal of oxygen in a compound. (b) The gain or addition of electrons to an atom, molecule or ion (c) A reducing agent is the species that removes the oxygen and "donates" the electrons. An easy way to memorize the electron part of oxidization and reduction is : OILRIG Oxidation Is Loss, Reduction Is Gain. (In terms of electrons)

Catalyst

Catalysts increases the rate of reaction, but the catalyst is not used up in the reaction. Basically, you can reuse the catalyst after a reaction because it is unchanged.

Devise a suitable method for investigating the effect of a given variable on the speed of a reaction

Concentration Remember, we did the experiment on Point 2. Repeat the experiment again, however, this time use two different types of concentrations of HCl. For one experiment use, "x" concentration of HCl For the second experiment, use "2x" concentration of HCl Temperature Again, repeat the experiment but this time with two different types of temperatures of HCl, and compare the differences of Volume of Gas produced. As you use a higher temperature, we see a steeper graph, hence concluding that a higher temperature leads to a higher rate of reaction. Surface Area Repeat the experiment again but this time use two different sizes of magnesium. The magnesium's you should use are: 1) Normal magnesium chips 2) Magnesium chips of same mass, but smaller pieces. Catalysts Again, repeat the experiment two times again, once with a catalyst, and once without.

Redox

Redox reaction is a reaction with involves both oxidation and reduction. In a nutshell, OIL RIG happens simultaneously.

Describe the effect of concentration, particle size, catalysis and temperature on the speeds of reactions

Surface Area Increasing the surface area will subsequently increase the rate of reaction, as increasing surface area will increase the chances of particles colliding with each other and will hence increase the rate of reaction. In the exam, they might ask you questions like, "which reacts faster, magnesium or magnesium powder". The obvious answer is the powder because the powder has a much larger surface area, hence increasing the rate of reaction. Concentration Increasing the concentration increases the rate of reaction, as there will be collisions per second per unit volume. The reason for this is increasing the concentration results in there being more particles in each cm3 of space, so there will be more frequent collisions between particles. As the reaction occurs and the reactants get slowly used up, the concentration of the substance then decreases. This explains for a slower rate of reaction as the reaction proceeds for a period of time. Temperature Increasing the temperature will increase the rate of reaction. There are two important reasons for this: Particles will move faster and have more kinetic energy so there will be more collisions per second. More colliding particles will have the necessary activation energy required, hence allowing more successful collisions. The second reason is a more important factor in explaining the increased rate of reaction than that of the first. Catalysts Adding a catalyst increases the rate of reaction, but it itself is not used up in the reaction. Catalyst speed up the reaction by lowering the activation energy or providing an alternative pathway for the reacting particles.

Describe and explain the effects of temperature and concentration in terms of collisions between reacting particles (concept of activation energy will not be examined).

Temperature: Increasing the temperature of will give the particles more kinetic energy, so the frequency of collisions between particles will increase and the number of successful collisions will also increase. Concentration: Increasing concentration increases rate of reaction.The reason for this is increasing the concentration results in there being more particles in each cm3 of space, so there will be more frequent collisions between particles. As the reaction occurs and the reactants get slowly used up, the concentration of the substance then decreases. This explains for a slower rate of reaction as the reaction proceeds for a period of time.

Example of redox

The iron(III) oxide is reduced to iron, the carbon monoxide is oxidised to carbon dioxide Since both oxidation and reduction occur here, this is an example of a redox reaction.