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11.2 types of chemical reactions
Grade 8 explain chemical reactions
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Rates of Reaction
Reactions
Reactions can only occur when two different particles come together.
The theory for the way the reaction occurs is called The Collision
Theory.
The collision theory states that that the different particles need to
collide with each other in order to react. However, they do not react
if they collide without sufficient energy, and therefore the more
energy a particle has, the more likely it is to react. The activation
energy is the minimum amount of energy required by a particle in order
to react. When a rate of reaction is improved, the likelihood of the
collision of particles is higher and the energy at which they collide
is increased.
The importance of rates of reaction
The rate of a reaction is the speed at which this reaction occurs. In
different reactions, the rates are different. The two extremes are
iron rusting - extremely slow - and an explosion - so fast you cannot
tell what's going on!
In our body, there are plenty of reactions taking place every second,
in every cell, in order to provide the body with its requirements.
These reactions must occur at a certain speed so that the body runs in
a smooth manner; the reactions are timed perfectly with the
environment in the body.
The rate is very important, and not only in the body. When scientists
perform reactions in a lab, they cannot allow the reaction to take
very long.
When chemicals and medicine is made in an industry, the aim is to make
money. If the reactions take too long, the money is not made as fast
as it should be. Also if there is a crisis and medicine is urgently
needed, then the reactions would have to be significantly speeded up.
This tells us the importance of the speed of a reaction, and the rates
of reaction.
How are Rates of Reactions Measured?
In order to change the rate at which a reaction occurs we first must
measure the current rate and the rate after we have improved the
The rate law determines how the speed of a reaction occurs, thus allowing the study of the overall mechanism formation in reactions. In the general form of the rate law, it is A + B C or r=k[A]x[B]y. The rate of reaction can be affected by the concentrations such as A and B in the previous equation, order of reactions, and the rate constant with each species in an overall chemical reaction. As a result, the rate law must be determined experimentally. In general, in a multi-step reaction, there will be one reaction that is slower than the others.
For a reaction to occur, particles must collide. If the collision causes a chemical change it is referred to as a fruitful collision. (Hutchinson Educational Encyclopaedia, 2000) Enzymes increase the rate of exergonic reactions by decreasing the activation energy of the reaction. Exergonic reactions are those in which the free energy of the concluding state is lower than the free energy of the opening state.
The activation energy is reduced so that there is a better chance of particles having enough energy to react. Reactants will need less. energy to react to. 2. What is the difference between a..
If a reactant is a solid, then breaking it up into smaller pieces (but keeping the mass the same) will increase its surface area. If there is a larger surface area the reacting particles will have more of an area to react with, therefore there will be more collisions. 4. A catalyst works by giving the reacting particles something to stick to where they can collide with each other, because they are all attracted to the catalyst there are going to be more collisions. A catalyst does not get used up in a reaction.
Text Box: Surface Area When a solid reacts with a liquid or gas, the surface area of the solid particles makes a difference to the speed of the reaction. From the diagram you can see that the three smaller particles have a larger surface area all together (shown as blue) than the larger particle and so will react faster. There are more calcium carbonate particles on the the concentration of the hydrochloric acid
will result in an increase in the speed of the rate of reaction it has
cloudy, to test this; I will place a piece of paper with a cross on
Rate is determined on how fast something is being consumed in a reaction, or how
While measuring the effect of the use of a catalyst and temperature on the reaction rate, several factors must be kept constant. During the reaction with a catalyst, the temperature will be kept constant (at room temperature), concentration, pressure and since the reaction involves liquids, the surface area will be kept constant at all times, however they must be mixed the same.
Before conducting my experiment I will research into, amongst other things, the factors that affect the rate of a reaction. This is so that I may enough information to understand the effect of temperature on the rate of a reaction and also gain appropriate understanding to make a suitable prediction as to what the outcome of my experiment will be.
The time taken for this to happen is the measure of the rate of reaction. We must do this several times, and change the concentration of sodium thiosulphate. The rate of reaction is a measure of the change, which happens during a reaction in a single unit of time. The things that affect the rate of reaction are as follows. Surface area of the reactants Concentration of the reactants
Chemical kinetics is the study and examination of chemical reactions regarding re-arrangement of atoms, reaction rates, effect of various variables, and more. Chemical reaction rates, are the rates of change in amounts or concentrations of either products or reactants. Concentration of solutions, surface area, catalysts, temperature and the nature of reactants are all factors that can influence a rate of reaction. Increasing the concentration of a solution allows the rate of reaction to increase because highly concentrated solutions have more molecules and as a result the molecules collide faster. Surface area also affects a
One vital process in the human body observed in chemistry is the idea of chemical kinetics. Chemical kinetics is the study of the rate of reactions, or how fast reactions occur.1 Three factors that affect chemical kinetics are concentration, temperature, and catalysis. As the concentration of a substance increases, the rate of the reaction also increases.1 This relationship is valid because when more of a substance is added in a reaction, it increases the likelihood that the
To control the rates of chemical reactions is imperative to the continued existence of our species. Controlled chemical reactions allow us to move forward in society, constantly. We find new ways to provide light and heat our homes, cook our food, and pursue in crafts that benefit our society. There are, however, just as there are advantages, disadvantages to the efficiency of controlling the rate of reactions, which in some cases can be fatal to our scientific development and progression. The growth of humankind necessitates that we must be able to control the rate of chemical reactions.
t = time, a = volume of reactant, k is a constant of proportionality; x is the order of reaction. Because k is a constant of proportionality 1/t is directly proportional to the rate of reactant. Then to find out the order of reaction in a catalysed system the volume of ammonia molbydate is varied and the concentration of the other reactants kept the same. Thirdly to investigate the activation energies, the concentrations are kept the same and the temperature is varied.