Introduction After learning more about rates of reaction we are now given four different experiments to do. The aims of these experiments are to investigate the effect on the rates of reaction caused by temperature, surface area, concentration and catalyst. Background knowledge Reactants are the chemicals you start off with, the products are chemicals you produce and the activation energy is the amount of energy which colliding particles must have in order to start a chemical and change reactant particles into products.
This energy is used in the breaking of chemical bonds What is Rate of Reaction? Rate is a measure of the change that happens in a single unit of time. Rate of reaction is the speed of a chemical reaction calculated by measuring how quickly reactants change into products. The rate of a particular chemical reaction is affected by various factors like temperature, concentration, surface area and catalyst. In a chemical reaction starting materials are called reactants and the finishing materials are called products. It takes time for a chemical reaction to happen.
If the reaction only takes a short time to change into the product then that reaction will be assumed as a fast reaction and the rate of reaction is high. If the reaction takes long time to change in to product it is a slow reaction. The speed or the rate of reaction is slow. To measure rates of reaction you need to measure the amount of reactant used up per unit of time or the amount of product produced per unit of time WHAT FACTORS EFFECT THE RATE OF REACTION? The rate of reaction is the time taken for a reaction to complete, from beginning to end.
The time is started when the chemicals are first added together. Key factors that affect the rate of reaction are: 1. Temperature 2. Concentration of chemicals 3. Surface area 4. The introduction of a catalyst Temperature If the temperature of the reaction is increased, it speeds up the rate of reaction. This is because when heat is added, particles are given more energy. This makes them move faster and collide with more force. This means that collisions between particles are more likely, speeding up the rate of reaction. NORMAL TEMPERATURE INCREASED TEMPERATURE.
So, raising the temperature makes particles more often in a certain time, and makes it more likely that collisions result in a reaction. Because there are more effective collisions in the reaction, if you raise the temperature of the reaction from 10i?? C to 20i?? C, you roughly double the rate of reaction in many experiments. Concentration: If the concentration of either, or both of the chemicals is increased, this speeds up the rate of reaction. This is because there are more particles to collide with. The more collisions between particles in a given time, the faster the rate of reaction.
For example: An experiment that is often used to explain how concentration affects the rate of reaction is between sodium thiosulphate (at different concentrations) and HCl in same concentration Low concentration High concentration Surface Area Surface area is a measure of how much surface area is exposed. As we increase the surface area, we increase the rate of reaction. Increasing the surface area increases the number of collisions that are taking place. For Example: In an experiment with different sized marble chips and HCl the rate of reaction is faster when the marble chips have there largest surface area, when they are in powder form.
The rate of reaction is slowest when the surface area is at its highest, when the marble is in a solid block. Catalyst A catalyst is a substance, which speeds up a chemical reaction. At the end of the reaction the catalyst is chemically unchanged. The energy needed to start a reaction is called its activation energy. A catalyst lowers the activation energy. Catalysts make it easier for particles to react. With a catalyst, a lot more particles have enough energy to react, there for increasing the rate of reaction. The Collision Theory Reactions usually require collision between reactant molecules or atoms.
The formation of bonds requires atoms to come close to one another. New bonds can form only if the atoms are close enough together to share electrons. Some collisions are not successful. These are called unsuccessful collisions Collisions that lead to products are called successful collisions. A successful collision must happen with a great enough speed, energy and force to break bonds in the colliding molecule. It must have activation energy Safety Precautions While doing these four experiments we have to take care of all the safety requirements such as:
– Keep all items involving glass away from the edge of the table to help and accident proceeding – Wear all laboratory equipments such as coats, goggles, gloves etc – Don’t mess around in the laboratory with dangerous chemical such as Acid Types of reaction There are two types of reaction – Exothermic – Endothermic When the heat is given out it is an exothermic reaction. We know this because the surroundings get warm. In an endothermic reaction, energy is taken in from the surroundings. The surroundings then have less energy than they started with, so the temperature falls. Aim.
My aim in this experiment is to find out whether or not a rate of reaction is affected by changing in the temperature. Apparatus needed during experiment:(shown with diagrams) Bunsen Burner Test Tube stopwatch thermometer Clamp and stand tripod HCL Magnesium Strips Fair Test To keep the test fair there are a list of variable that will need to be noticed are: Concentration-Increasing the concentration of the acid will reduce the amount of water particles in the acid therefore decreasing the chances that the acid particles have of being obstructed by the water particles instead of colliding with the magnesium particles
Temperature- Increasing the temperature in the reaction will result in the acid particles gaining more energy and therefore moving more quickly and hitting the magnesium more and more increasing the chance of successful collisions. Surface Area- Increasing the surface area of the magnesium will expose more particles to the acid therefore reducing the time it takes for the reaction to finish as it has a larger surface to attack. Stirring-Stirring the solution will give the acid particles extra movement energy and increase their speed hitting the magnesium more and more increasing the amount of successful collisions.
Volume Of Acid- Increasing the volume of the acid would increase the amount of particles in the solution therefore increasing the chance of collisions with the magnesium. However this would be limited by the size of the magnesium. Catalyst- Adding a catalyst to the solution sparks in itself a reaction which would give the particles in the solution more energy and increase their movement rate therefore increasing the chance of collisions between the acid and the magnesium particles. The Word equation for this experiment Magnesium + Hydrochloric Acid Magnesium chloride + Hydrogen.