Reaction Between Potatoes Catalyse On Hydrogen Peroxide example essay topic

DECOMPOSITION OF HYDROGEN PEROXIDE BY THE ENZYME CATALYSE POTATO. Introduction In the investigation we will be finding out how the reaction between Potatoes catalyse on Hydrogen peroxide (H 2 O 2) can study the effect of concentration on rate of reaction. The potato is the enzyme that will decompose the chemical Hydrogen peroxide. Hydrogen peroxide is a poisonous chemical, which is broken down in to water (H 2 O) and oxygen (O 2). Aim Investigating the decomposition of hydrogen peroxide by using potato catalyse, which is a biological catalyst. Using concentration for the experiment, to see whether this has any effect on the rate of reaction.

Prediction That the more dilute the hydrogen peroxide becomes, the rate of reaction will decrease. This is because as there is a decrease in hydrogen peroxide particles and an increase of water the hydrogen peroxide are more further apart from the potato catalyse; this decreases the collision of the hydrogen particles. Making it difficult for the reaction to occur faster. However, when there is a stronger concentration of hydrogen peroxide, the particles will be much closer allowing the reaction to occur faster. The word equation for this reaction is: - Catalyse enzyme + Hydrogen peroxide Water + oxygen In dilute hydrogen peroxide, the reaction takes places slower, for the water, particles have taken much of the space needed for the reaction. The stronger the concentration of the hydrogen peroxide, the faster the reaction will take place since there is more particles and space for the reaction to take place Water particle.

Enzyme catalyse. Hydrogen peroxide Quanta tive Prediction That as 2 ml of water is put in the hydrogen peroxide the number of bubbles produced will decrease approximately by a fifth. Knowledge Enzyme Enzymes are large proteins that speed up chemical reactions. In their spherical structure, one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, or the location on the enzyme where the substrate binds and the reaction takes place. Enzyme and substrate fail to bind if their shapes do not match exactly. This ensures that the enzyme does not participate in the wrong reaction.

The enzyme itself is unaffected by the reaction. When the products have been released, the enzyme is ready to bind with a new substrate. Diagram how an enzyme breaks a substrate into products. Enzymes properties 1. They are all protein. This is one reason why we need protein in our food.

2. They are specific in their action. This means that each enzyme controls one particular reaction, or type of reaction, e.g. Maltase will only act on maltose or sucrase on sucrose. 3. They can be used over again. This is because they are not altered or affected by the reaction.

4. They are destroyed by heat. This is because enzymes, being proteins are denatured by heat. Most enzymes stop working if the temperature rises above 450 C. However, certain microbes have enzymes, which can work at higher temperatures. 5. They are sensitive to pH.

The pH is the level the solution is at, being either acidic (1-6) or an alkali (8-14). Most intracellular enzymes work best in neutral conditions i.e. conditions that are neither acidic nor alkaline. The digestive enzymes work best in acidic conditions, and those on the small intestine work best in alkaline conditions. Word and Symbol equations of the experiment Word equation: - Enzyme + Hydrogen peroxide Water + Oxygen Symbol equation: - Enzyme + H 2 O 2 H 2 O + O 2 Collision theory Theory that explains how chemical reactions take place and why rates of Reaction alters.

For a reaction to occur the reactant, particles must collide. Only a certain fraction of the total collisions cause chemical change; these are called fruitful collisions. The fruitful collisions have sufficient energy (activation energy) at the moment of impact to break the existing bonds and form new bonds, resulting in the products of the reaction. Increasing the concentration of the reactants and raising the temperature bring about more collisions and therefore more fruitful collisions, increasing the rate of reaction. When a catalyst undergoes collision with the reactant molecules, less energy is required for the chemical change to take place, and hence more collisions have sufficient energy for reaction to occur. The reaction rate therefore increases.

This theory says that: - o All materials (even solids) are made up of tiny moving particles. o Particles of different substances have different sizes. o The particles are always moving. o As the temperature rises, the particles move faster. o At a given temperature, small particles move faster than heavier particles. o If the particles do not come in contact, the reaction does not take place. Diagram showing how a collision between particles occurs: - A fruitful collision: A B A B A B A B A B A B Unstable activated Complex. An Unfruitful collision: Collision theory explains how chemical reactions occur and why rates of reaction differ. For a reaction to occur, particles must collide. If the collision causes a chemical change, it is referred to as a fruitful collision.

Lock and key theory Substrate: The enzyme, which the enzyme breaks down. Product: The substance, which is broken down in to a completely different substance. Enzyme: A protein called an enzyme, which break down the substrate. The lock and key theory explains to us as to how an enzyme would act a substance and how it is specialised in doing its job. How it works: - 1. The substrate first comes in contact to the enzyme.

1. The enzyme locks the substrate to it. 2. The enzymes active site breaks down the substrate into a completely different substance called the products.

3. Products leave the enzyme, and the enzyme is now ready to decompose another substrate. Kinetic theory This theory describes the physical properties of matter in terms of the behaviour - principally movement - of its component atoms or molecules. The temperature of a substance is dependent on the velocity of movement of its constituent particles, increased temperature being accompanied by increased movement. A gas consists of rapidly moving atoms or molecules and, according to kinetic theory; it is their continual impact on the walls of the containing vessel that accounts for the pressure of the gas. The slowing of molecular motion as temperature falls, according to kinetic theory, accounts for the physical properties of liquids and solids, culminating in the concept of no molecular motion at absolute zero (0 K/-273 oC).

Affecting factors There are other factors, which affect rate of reaction. They are: - temperature and surface area. These factors affect the rate of reaction, because they can change the reaction speed. Either by the movement of the particles or the amount of space for more reactions to take place. These factors are important because the size of the catalyse can alter in size and the temperature can decrease or increase around the test tube. Information The information was gathered from previous investigation and from textbooks, CD-ROMS, encyclopaedias.

Fair test In order to make this experiment a fair test. To make sure that during each experiment the hydrogen peroxide was measured accurately during each experiment. To also make sure that the potato catalyse had a fixed mass, making sure this was correct. Weighed potato catalyse on a scale.

Throughout the experiment, the mass kept the same at 3 grams. To make sure that there was no error made during the experiments the test-tube was rinsed thoroughly. This will make the experiment a fair test. Safety To make a safe experiment the hydrogen peroxide did not come in contact with the mouth, and eyes. This is because hydrogen peroxide is a poisonous chemical and also corrosive especially to the eye making it burn. To protect the eyes, goggles have to be kept on throughout the experiment.

To make sure that the chemical will be disposed of safely. Also, make sure not cut yourself with the knife (to cut potato catalyse). Plan To gather all the equipment needed. Then set up the experiment, weighing and measuring the reactants carefully.

Then start the experiment concentrating on the number of bubbles produced, making sure are group do not miss any bubbles made. This information will all be recorded on a set of results tables. The experiment will be carried out three times for a repeats table, for results that are more accurate. After the experiment, all the equipment will be put away. Then a forth table will be made as the average table.

Diagram Apparatus o Delivery tube o Test tube o Test tube rack o Hydrogen peroxide (H 2 O 2) o Knife o Scale o Water o Results book o Goggles o Stop watch o Measuring cylinder o Beaker (for H 2 O) o Beaker (for H 2 O 2) Results Plan The results will have a pattern. As the more water (increase in water by 2 ml in each experiment) is added to the hydrogen peroxide then the less bubbles will be produced. So as the further down we go down the results table the number of bubbles will decrease. It will decrease by a fifth (going down the results table). Diagram showing how the results table will look like: - Experiment one total time- 1 minutes. 30 sec?

45 sec? 60 sec? Plan (good / bad ) This plan is a good way of setting out an experiment and keeping safe. By doing this, it is organised and makes the experiment clear.

Patterns in results table That as you go down each column of the table the number will increase and when you go from left to right on each row the number decreases. The use of my equipment The list of apparatus above will enable to obtain precise results, and to minimise any errors. Good range The experiment will be carried out twice to obtain an average, thus reducing the outcome of any anomalous results. The concentration from 100% of Hydrogen Peroxide to 20%.

There will be 5 sets of readings. Method The apparatus was set up shown on the apparatus diagram. Measure the hydrogen peroxide to 10 cm 3 before starting the experiment. To do this you had to level your eyes with the cylinder to the amount, measuring the 10 cm 3 hydrogen peroxide. This point is called the lower meniscus, as shown below. This was done to both of the substances (H 2 O 2, and H 2 O).

After having measured the hydrogen peroxide, the potato catalyse was then cut into cubes with a mass of 3 gram with the use of a scale. The potato catalyse was then put into the test tube, and then set the stopwatch. As soon as the H 2 O 2 was poured into the test tube, it was covered with the rubber bung (attached to it the delivery tube), and then started the time. The numbers of bubbles produced in the other test tube were all counted. At the end of the first part of the experiment, the results were written down. The test tube was cleaned and then ready to start the next part of the experiment.

In this experiment, 2 ml of water and 8 ml of hydrogen peroxide was experimented. Then did the same method in experiment one. At the end of the experiment including the repeat test, the outcome was three sets of results. The equipment was then put all away safely. This total was then divided by three, as there were three results for this, which gave the average.

The same procedure will be carried for the remaining concentrations used to investigate the decomposition of Hydrogen peroxide by the enzyme Potato Catalyse. It tells us how many bubbles were produced per second. The formula for this is: - Bubbles produced per second = Number of bubbles produced Time taken Average results Row one 18 = 0.3 60 Row two 12 = 0.2 60 Row three 10 = 0.16 60 Row four 4.3 = 0.0716 60 Row five 2 = 0.03 60 Calculations 2 The calculations below show you what the formula is for working the gradients for the results graph. The formula for this is: - Y 2 - Y 1 = GRADIENT X 2 - X 1 Average table graph Concentration = 100% Gradient = 18 = 0.3 x 100 = 30% 60 Concentration = 80% Gradient = 12 = 0.2 x 100 = 30% 60 Concentration = 60% Gradient = 10 = 0.16 x 100 = 16% 60 Concentration = 40% Gradient = 4.3 = 0.0716 x 100 = 7.16% 60 Concentration = 20% Gradient = 2 = 0.03 x 100 = 3% 60 Discussion After studying the results tables and knowledge, you can clearly see that as the more diluted the hydrogen peroxide (H 2 O 2) is the slower the rate of reaction. This is because by diluting the H 2 O 2 the number of oxygen (O 2) bubbles produced decreases.

However, if the hydrogen peroxide were to be more concentrated then the faster the rate of reaction. By looking at the amount of bubbles produced, it gives a clear proof as to how fast the reaction is going. The more diluted H 2 O 2 took long reacting, as there was less activation energy for there to be a collision, therefore the reaction was slow. However, if the H 2 O 2 were more concentrated then there would be a faster reaction, as there is enough activation energy for the H 2 O 2 to collide with the potato catalyst giving a reaction. Conclusion After studying the results table, calculations, and the graphs, I can clearly say that my prediction has been justified. My results prove my prediction.

The higher the concentration of hydrogen peroxide the faster the rate of reaction. The results also show that the research that I did also showed a valid pattern, as the concentration doubles the rate of reaction doubles. If my results had been more accurate then the results would show the concentration of the H 2 O 2 and the rate of reaction to be proportional. The graph also supports my prediction.

On the graph the steeper the curve, the faster the rate of reaction, also from the graph, I was able to work out the average rate of reaction from the gas produced. Evaluation Overall, I am pleased with my results and the way the experiment was carried out. The safety requirements were all met and was all carried out as planned. I think that my results are very accurate and proved my prediction.

To make the overall experiment results more accurate I repeated the experiment three times and did an average table. If I was to do this experiment again I would probably make it more accurate by using a Burette to measure the amount of gas given off, this would measure a lot more accurately the amount of gas given off. Also smaller blocks of potato so I could match up the surface area and weight more accurately each time. I would like to then see if the concentration of H 2 O 2 is proportional to the rate of reaction.

Looking at my results graphs clearly can be seen is that the steeper the curve line is the more bubbles produced in a certain time. That the less steep the curve then there is less bubble produced in a certain time. After 30 seconds the graph begins to curve and become less steep. This tells us that there is now less Hydrogen Peroxide to decompose. I had the time to make three sets of results due to the simplicity of the experiment, this why I chose this factor (concentration) to show the effect on the rate of reaction. The other things that I would like to investigate would be the experiment of time against the amount of gas produced to show at which points the rate of reaction was at best and the curve / line of reaction.

To also investigate other factors which affect the rate of reaction like temperature, and surface area to see how they affect the rate of reaction. There are some areas that need to be improved e.g. controlling the stopwatch. There are many human errors here. However, the inaccuracies due to them were negligible because I paid close attention to these during the experiment. The other improvements that I would like to make is to do different levels of concentration like for example 10%, 20%, 30%, etc..