Factors that could affect the rate of reaction
Below is a list of variables that could affect the rate of reaction. I would also be explaining how and why they affect it
Temperature
Temperature will affect the rate of reaction as we already know that in order for two particles to collide and react, energy is needed. This is the collision theory. By rising the temperature the mixture will contain more energy as the molecules involved in the reaction will have their energy levels raised. That increase in temperature will affect the particles as they will move faster so there will be more collisions. This is the kinetic theory and it will result in an increased rate of reaction. However because there are enzymes involved in this reaction, an increase in temperature past the enzymes optimum would result in them denaturing. I assume that the optimum of catalase is higher than room temperature (20 degrees); however I believe that this is satisfactory for my preliminary experiment to show the amount of oxygen produced for each material.
Surface area of the material containing catalase
Surface area will affect the rate of reaction as in conjunction with particle size; the smaller particles altogether will have a bigger surface area than the larger particle with the same mass. This is evident in simple things like chewing your food as this process breaks down the food into smaller pieces which will increase the surface area so the digestion of that food will be faster. In terms of this reaction, if I increase the surface area of the tissue containing catalase, it would result in the catalase enzymes being exposed to more of the hydrogen peroxide solution. For example a 5g sample of potato cut up into tiny pieces will have a greater combined surface area than a 5g chunk of potato. This would increase the rate of reaction. Also a bigger mass of the sample would result in more catalase that the tissue contains.
Concentration
Concentration will affect the rate of reaction as by increasing the concentration of catalase and the substrate molecules it will increase the amount of times that the enzyme collides with the hydrogen peroxide. Also if we take into account that when the two particles collide, it is not all the time that they will have enough energy to start a reaction as each of the molecules will have different energy levels. An increase in the concentration will increase the amount of collisions there are and will affect the amount of colliding molecules that do have sufficient energy levels to react together. If I increase the concentration of catalase this would mean that there are more enzymes in the solution. This would result in more reactions taking place, thereby increasing the rate of reaction.
Equipment
The equipment we used was the stop-clock, cork borer, Scalpel, Safety goggles, Tap water, Measuring cylinder, boiling tube, disposable plastic gloves, weighing boat, weighing scale, beaker, rubber tubing, and ceramic tile.
Scientific background knowledge
Enzymes are biological catalysts that speed up the chemical reactions in living organisms. Without enzymes, the human body would not be able to survive so it’s very important in processes in an organism such as the breakdown of food.
Basically enzymes are protein molecules that are made up of long-chain amino acids. While they may share this similarity, the length of the chains would vary which results in different enzymes which have different shapes. The specific shape of an enzyme plays a key role in its purpose.
Hydrogen peroxide is a clear liquid which is used often as bleach or cleaning agents and in high concentrations it is unstable and may even damage skin if it comes in contact with it. ‘It is also a powerful oxidizing agent that can cause spontaneous combustion when it comes in contact with organic material.’(1). although It is poisonous it is produced in organisms as a by-product of ‘oxidative metabolism’ (2). Nearly all organisms contain catalase so this harmful substance is broken down to less harmful products that are used by the body. This is helpful because if left by itself, the hydrogen peroxide would take too long to breakdown and lead to the death of the organism.
Lock and Key model
The lock and key theory was ‘first postulated in 1894 by Emil Fischer’. Essentially the substrates are the molecules which bind to the enzymes ‘active site’. Only the specific shape can fit into the active site because it is very specific. This means a different shape cannot fit into the active site thus no reaction will take place. A molecule with the right shape would form an enzyme-substrate complex and a reaction would take place until the substrate is broken down into the products.
Safety
Due to sodium thiosulpate being an irritant, we made sure that it didn’t come in contact with our skin it could potentially burn it. If this aqueous substance was to go on our skin we made sure that we were of reasonable distance to a water tap so the irritant could be rinsed of quickly before a reaction with our skin begins to occur. Also if it goes into our eyes I could really irritate and damage it so we made sure that goggles were worn.
Bibliography
