'How dose concentration affect the rate of a chemical reaction.'

Biology SC1

‘How dose concentration affect the rate of a chemical reaction.’

Introduction

An enzyme is a protein molecule that speeds up chemical reactions in all living things. All living cells make enzymes but enzymes are not alive. Enzyme molecules function by altering other molecules. Enzymes combine with altered molecules to form a complex molcule structure in which chemical reactions take place.

Enzymes are specific, they only control one type of reaction although they are specific, all enzymes work in a very similar way and have similar properties. They are all globular proteins and are all biological catalysts, they increase the rate of a given reaction without being used up and their presence does not change the nature of the reaction or the end product. Enzymes work by having an actire site, made from amino acids. Here substrate molecules will bind with enzyme (and other substrate molecules if nesscesary) and a reaction takes place.

Enzymes function can be explained by the lock and key hypothesis.

The enzyme iself is not affected and releases, the new chemical after the reaction. After release of the end product, more substrate molecules can bind with the active site. Therefore, an enzyme is a sort of biological enzyme catalyst.

Enzymes are classified into several catagories, such as hydrolytic oxidising and reducing depending on the type of reaction they control hydrolytic enzymes accelerate reactions in which a substance is broken down into simpler compounds through reactions with water molecules oxidising enzymes, know as oxidies acceleate oxidation reactions reducing enzymes speed up reduction reactions, in which oxygen is removed.

Catalase is present in the peroxisomes (microbody organelles that have various oxidation reactions in which toxic peroxides are generated as side products) of nearly all aerobic cell so it serves to protect the cell from toxic affects of hydrogen peroxide by catalysing its decomposition into molecular oxygen and water without the production of free radicals (an atom or a group of atoms with an unpaired electron. Radicals are unusually reactive and are capable of causing a wide range of biological damage).

The equation for the reaction that I am going to be looking at is:

Hydrogen Peroxide + Catalase = oxygen and water

Using my information of catalayse, it is clear that one of the products of the reaction is oxygen and therefore to measure the rate reaction, I will measure the rate at which oxygen is produced when hydrogen peroxide is mixed with an enzyme.

Aim: ‘to find out when using the same amount of potatoe and hydrogen peroxide, if changing the area of the potato will affect the rate of the reaction.’

Prediction : I ...

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The equation for the reaction that I am going to be looking at is:

Hydrogen Peroxide + Catalase = oxygen and water

Aim: ‘to find out when using the same amount of potatoe and hydrogen peroxide, if changing the area of the potato will affect the rate of the reaction.’

Prediction : I think when I drop the same amount of potato into the hydrogen peroxide with a larger area the faster the reaction will take place. I think this because the larger the area of the potato the more active sights there are and so the hydrogen peroxide will be able to be broken down at a faster rate.

Preliminary Investigation.

To make sure that the investigation goes how I want it to go I will do a preliminary investigation. So that if any thing goes wrong in the preliminary investigation I will be able to change it and make my result in the investigation more relable.

Apparatus

Patato

Potato boarer
Scalpal
Set of scales
5 test tubes
1 test tube holder (able to hold 5 test tubes)
stop watch
results chart

Diagram

Brief method:

set up equipment
measure 10ml of hydrogen peroxide into each of the two test tubes and place them into the test tube rack
use the potato borer to cut a tube of potato and slice width ways into 1g pieces and weight on the scales to cheeck weight.
Drop each piece of potato into the two test tubes and begin the stopwatch.
Once 5 minutes have passed, stop the stop watch and measure the amount of bubbles produced with a ruler and record your results.

Table of results

Test tube number measure of bubbles produced in (mm)

What I learnt from these trials and how I will modify the method for the extended investigation.

In the extended investigation I am going to modify my experiment so that I can get more reliable results. In the preliminary investigation I had the problem that the oxygen (O2) bubbles which were produced by the reaction between the hydrogen peroxide and potato were bursting. This happened because the bubbles could not stay there for five minutes. I could make the measurement of time shorter so less bubbles would burst but if I did that less bubbles would be produced and it would be harder to measure the amount foamed by the reaction.

So to keep the bubbles there longer I am going to make them more dense by adding 1 ml of washing up liquid into each 10 ml of hydrogen peroxide and so this well make them stronger and last for longer.

In the preliminary investigation I had 2 results and in the extended investigation I will have 5 so that I will be able to get a more reliable average.

Extended Investigation

Apparatus

Potato– one large one
Potato borer – to cut the potato so it hass an equal area
Scalpal – to cut the potato with a clear cut
Set of scales – to weigh the potato, so that they are all of equal weight.
5 single test tubes – 5 fore each experiment
1 test tube rack
Hydrogen peroxide 250ml
Washing up liquid 25ml
1 reliable stop watch
Results chart – to record the results clearly

Diagram

Fair test

I will make it as fair as possible by trying to take the most accurate measurement at the most precise times.

I will make sure that the hydrogen peroxide, washing up liquid and potatoe are all measured out to there correct measurment for a each experiment.

I will need an accurate timer as I will be using it to time my experiment and so keep the experiment length equal.

I will use the same stop watch and person timing the experiment each time to keep it as fair as possibel. So that if some one measures the time with different ways this problem will not occur.

I will make sure that the test tube is clean due to if there is any other chemicals lining the tube it could change the outcome of the experiment. Also after each experiment I will clean out the apparatus that I have used.

I will make sure I have enough results to prove my point I will make five experiments for each size of potato I predict this will be enough to explain what I will discover.

I will use someone else to start my stopwatch as I insert the pieces of potato into the hydrogen peroxide and washing up liquid solution.

For my conclusion to be fair and accurate, my results will have to be reliable and sufficient, reliable is not some thing that I can guarantee, but sufficient is something that I can try to do.

Safty

Safty issues that I will need to consider.

I will wear safty glasses to protect my eyes from any accident that may occur.

I will check the apparatus for any broken pieces, that way I can avoid injury to myself or avoid a mistake in my experiment through a leak.
If I do cut myself or drop a piece of experiment I will tell the teacher immediately and get the nurse if necsassary. To avoid this happening I will be careful around glass ware, and walk carefully.

With the scalpal I shall place the safty cover on it when I am not using it. If any hydrogen peroxide is split on my skin I will tell the teacher and place my arm under a ‘cold’ running tap.
If any hydrogen peroxide is spilt on a surface I will let the teacher now immediately and it will be cleared up immediatly.

Method

Clear all equipment out througly and wear safety goggles.
Set up equipment.
Measure out 10ml of hydrogen peroxid H O int 5 single test tubes.
Into each test tube syringe 1ml of washing up liquid into each of the 5 single test tubes. Now in each test tube there is a solution of 10ml H O and 1ml of washing up liquide.
Use the potato borer to cut a cyl;inder of potatoe 1cm in diameter and cut width way’s into 1gram pieces. Place each one on the set of scales to ckeak there weight is correct. If it is heavy use the scalpal to slice a little piece off the end until it is the correct weight.
Drop one piece of potatoe back into each test tube and get someone to begin the stop watch.
After 5 minutes measure the amount of bubbles produced with a ruler and record the results and take the average.
Clean out all the equipment so it is ready for the next experiment.
Repeat for each set of 5 results. But for each set cut the potato into another section, this will increase the area of the potato and still keep the same weight of 1 gram, keep the same amount of hydrogen peroxide and washing up luquid.

Conclusion:

In my prediction I predicted that the larger surface area the potato had the faster the reaction would take place. My graph shows that my prediction was correct.

Each time I increased the surface area of the potato the reaction happened at a greater rate. In the last set of experiment I had an enomylase results there was not an exspected amount of foam produced. This could have been due to incorrect measurements of maybe I did not clean out the test tube properly as well as I did with the others.

When the potatoe was in one piece the average amount of foam produced was 16.4mm and each time I cut the potato the reaction happened faster, this was because the area was increased. The graph shows this because the average line goes up steadily. I think this happened because each time I increased the suface area I increased the amount of active sites. And the more active sites there are the particles of hydrogen peroxide collide with the potatoe and this happens faster because there is more area for this to happen.

The line on the graph goes up at a steady rate and if I was to take the investigation further I could cut the poatao into more slices and see if there is an optimum amount of times that the potato can be sliced into and the amount of foam produced does not increase.

Evaluation

I think my investigation went well, but there are a few things that I know know I would change. I think that maybe I would of used a large piece of potato because I found that a 1g piece of potato was very small and to cut it up into 5 equal pieces made this had. I had to stop cutting the potato up to increase the area because I could not cut up the potato into any more parts. Eg 6 equal parts.

I think I would also increase the amount of washing up liquid from 1g to 2g because some of the bubbles were still bursting. And this would make the bubbles stronger and more dense.

The fact that they were still bursting means that the final results and conclusion would not of been so reliable and so to make it more reliable I could also measure the amount of oxygen produced in a different way.

Diagram

This would stop any of the oxygen produced from escaping and would make my results accurate as the possibility could be to extend my investigation I could see what else affects the rate of reaction such as the temperture and if there is an optimum temperture.

The method went well and no spillages or breakages happened during the experiment. If I were to do the experiments again I would cut the potato into more pieces to see if there was a point at which the area stopped affecting the reaction.