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rate of reaction

Free essay example:

                                                                        Katie Whitmore 10H

Year 10 coursework                                                         

Investigate how concentration affects the rate of reaction

What is meant by rate of reaction?

Chemical reactions can take place at different speeds. An explosion, such as the reaction of hydrogen and oxygen together to produce water vapour, is a very fast reaction – it is over in a tiny fraction of a second. The rusting of iron and the souring of milk are very slow reactions.

A reaction which is over in a fraction of a second is a very fast reaction. We say it has a high rate of reaction. As the time taken for the reaction to be completed increases, the rate of reaction decreases.

What factors affect the rate of reaction?

The effect of increasing concentration on the rate of reaction is relatively easy to predict qualitatively. It is not possible to be sure of a quantitive relationship without carrying out experimental studies. In some cases doubling the concentration of one of the reactants doubles the rate of reaction. However, it is possible to find reactions where increasing the concentration of one of the reactants has no effect at all on the rate of reaction.

Which factor are you investigating?

Rate of reaction is how fast or slow the rate of reaction is. The factors that affect the rate of reaction are tempreture, concentration, pressure and light. I am investigating concentration, the reaction between sodium thiosulphate and hydrochloric acid. I am measuring how long it takes for the solution to go cloudy.

Equipment –

  • Sodium thiosulphate solution
  • Dilate hydrochloric acid
  • Large measuring cylinder
  • Small measuring cylinder
  • Conical flask
  • Scrap piece of paper
  • Stop clock
  • Science goggles

How are you going to make your investigation safe?

Method –

Carefully measure out 50cm³ of sodium thiosulphate.

Pour it into the conical flask.

Draw a cross on a scrap piece of paper, put the flask over the top of the cross.

If you look down through the top of the flask you should be able to see the cross clearly.

Carefully measure out 5cm³ dilate hydrochloric acid, pour it into the flask containing the sodium thiosulphate solution.

Start the stop clock.

Look down at the cross, the solution will turn cloudy.

Time how long it takes for the cross to disappear.

Pour the solution away.

Repeat the experiment twice and work out the mean time for the cross to disappear.

How are you going to make your investigation fair?

I will make the investigation fair by repeating the experiment, when repeating keep the measurements the same.

This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.

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Here's what a star student thought of this essay

3 star(s)

Response to the question

Uses different text sizes in the experiment which should be made uniform as this looks untidy. Uses the concept of a 'fair' experiment which is very basic terminology. The student overall presents a simplistic style essay which is accurate but ...

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Response to the question

Uses different text sizes in the experiment which should be made uniform as this looks untidy. Uses the concept of a 'fair' experiment which is very basic terminology. The student overall presents a simplistic style essay which is accurate but basic in understanding. The results are not included in this essay, neither is an assessment of the results. The student should use solid scientific evidence to make a prediction.

Level of analysis

The rate of reaction is explained well and clearly for this level of student, but to gain higher marks the student could have researched the theoretical actual chemical definition of rate and what this means. In the cases of where the student mentions that doubling the rate of reaction doubles the rate of reaction, the student should give examples of where this is the instance, and then again when they say this is not sometimes the case. The student chooses a poor method to assess the rate of reaction. Measuring how 'cloudy' the experiment is means that the margin for error is great as this will vary from person to person.

Quality of writing

Communicates in a clear and simplistic way so the writing is easy to understand. Grammar, punctuation and spelling are all correct.


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Reviewed by skatealexia 27/06/2012

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