Temperature has a large effect on rates of reaction, if you raise the temperature by 10°C approximately the rate of reaction doubles.
Surface area-
As the surface area increases, the rate of reaction increases. This is because when a surface area is large, a greater area of reactant is exposed. This increases the number of particles in the area that has been exposed, therefore number of collisions increase, which leads to a faster reaction.
Concentration-
Increasing the concentration of reactants increases the chances of collisions between reactant molecules. In other words, increasing concentration increases the number of collisions between molecules. As you increase the concentration of an acid, there are more acid particles in the same volume. Therefore there is a greater chance of acid particles colliding, and reacting with particle on the surface of the marble chip. Therefore the rate of reaction increases.
Catalysts-
A catalyst is a substance that speeds up chemical reactions. At the end of the reaction, the catalyst is chemically unchanged. When catalysts are present the chances of reaction increase even if the particles don’t have enough energy. This is due to catalysts making reactions speed up, as one particle is fixed to the surface.
Final Prediction-
Looking at all the information I have found on factors affecting the rate of reaction, I can make a final prediction. I predict as the temperature of hydrochloric acid increases the rate of reaction will increase. If I decrease the temperature of the acid the rate of reaction will decrease. The more heat given off to the matter, the more energetic the particles get which results to faster movement and more frequent collisions. This is called the ‘collision theory’. Collision theory is when particles that move at different speeds collide with each other. In collision theory for a reaction to take place the particles must collide with each other and also the must have sufficient energy for a product to be produced. I predict that the particles in the marble chips receive more energy and then start colliding with each other to increase the reaction, the rate simply depends on how hard and often the particles collide with each other. Therefore by using all my knowledge, my secondary resources and my past work on chemical reactions I have been able to make a sensible and reliable prediction. My final prediction is as I increase the temperature of hydrochloric acid the rate of reaction will increase. From what I know I can make a quantitative prediction, my highest temperature 30°C will produce the most amount of gas in the least time. In other words the reaction with acid at 30°C will be the fastest reaction.
Below is what I think my graph will look like:
Preliminary Experiment-
Before planning or starting to do my final experiment for my investigation, I have prepared a pilot test (preliminary experiment). With my pilot test I was investigating how temperature of hydrochloric acid affects its rate of reaction with calcium carbonate. I carried out two temperatures, 10°C and room temperature (25°C).
Apparatus-
- Hydrochloric acid
- 30 marble chips
- Gas Syringe
- Ice
- Thermometer
- Glass beaker
- Conical flask
- Stop watch
- Clamp
- Safety goggles
- Measuring cylinder
Method (preliminary experiment)
- I collected all my apparatus and set it out appropriately on the workbench.
- Set my experiment up and made sure all my equipment was clean.
- I measured 20ml of acid and poured it into my glass beaker.
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I made sure it was at correct temperature by using a thermometer, to make the acid go down to 10°C I used the ice.
- I added 15 marble chips in a conical flask and poured the acid in.
- I then started my stopwatch, and every 10 seconds I took results.
- I repeated the same process for room temperature.
By carrying out this pilot test, I know what to do in the actual experiment and not make the same mistakes. I noticed that 20cm³ of acid wasn’t enough for my experiment to work properly so I instead I will use 30cm³ of acid in my final experiment. I also found out that 15 marble chips is too much for my experiment so I will reduce it to 10 marble chips. My results were not reliable or sensible, but now I know what to improve in my actual experiment.
Method (final experiment)-
Apparatus-
- Hydrochloric acid
- Glass beaker
- Thermometer
- Heat proof mat
- Gauze
- Plastic beaker of ice
- Tripod
- Bunsen burner
- Gas syringe
- Stop watch
- Conical flask
- Measuring cylinder
- Rubber tube (delivery tube)
- Bung
- Pipette
- Clamp stand
- Tongs
- Safety goggles
- Ice crusher
- Splint
- Marble chips
Variables-
The only variable I will be controlling in this experiment is temperature, as I am investigating how temperature affects the rate of reaction. All the other variables I will constantly be keeping the same, I have to make sure the other three variables (surface area, concentration and catalyst) stay constantly the same and do not change to ensure it is a fair test.
I will change the temperature of the acid four times as I am doing four experiments each with different acid temperatures. 1) 15°C hydrochloric acid, 2) 20°C hydrochloric acid, 3) 25°C hydrochloric acid and 4) 30°C hydrochloric acid. I will repeat each experiment three times.
Fair test-
I will ensure my experiment is a fair test by doing the following things:
- Make sure the amount of acid is always the same.
- Make sure when I repeat a certain temperature the temperature of the acid stays the same.
- I will make sure all my apparatus is washed so I am sure that there is no chemicals left behind which will give me inaccurate results.
- I will start my stopwatch immediately as the acid and marble chips are mixed to ensure timing is accurate.
- I will make sure that in every experiment only 10 marble chips are put in the solution.
- I will make sure all my equipment is working properly.
- I will make sure I use the same gas syringe each time I do an experiment, as it will then slide the same each time.
- I will make sure I read the intervals on the gas syringe directly on eye level, so all readings are taken accurately.
- I will make sure I take readings every 10 seconds through out the whole experiment.
Safety precautions-
- Before I start my experiment I will make sure my coat and bag is put away safely away from the workbench to avoid any danger.
- I will constantly wear my safety goggles throughout the whole experiment as acids are involved.
- I will set the experiment up away from the edge of the workbench.
- If any danger is in place with gas/fire I will make sure I go on turn the gas off from the mains.
- I will not keep any equipment near the sink/tap.
- Finally if any spillages are made with acid etc, it will be washed through ally with water.
Method (final experiment)-
- I will clear the workbench and collect all the equipment.
- I will set all the apparatus out on the workbench appropriately.
- Clear things near the workbench, (example-bag).
- I will conduct all my safety procedures.
- I will measure 30cm³ of hydrochloric acid in a measuring cylinder and then more it into a glass beaker.
- With a thermometer I will read the temperature of the acid.
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Depending on the temperature needed I will either heat the acid on a Bunsen burner or cool it in an ice beaker. Room temperature is 25°C so for 15°C and 20°C I will place it in an ice beaker to cool the acid, and for 30°C I will place it on a Bunsen burner to heat the acid.
- I will keep reading the thermometer to make sure the temperature is on level.
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The first temperature I will do is 15°C, so I will put it in an ice beaker to cool.
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I will keep the thermometer inside so I can constantly read the temperature and wait for it to reach 15°C.
- While this is happening I will count 10 marble chips and keep them ready.
- When the acid has reached the correct temperature I will pour the acid into a conical flask and put the 10 marble chips with it.
- I will then seal it immediately with the rubber cork attached on to the gas syringe.
- At the same time I will start my stopwatch.
- Then every 10 seconds I will take readings off the gas syringe.
- For each temperature I will repeat the experiment three times to get accurate and reliable results. I will use the same process each time as well.
This is what my results table will look like:
Below is a diagram of my apparatus:
