Effect of Surface Area in an Experiment

Title: The effect of surface area in an experiment.

Chosen factor: effects of surface area

Chosen experiment: Calcium carbonate and Hydrochloric acid (option 2)

Questions:

• Will increasing the surface area of the calcium carbonate slow down the reaction rate?
• How do you increase the surface are of Calcium Carbonate?
• Will increasing the surface are of Calcium Carbonate speed up the reaction rate?
• Will the smaller surface area Calcium carbonate have a faster reaction rate than the larger surface area Calcium carbonate?

Background Information:

• What is a reaction rate?

A reaction rate is the rate in which a chemical reaction occurs. (Britannica.com, 2017)

The reaction rate can be increased by increasing the surface area (crushed material). For example, in custard powder factories, there is a high rate of the custard powder exploding, because of the larger surface area. This happens because the finer the substance is crushed, more particles are exposed to the other substance in the experiment (BBC,2014) To increase surface area, the material needs to be crushed into a powder. For less surface area, the material needs to stay in a big clump.

Diagram sourced off (BBC, 2014)

This diagram shows the reaction rate of a greater surface area (blue) is much faster than the smaller surface area (red). The finer a substance is, generally, the faster the reaction rate will be. The larger surface area can also act as a Catalyst. (chemguide,2013)

Collision theory is a theory based off particles of elements colliding together, which creates a chemical reaction. Any collisions without enough energy won’t produce a reaction. For a reaction to occur, there must be energy within the atom which will cause them to collide together to create a chemical reaction. (BBC,2014)

• Calcium Carbonate and Hydrochloric acid:

In the experiment the Calcium Carbonate will be crushed, then combined with the hydrochloric acid. Alongside the crushed calcium carbonate will be two other different grades of Calcium Carbonate which will have a lower surface area to each other. The different grade’s reaction times will be compared to each other in 3 different experiments.

• Experiment formula:

calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water

CaCo³ + 2HCI CaCl² + H2O + CO² (Chemguide, 2013)

Hypothesis:

It is hypothesised that when the surface area is increased, the reaction rate will speed up. When the surface area is decreased the reaction, rate will slow down because, the chemical can only react with the outside of the substance and chew away at it until there is none left, but with an increased surface area there is more atoms to react with compared to a small surface area. The independent variable that will be changed is the surface area of the calcium carbonate (small, medium, large). The dependent variable will be the time of the ration rate in each experiment. The controlled variable will be the amount of calcium carbonate and the amount of hydrochloric acid that is in each experiment.

Method:

Collect all equipment needed for the experiment. Setup experiment, then add 100ml of Hydrochloric acid to each of the beakers. (when adding Hydrochloric acid to the beakers, ensure eyes are at the same level of the beaker to make an accurate measurement. Add all 3 Different grades of Calcium Carbonate to each one of the beakers (make sure Calcium Carbonate is placed in each beaker with care.) Setup should look like this:

Start timer and record results in a table as shown below.

When the reaction completely stopped, all chemicals are tipped into the sink and the sink is washed clean of chemicals. All equipment that has been used is cleaned, and packed into the box. Wet and dry wipe table with disinfectant, ensuring all chemicals have been removed off the surface.

Aim:

The aim of the experiment was to find out if a larger surface are has a faster reaction time than a smaller surface area.

Equipment list:

• Stopwatches (3)
• Calcium Carbonate:
• (large chips, 18g)
• (Small chips, 18g)
• (powder, 18g)
• Hydrochloric acid (270ml) 1M
• Watch glasses (3)
• Spatula
• Measuring cylinder
• Beakers (3)
• Gloves
• Apron
• Goggles

Risk assessment:

Results:

1^st experiment:

2^nd Experiment:

3^rd Experiment:

(Made by Mac Ross on excel)

(Made by Mac Ross on excel)

Discussion:

All results were in seconds’ difference to each other. All experiments had the exact same reaction happen every time. All research that was taken was accurate. The hypothesis which was stated was ‘It is hypothesised that when the surface area is increased, the reaction rate will speed up. When the surface area is decreased the reaction, rate will slow down because, the chemical can only react with the outside of the substance and chew away at it until there is none left, but with an increased surface area there is more atoms to react with compared to a small surface area.’ This hypothesis was supported, because the smaller the surface area was, the faster the reaction happened. Surface area is used in many different scenarios in the world to this day. One of these is in carburetted engines. When fuel goes though the carburettor the fuel gets made into a mist, which is far more explosive than just a drop of fuel. The graphs both show that all of the experiments were very similar. The large surface area experiment when significantly quicker than the other 2. With an average of 1:04 minutes for reaction rate it smashed the other 2. The reaction mainly happened in the first 15 seconds and then slowed down a lot, but it was still fizzing. The other 2 experiments were fizzing the whole time with no increase or decrease in speed with fizzing. The Medium surface area experiment had a misty fizz to it but it wasn’t anywhere near as aggressive as the large surface area experiment. We stopped the experiment at 10 minutes as it was taking too long for the experiment to end, but there was defiantly a decrease in size. The small surface area experiment was a very slow reaction compared to the large surface are reaction. Its bubbles were big and not aggressive at all. We also had to end this experiment at 10 minutes because it was taking too long.

Evaluation:

The Experiments went according to plan, and there were no mishaps. Having 3 experiments going at once saved us a lot of time, and having all of the calcium carbonated crushed up and ready to go also saved us lots of time, which worked well. Not being able to complete the whole reaction for the small and medium surface area reactions was something that didn’t work. Our group went together like peas and carrots. To make the experiment more accurate I would have used a stronger acid, so that we could get a result for each reaction, a bigger working space so that everything wasn’t cluttered, to accurate measuring equipment, so we could improve on the accuracy, and I would have taken better photos to put in the write up so that people can see the layout better. If I was to repeat this experiment again I would use less calcium carbonate and a stronger hydrochloric acid, so that we could get a time for each experiment instead of ending the experiment at 10 minutes. This also would have given us a better understanding of how surface area affects the reaction rate.

Conclusion:

When the surface area is increased between calcium carbonate and hydrochloric acid, the reaction rate is sped up. The hypothesis was supported by the results in the experiment. The results showed that the research and hypothesis were all accurate, and the results were that the larger is surface area is the fast it will react. The small the surface area was, the slower the reaction was, but the experiment did have some mishaps, which can be easily be tweaked to be the perfect experiment. But the experiment was successful in finding the result we were looking for, not only because of chemical reason but because of how our group worked together as well.

Reference list:

Bbc.co.uk. (2017). BBC – GCSE Bitesize: Effect of surface area. [online] Available at: http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/chemical_economics/reaction3rev1.shtml [Accessed 14 Mar. 2017].

Chemguide.co.uk. (2017). The effect of surface area on rates of reaction. [online] Available at: http://www.chemguide.co.uk/physical/basicrates/surfacearea.html [Accessed 14 Mar. 2017].

Chemistry LibreTexts. (2017). Collision Theory. [online] Available at: https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Kinetics/Modeling_Reaction_Kinetics/Collision_Theory [Accessed 14 Mar. 2017].