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How Does the Size of Particle Affect the Rate of a Chemical

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Kyle Berkhout

on 1 September 2014

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Transcript of How Does the Size of Particle Affect the Rate of a Chemical

Reactions
Variables
How Does the Size of Particle Affect the Rate of a Chemical Reaction?
By Kyle Berkhout, Tanmay Kulkarni and Bailey Devine-Scott
Aim and Hypothesis
Chemical Reaction
A process that transforms a set of chemical substances to a new one.

Traditional chemical reactions involve the positions of the electrons forming different chemical bonds between atoms.
Physical Reaction
The changing in the state of the matter.

No new chemicals are made, so the effect can be reversed.

Some examples of a physical reaction are melting, freezing, evaporation etc.

Aim
To discover if the size of a tablet affects the rate at which it dissolves
Hypothesis
We believe that the larger the particle the slower the rate of the chemical reaction will be. This is because the larger particle has a small surface area in relation to its volume which will decrease the rate of the chemical reaction.
Independent
The size of the particles (whether it is crushed, halved or whole) That affects and changes the surface area of the tablet.
Scientific Diagram
Method
Observations
Results
Graph
Dependent
The dependent variable is the rate at which the chemical reaction takes place.
Controlled
The controlled variables are the equipment used, same brand of tablet, same amount of water, same temperature.
Full Tablet
30 sec. water’s reacting with the tablet and the reaction seems to be that the water is turning blue
45- water bubbling a bit
1min- blue and a bit bubbling
2 min- still a lot to go, going very slowly.
4min- bubble is getting larger, water getting more dark blue
5min- almost done, just a bit to go
6min- still almost done
7 min- film of white bubbles
7min. 30 almost stopped bubbling
7min 49- first one finished
Half Tablet
1min- water really dark blue
1min 30. both halves are getting smaller
2min. still bubbling, but it’s getting slower
3min. waters really dark blue
4min. still
5min. 1 half is almost done but the other one’s still got a while to go
7min- 1 half’s done, the other is almost done.
8min. 43sec- finished
the tablet floats in water; it rises and sinks again and again
Crushed Tablet
No. 1
The bubbles are spread out while with the full one, it was mainly concentrated in one place
2min- really dark
3min 30sec- bubbling almost stopped
4.04- completely stopped/finished
No.2
30 sec- bubbling near the bottom,there’s stuff at the top
1.30- almost done
2.21- finish
No. 3
1min. bubbling just a bit
2min. almost finished
2min. 54- finished
Discussion/Evaluation
There was no problem with the equipment, no faults or anything, but the way we executed the experiment was incorrect. That’s why we obtained the results that we did. Our results varied for all three types of tablets; whole, halved and crushed. Sometimes the half tablet took longer to dissolve than our whole one. The times of our whole tablet varied from 7 minutes 49 sec to 11min 22sec. Our half tablets dissolving varied from 6min 50sec to 11min 20sec. And our crushed tablet varied from 4min 4sec to 2min 21sec. This clearly suggests that our results were not taken properly. There was a complication in the experiment however.
Discussion/Evaluation
It was particularly difficult to see when the tablet had completely dissolved. This problem may have affected our results and caused our results to be inconclusive. To fix this problem, we could’ve possibly observed a bit better. Another problem we faced was the size of the tablets. We didn’t cut them exactly in half. This could’ve affected the rate of the reaction. One way to fix this problem would have been to accurately measure the tablet and cut it in half with a sharp knife. There were also a few errors that occurred to us during the experiment. These include: parallax error and reaction time. We couldn’t tell exactly how much water was in the beaker (parallax error) and we also couldn’t react as soon as the tablet dissolved completely.
Conclusion
In conclusion, our aim was achieved and our hypothesis was correct. The larger tablets did take longer to dissolve while the crushed tablets dissolved much faster, however we could have performed the experiment more accurately. This proves the fact that the larger the particle, the longer it takes to react.
Equipment
9x Alka-Seltzer tablets
1x Mortar and pestle
3x stopwatch
3x beaker
9x 200ml water
Method
1. Put one whole tablet in 200 mL of water in a beaker.
2. Time how long it takes for the tablet to dissolve.
3. Repeat step 1 and 2 but in another beaker and at the same time
4. Cut one tablet into half and put both halves in 200 mL of water in another beaker.
5. Time how long it takes for the tablet to dissolve.
6. Repeat step 4 and 5 to put a half tablet in three different beakers
Method
7. Crush a whole tablet and put in another beaker filled with 200mL of water.
8. Time how long it takes for the tablet to dissolve.
9. Repeat step 7 and 8 to put a crushed tablet in three different beakers
10. Repeat experiment two more times to get an average and a more accurate result.
11. Record your results in a table and convert into a graph.
Discussion/Evaluation
We couldn’t fix these problems because they were errors, they were bound to happen.Our method worked quite well and having 3 beakers saved us time. Without the use of three beakers at a time, we would have run out of time and would have finished with uncompleted results. The beakers were quite big too, in relation to the other groups’ beakers. But all the beakers we used in our group were the same. This made it a fair test, in terms of the equipment. It would’ve been more reliable though if we would have observed a bit better and could tell when the tablets had completely dissolved. We used three whole tablets, three halved tablets and three crushed tablets to get an average so our results could be more accurate. But because we couldn’t tell exactly when the tablet dissolved, this was quite difficult.
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