The collision theory model explains why smaller particles have a faster reaction
Temperature
Lower energy therefore particles move slowly so a slow reaction
More energy therefore particles move faster so more collisions, so faster reaction
The collision theory explains that increasing temperature makes reactions faster.
Concentration
Concentration measures how many moles per 1000cm3
KEY
1mole=6 x 1023 particles
1 Litre= 1dm→1000cm3
1dm x 1dm x 1dm= 1cm3
Diluted →
( 1 mole/litre)
(1 mole/dm3)
More concentrated so 2 moles/dm3→
So there are two times as many particles in the same place, therefore more collisions, so a faster reaction.
If we double the concentration, there are twice as many particles in the same space, so therefore twice as many collisions so faster reactions.
Catalysts
Catalysts provide an alternative path to reaction with lower activation energy.
Prediction
In this experiment my prediction is that the cross will disappear faster as the temperature gets warmer. This is because as it gets warmer, the atoms vibrate more and move around quicker. This means that when it mixed with the sodium atoms, they hit each other atoms faster and harder which in result is forcing the reaction to happen quicker. When the temperature is lowered the opposite occurs because the atoms have less energy and would hit less hard and fast so it would take a longer period of time to get the same result. My prediction of how the graph would look like is this:
The graph begins to go down because at certain temperatures as the atoms get more energy and hit more making the cross seem to disappear faster. A theory, which links into this experiment, is the collision theory. This is because the collision theory deals with atoms vibrating as they receive more energy and they then hit more often.
Apparatus
- 1 thermometer
- 1 beaker
- 2 measuring cylinders
- 1 conical flask
- 1 tripod
- 1 gauze
- 1 heatproof mat
- 1 stopwatch
- 1 Bunsen burner
- X board
- 1 pair of tongs
- 1 pair of goggles
Method
- Measure 10ml of hydrochloric acid into conical flask
- Heat over Bunsen burner until desired heat
- Remove immediately and place on top of hand-drawn flask
- Add 25ml of Sodium thiosulphate
- Time to see how long the cross takes to disappear completely
- Repeat 3 times
- Rinse and repeat to the heat 5 º over the last temperature.
Safety
A pair of goggles will be worn during the heating part of the experiment in order to protect the eyes. When handling hot beakers and measuring cylinders a pair of tongs will be used. A gauze and heatproof mat will be used while heating to avoid any damage to the equipment.
Recording
Fair Test
In order for my results to be valid the experiment must be a fair one. I will use the same judgement each time for trying to see when the X has disappeared. I will make sure that the measuring cylinders for the HCl and thiosulphate will not be mixed up. The amount of HCl will be the same each time, and the amount of thiosulphate will be fixed at 15 cm3. During the heating stage of the experiment, a blue flame will be used throughout. Also the same Bunsen burner and gas tap will be used to maintain continuity. All of these precautions will make my final results more reliable and keep anomalies at a minimum so thus make the entire investigation more successful. The only change that will happen will be that the temperature of the Hydrochloric acid will go up 5 º every three times
ANALYSIS
Results
From my results I can conclude that as the temperature of the hydrochloric acid rises, the rate for reaction also gets higher. This is in line with the collision theory, which defines that as the acid get hotter, the atoms get more energy and vibrate more. When the two liquids hit, the atoms are pushed together and because they are vibrating more they hit faster and harder therefore causing the reaction to speed up and the solution to turn a yellow colour quicker so the cross seems to disappear quicker. The graph proves that the theory works for this experiment, as it is a curved line. The sketch graph I drew in my prediction matched the real graph showing that the science I used to explain my prediction was correct.
Evaluation
Looking at my results I can say that they were quite reliable and accurate. I had one anomalous result even after an average over three measurements. This was at 30º and I think may have been because the water we rinsed the beaker out in may have stayed in and caused the reaction to slow down. I can say that looking at my results when I repeated results they were quite close together. I think that I did the experiment quite well although I found it hard to spot where the exact moment when the cross disappeared. This is why we did an average over 3 measurements.
To improve the experiment I would need to have a very accurate stopwatch to time exactly how long the cross took to dissappear so I could be really precise in my results. Ways in which I could extend this experiment are to use a different size of cross so that it doesn't disappear at such a low temperature this way I could carry on to see whether the collision theory is still right at higher temperatures.