2) Pressure of gases:
There are more collisions in a given time when you increase the pressure of a gas. In reactions between gases, increasing the pressure will increase the rate of reaction.
3) Temperature of the solution:
Reactions get faster as we raise the temperatures, as there are more cautions in a certain time, because the particles are moving faster and are crashing together harder; so more collisions produce a reaction.
4) Presence of a catalyst:
The energy needed to start a reaction is called its activation energy. A catalyst loves the activation energy. Catalysts make it easier for particles to react, by speeding up a chemical reaction.
5) Surface area or particle size:
Surface area is a measure of how much surface area is exposed, so the more area that is exposed, the more collisions. This is because the particles are ready to react. As we increase the surface area, we increase the rate of reaction.
The key factors that affect rate are:
♦ Concentration
♦ Temperature
♦ Volume
It is only these factors that will effect the experiment that I will be doing in class, which is to investigate the concentration on the rate of reaction.
If you increase the concentration of the acid, you will increase the rate of reaction. If you double the concentration of the acid, you will double the rate of reaction. This implies that however you increase the concentration of the acid, the rate of reaction is increased by the same amount.
Prediction:
I predict that the higher the concentration, the faster the rate of reaction, because the higher the concentration of the solution, the more molecules there are. This means that there will be a higher chance of the molecules colliding with each other and I higher chance of them reaction. This increases the rate of reaction because the concentration is increased.
The rate of reaction begins very rapidly but gradually decreases because the number of molecules present will decrease as they react, because the concentration of the solution decreases. This makes a curve in the graph as the reaction slows down.
The increase in concentration should be directly proportional to the increase of the rate of reaction at a given time.
Fair test:
To make this a fair test we will have to keep all variables the same except the one we area investigating. We will also have to make sure that we carry out the same method more than once to confirm that we get reliable results. To make this experiment an even more reliable and accurate test, I will control the factors that affect the rate of reaction. I will only change one factor at a time or I will not know which factor is affecting the rate. I will keep the rest of factors the same.
The things I will change……………………………………..
Safety:
To ensure that the experiment is safe, I will:
♦ Wear safety goggles.
♦ Keep all stools out of the way when carrying out the experiment.
♦ Keep bags out of the way so no one trips over.
Equipment:
The equipment I will use is drawn and labelled below.
Method:
To make our experiment a fair test, I had to carry out this same method each time. In steps, this is what I did:
- Firstly, put on a pair of safety goggles and add 25cm of dilute hydrochloric acid to the flask.
- Then weigh 5g of marble chips using a piece of paper and a digital balance
- Next, put the flask, marble chips, and a piece of cotton wool on the balance (as shown above), and note the total mass in a results table to two decimal places for accuracy.
- Quickly add the marble chips to the acid and loosely place the cotton wool at the mouth of the flask, trying not to let and carbon dioxide escape.
- Record the mass every thirty seconds until you see that there is no change in mass for three or more readings.
- Repeat steps 1-5 in another experiment to ensure that these results are accurate and reliable.
- Complete your results table and plot graphs to help interpret the results.
Analysing Evidence
We used different concentrations of 1m and 2m and solutions of hydrochloric acid.
Drawing Conclusions
In my experiment, I found out that if I increased the concentration of the solution, the rate of reaction increased, the time it took to react decreased, and more weight was lost. If I doubled the concentration of the solution, the rate of reaction doubled, the time reduced by half, and double the weight was lost.
This theory is proved by my table of results because all throughout the results, I see that in the one molar solution, the weight loss if almost half of the weight losses in the two molar results.
Loss in mass is 0.28g in the 1m solution, but it is 0.61g in the 2m solution. In addition, loss in mass is 0.33g in the 1m solution, but it is 0.70g in the 2m solution. Therefore, as you can see, the weight is almost doubled, every minute.
Throughout the whole experiments, I see that the reaction is always fastest at the start, then slows down in the middle of the experiment, and finally ceases at the end.
This conclusion supports my prediction because at the start of the experiment, I predicted that the higher the concentration, the faster the rate of reaction would be, because the higher the concentration of the solution, the more molecules there are. This means that there will be a higher chance of the molecules colliding with each other and I higher chance of them reaction. This increases the rate of reaction because the concentration is increased.
The rate of reaction begins very rapidly but gradually decreases because the number of molecules present will decrease as they react, because the concentration of the solution decreases. This makes a curve in the graph as the reaction slows down.
The increase in concentration should be directly proportional to the increase of the rate of reaction at a given time.
I understand that my prediction was correct.
