Hypothesis – I predict that the smaller marble chips will give tha largest range of results, ie. the best results, because the smaller marble chips have a much larger surface area overall. The larger surface area means the more particles exposed and therefore the largest range of results and the best results for the main investigation.
Method –
Equipment – Gas syringe
Conical Flask
Bung
Small/ medium/ large marble chips
Hydrochloric acid
Distilled water
Measuring cylinders
Clamp
Bosses
Clamp stand
Stopclock
- Set up apparatus as shown.
- Using the measuring cylinders, measure correct amounts of hydrochloric acid and distilled water. Using the concentrations :
3. Pour the correct amounts into the conical flask.
4. Drop the small marble chips into the conical flask, push in the bung and start the stopclock as quickly as possible.
5. When the stopclock has reached one minute measure the amount of gas that has been collected in the gas syring. Record the results.
6. Repeat this three times for each set of concentrations.
Results –
Graphs –
Conclusion – We have decided to use small marble chips in our main experiment. We have decided this because of the results that we can see from our preliminary experiment. They seem to have the largest range and therefore the best results. We can also see from this experiment that the larger the marble chips the less gas there was after one minute, so the larger the marble chip the longer time it takes for the gas syringe to fill, ie, the slower the rate of the reaction. This is because the larger the surface area, the more particles are present to react and the more particles that are present to react, the more succesful collisions will occur and therefore the faster the rate of the reaction. So if the surface area is smaller the reaction will take longer. Also we can see from this preliminary experiment that the larger the percentage of hydrochloric acid the longer time it takes for the gas syringe to fill up.
Planning –
Variables – There are a variety of different independent and dependent variables that we could use for this experience. The different independent variables I could chose from include: the size of the marble chips, ie. Surface area – this would affect the rate of reaction because the larger the surface area the larger number of particles are exposed. The larger number of particles exposed means the more particles are present to react, which means a higher number of succesful collisions which means the rate of reaction will be faster. Another independent variable that I could choose could be the temperature of the investigation. This would affect the rate of reaction because the temperature of a reaction is the measure of the average kinetic energy of the particles. Therefore, this means that the higher the temperature, the higher the average kinetic energy of the particles which means the higher number of succesful collisions can occur because of the energy of the particles. The higher number of succesful collisions means that the rate of reaction will increase. The last independent variable I could choose could be concentration, this would affect the rate of reaction because: the higher the concentration of the liquid the higher the number of particles present. The higher the number of particles present the higher the number of succesful collisions will be. Which therefore means that the rate of reaction will be faster.
The variety of different dependant variables I could choose from are the volume of gas in the gas syringe at a set time, the volume of gas in the gas syringe measured at equal intervals, the time once a set volume of gas has been measured in the gas syring and the mass loss of the marble chips after the experiment.
I have chosen to use the concentration of the hydrochloric acid for my independent variable and the volume of gas in the gas syringe at a set time for my dependant variable. We have chosen to use this dependant variable because for practical reasons the other variables would not be possible, such as not enough top-pan balnaces etc.
Fair Test – There are many ways that this test could be made a fair test, however, unfortunately not all of them were used while doing the actual experiment and I shall talk about this later on in how I could improve the experiment. Ways that would make this experiment a fair test include: Making sure that the same equipment/apparatus is used each time the experiment is re-done so that we can be sure that it is an complete fair test. Also, by makings sure that each set of marble chips (small, medium and large) all weigh exactly the same amount when used in the experiment. Also, by keeping the conditions of where the experiment take place, such as temperature, are kept the same for each repeat to be sure of accurate results.
Main Method –
Equipment – Gas syringe
Conical Flask
Bung
Small/ medium/ large marble chips
Hydrochloric acid
Distilled water
Measuring cylinders
Clamp
Bosses
Clamp stand
Stopclock
- Set up apparatus as shown.
- Using the measuring cylinders, measure correct amounts of hydrochloric acid and distilled water. Using the concentrations :
3. Pour the correct amounts into the conical flask.
4. Drop the marble chips into the conical flask, push in the bung and start the stopclock as quickly as possible.
5. When the stopclock has reached one minute measure the amount of gas that has been collected in the gas syring. Record the results.
6. Repeat this three times for each set of concentrations and different size of marble chips.
Results –
Graphs –
Conclusion – From my results I can see that the higher the concentration of hydrochloric acid the faster the rate of reaction. I can see this because when the concentration of hydrochloric acid was at 40% the rate was 0.35, at 50% it was 0.5833, at 60% it was 0.6216, at 50% it was 0.9833 and at 100% it was 1.3. I can see from this that as the concentration is increased the rate of reaction increases with it. I can see from my graph that the concentration and the rate of reaction are nearly directly proportional because they increase together in nearly a straight line.
This happens because of the collision theory. The collision theory states that when there are more particles present in a colution the more succesful collisions are likely to occur. Therefore, due to this the quicker the reaction will take place and therefore the faster the rate of the reaction will be.
My results do match my hypothesis because in my hypothesis I predicted that the higher the concentration of the hydrochloric acid, the faster the rate of the reaction and that is what happened.
Evaluation –
