- 100ml beaker
- 1 cm magnesium pieces
- Pipette
- Measuring cylinder
- Stop clock
- Hydrochloric acid
- Water
- Goggles
- Paper clip
Method
- Cut the magnesium to pieces of 1cm.
- Measure the hydrochloric acid to water concentration.
- Clean beaker.
- Put the solution of water and acid into the beaker.
- Put a piece of magnesium into a paper clip.
- Add the magnesium and
- Start the stop clock.
- Watch it until all the magnesium has gone.
- Stop the clock and record the time.
- Fine-tune my concentration of acid to water to something like 5.5:4.5 to get closer to the needed time value.
Fair test
My independent variable will be the concentration of acid to water.
My dependent variable will be the time.
Factors I will keep the same are the size of the magnesium, purity of magnesium, beaker and stop clock.
Results
Range
10ml acid: 0ml water- 1ml acid: 9ml water
Interval
10:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9
Precision
We will measure all our results to the nearest 10th of a ml.
Reliable
We will repeat each experiment twice and then find the average.
Accurate
It will be accurate if they are similar results and if the averages go down as the concentration of acid to water decreases.
Analysis
My line of best fit is a curve, and it shows a negative correlation, which is what we expected because we said as the concentration of acid to water, goes down, the time goes up.
I think we got the results we did because we carried the experiment out over 2 lessons and used a paper clip to keep the magnesium fully covered by acid, this may have affected results because the aluminium in the paper clip may have reacted slightly with the acid, but as it was aluminium, it is not expected to have reacted much. Although I planned to carry it all out in one lessons, we were not able to. We also did not have time to carry out experiments on all the concentrations, if we had, we may have found a more visible pattern.
My prediction was correct as I said the time would decrease as the concentration increased.
Evaluation
There are no very odd results in my table but there are 2 results that are just off, but are not too far off. I think that they are slightly off because when we were doing the experiment we did those values the next lesson, so we may have used different beakers and different batches of magnesium and hydrochloric acid.
I did each experiment twice and then found the averages, most of my results were quite similar except for, when we did 4 acid: 6 water, the first value was 68 seconds and the second was 143 seconds.
To make the experiment better, we could have used a burette to get more accurate measurements of water and acid, we could also have used a balance to weigh the mixture until it loses all the magnesium.
We carried out a preliminary experiment and our findings in that were quite similar to the results in our actual exam, seeing as the sizes of magnesium wire varied in each experiment.
