Method 2:
I will pour 80ml of saturated salt water into a measuring cylinder, to get the right amount of liquid, and then I will pour that into a beaker. After, I will set up the voltmeter and connect the metals to the crocodile clips. I then need to pair up two metals and write down their result. Once again I will need to repeat this with the other metals until 15 results show.
Next I will need to find out the best combinations and find out if diluting the solution will change the results.
To dilute I need to put a certain amount of acid and a certain amount of water in the beaker.
For example: - If I wanted my solution half diluted I would pour 40ml of hydrochloric acid and 40ml of water.
In this experiment I diluted the solution 9 times, from 0ml – 80ml.
Prediction:
I predict that carbon and any other metal will create the highest voltage. I predict this because carbon is the only non-metal, so it’s harder for it to dissolve in the solution, especially hydrochloric acid. It is fairly reactive in the reactivity series and is the second reactive metal out of the five metals.
Fair test:
So as this experiment is fair, I need to:
- Keep the same amount of solution in both beakers, because if I do this I’m changing the variable and the experiment might vary at different amounts of solution.
- Keep to the same voltmeter, this is because some voltmeters may be weaker than others.
- Repeat the experiment 3 times, so if anything goes wrong you have two other results to back you up.
Health and safety:
I know that in this experiment acid is used. Acid can be very dangerous, if not taken seriously, so I need to make sure that during this experiment I wear safety glasses to protect my eyes. Also glass is involved in the experiment, meaning I need to be cautious with these apparatus, if I’m not cautious I may drop the glass on the floor and find that the glass has smashed, the glass may even cut or scar me.
Results:
After pairing up the metals three times and giving the result an average, here were the results:
Hydrochloric acid:
The best combined metals in hydrochloric acid was zinc and Carbon. To further this experiment on, I diluted the solution and measured the voltage of zinc and carbon.
Here are the results:
The result above shows that when I diluted the hydrochloric acid with water, the voltage decreased each time more water was added.
Saturated Salt Solution:
The best combination in saturated salt solution, is zinc and carbon again. The results below show what happens when the solution is diluted.
When the solution was half diluted, it came up with a bit more of a higher voltage then when it had no water in the solution at.
Conclusion from graph:
In Graph 1:
The pattern in this graph increases steadily, until no water is used and then the pattern drops rapidly, this shows that when I diluted the hydrochloric acid with water, the voltage became higher each time. In the line of best fit, I missed out the last result as that too dropped rapidly. But I can understand why it did drop. There was a rapid drop because there was not any water in the solution.
In graph 2:
The pattern in this graph was all over the place, it showed that when I diluted the salt solution, the voltage was either high or low, and was hardly ever average. In the line of best fit, I miss out most of the results, because I think the line was going up and down too rapidly. These problems may have occurred because of unfair testing.
Conclusion:
The best combination was zinc and carbon in half-diluted saturated salt solution.
The second best combination was carbon and zinc, again, in 1mola of hydrochloric acid. Carbon and zinc had the best voltage because they were the both fairly reactive towards acids and water.
The results compared to my prediction were correct, I knew that carbon would create the highest voltage, due to its position in the reactivity series. The reason zinc produced the highest voltage, with carbon, is because it’s almost as reactive as carbon.
Evaluation:
The experiment wasn’t a very accurate experiment. One reason is because it was fairly hard to write down a correct result. Reading from the voltmeter was very difficult as it never stopped on a proper result, the result just increased and then decreased. I would Also there was a lack of metals, so with the metals I did have I had to recycle them, and some of them dissolved slightly, meaning that there were not as many particles inside.
To improve this procedure I would:
- Use more metals, so I get a wider range of combinations.
- Repeat diluting the solution at least 5 times to get an accurate average.
- Include some more solutions, e.g 2molas of hydrochloric acid. To give me a wider range of solutions, and their voltages.
- Leave the voltmeter for 10 sec’s and then write down the results.