JocelynCarolRechenna

Battery Challenge: Amount of Salt
Carol, Rechenna, Jocelyn

Abstract
For this investigation, we set up an experiment that allowed us to measure and change the concentration of salt in tap water and how the amount of salt effects the current and voltage the "salt water battery" would produce. Due to unforseen circumstances, instead of adding different amounts of salt, we diluted the solution each time. We now conclude that salt does not really effect the amount of voltage/current that gets generated.

Introduction
The purpose of this experiment was to find out if the amount of salt effects the amount of voltage and current a "salt water battery" would make. The independent variable we are investigating is the amount of salt in normal, unchanged tap water. We expected that the amount of salt will effect the amount of voltage and current the "salt water battery" would generate. We thought that if there is more salt, then the voltage and current would increase. We expected a graph somewhat like this:



Materials
Iron (4.1 by 5.5) Copper (5.5 by 4.5) Plastic cup 200+ beaker Salt Meter, wires Digital balance Thermometer

1. Measure the weight of the empty beaker on the digital balance. (10.02 g) 2. Put salt into the empty cup, the total weight as 15.02 g. This means the amount of salt is 5 g. 3. Get a beaker, and fill it with 200 ml of tap water. 4. Put the thermometer inside tap water. Record temperature. 5. Put the 200 ml of tap water into the cup, add the 5 g of salt. 6. Stir for 30 seconds, allowing the salt to dissolve. 7. Cut/sharpen/perfect one piece of copper, and one piece of iron. Make sure that they are in the same size. 8. Place the metal on the inside of the cup, one on each side. Tape the metals to the side of the cup. 9. Connect the wires onto the copper, and connect the probe from the meter onto the clips. (make sure it's turned off) 10. Spin dial. Wait for 15 seconds. Record voltage. 11. Spin dial. Wait for 15 seconds. Record current. 11. Redo experiment, without removing the metals from the cup, same amount of water, same water temperature, but add 10g of salt this time. (Experiment 12. Pour out 50mL of your solution (with 10g of salt and 200 ml of water), and add another 150mL of tap water. This would become 1/4th of the previous experiment. We are trying to dilute the solution. 13. When you're done with step 12, turn the probe to V2 (voltage)-counterclockwise and count to 15 seconds to get the voltage of the experiment. Do the same with current but turn it off first, wait for a few seconds and turn it clockwise to Amp2. 14. Redo step 12 and 13. until you finish all 5 experiments so you have both current and voltage.
 * //**Pay close attention! This part gets tricky...**//


 * This is making the water dilute each time. 200/4 = 50, so basically you take 1/4 of 10g of salt, when you find the answer, take the answer and divide it by four each time. 10/4= 2.5 --> ans/4= .625 --> ...and so on..*

Data
1st experiment Salt: 5g Current: - Voltage: .33

2nd experiment Salt: 10g Current: 1.25 Voltage: .205

3rd experiment In the 3rd experiment we did something different to speed up the process. We toke out 10g of 50ml so that is ¼ of 200ml, so now we have 2 ½ grams of salt. Current: 1.47 Voltage: 2.80

4th experiment We continued with the process of speeding things up. Salt: .625g Current: 1.8 (after 15 sec) Voltage: .395 (after 15 sec)

5th experiment 50 ml of the original solution Salt: .15625 g Current: 0.148 Voltage: 1.497 This is our table:
 * # # of Experiment || amount of salt (g) || +/- || Voltage (v) || Current (amp) ||
 * experiment #1 || 5 || 0.01 || - || - ||
 * experiment #2 || 10 || 0.01 || 0.205 || 1.25 ||
 * experiment #3 || 2.50 || 0.01 || 2.8 || 1.47 ||
 * experiment #4 || 0.625 || 0.01 || 0.395 || 1.8 ||
 * experiment #5 || 0.16 || 0.01 || 0.418 || 1.497 ||

<-- graphs. (amount of salt+current, amount of salt+voltage, voltage+current for each experiment)

Evaluation
The data was very different from what we had expected. The amount of salt did not have any drastic effect on the voltage and current, and there was no stable change. Due to unforeseen circumstances (some of the copper and iron had dissolved in our previous solution after two days, and changed the entire solution), we had to change our experiment. We changed our original experiment (adding different amounts of salt), to diluting the solution (thus changing the concentration). This change of plans and unexpected solution change made this experiment weak. The strength of this experiment was that we did a good job of keeping the other variables (such as distance between metals, the size of metals, amount of water, temperature of water etc) constant. Possible modifications would be diluting more of the solution so we have a more certain answer to our main question: Does the amount of salt change the current or voltage of a "salt water battery"? Also, we could start with more salt so we can see if there are any drastic changes. If so, how? To improve our investigation, we could also try to repeat the whole experiment to be certain. From our results, we can conclude that the amount of salt we put in tap water will not drastically effect the currents and voltage generated from a "salt water battery". We can conclude that the salt randomly changed the current and voltage. I would recommend to the group that we should have more attempts at this experiment so we can have be absolutely certain that our answer is correct.



The data of our experiment was really different from what we had expected. By adding more salt each time to tap water, we expected that the voltage and current will increase. After the experiment, we had a conclusion of; the amount doesn’t affect the voltage and current, and no stable change. One of the error that caused our whole experiment to change was we left our two metals; copper and iron, in the water for two days, and the salt water caused the rust on the metals to wash off and contaminate the tap water. Because of this, we had to change our experiment, so instead of dumping out the water, we diluted the solution-changing the concentration. The weakness of this experiment was we didn’t know that the salt water will wash off the rust on the metals, which changed our experiment and made a sudden change. The strength of this experiment is even with the sudden change, we still kept the other variables the same; temperature of water, amount of water, distance between the metals, size of the metals. Does the amount of salt change the current or voltage of a "salt water battery"? The best way for this experiment to answer our question is that if we knew there would be a sudden change, we can start off with more salt dissolved in the tap water, and dilute it each time. The answer that we have concluded from our experiment is that the amount of salt isn’t the big cause or main reason for the voltage and current to have a big difference. I think in order for this experiment to answer our question, we should do it again, and this time, add more salt and then dilute it. ---

In my opinion I think our experiment went perfect, even though there were some changes and errors. With our first attempt in the experiment we made a little error with letting the metals seat in the salt water for 3 days, So that began to rust, even though we made an error we learned from it and gained experience. So to fasten up the experiment we added more salt to the tap water and diluted it. So overall the amount of salt didn’t have a huge impact on the voltage and current. For the future I believe we should have more attempt s till we are absoultly sure that we have the correct data and results.