Introduction : Today we will be discussing our experiment we carried out for the research question “What is the effect of different concentrations of Potassium Chloride on electrical conductivity?” In this experiment, our independent variable was the concentrations of KCl (g) and the dependent variable was the electrical conductivity of the water and KCl solution (μS/cm - microSiemens per centimeter). The controlled variables were the temperature of the laboratory, the amount of water used for each solution, the same Ph of water, and the time allowed to measure conductivity (2 minutes). Intro – Jeena Description of Exp – Scott Observations – Jeena Raw Data – Ching Analysis of Data (graph and processed table)– Allison; Applications - Ching Limitations – Jeena and Scott

SCOTT :) Description of experiment: Firstly, we placed 50ml of tap water into 6 eighty ml beakers. We then used an electronic balance to measure the different amounts of KCl, which was 0g, 5g, 10g, 15g, 20g, 25g. We used a weigh boat to make more accurate measurements. We first conducted the controlled experiment where we put the electric probe into the water with 0g of KCl for 2 minutes. To record the data for the conductivity, we connected the Conductivity Probe to the Vernier Lab Pro and then to the computer, and the program we used was Logger Pro. We repeated these steps for the 5 other different concentrations of KCl and then did 3 trials of the whole experiment.

JEENA AND CHING :) Present and Discuss raw data: Observations -Before mixing KCl solute with water: white and powdery; many hard chunks -When KCl is mixed with water solvent: water turns opaque; temperature decreases very quickly; powdery KCl is not visible -When stirring stops: solution returns to original clear color like water; some residue of the solute sinks to base of beaker; residue is tiny clear stones, smaller than original state of KCl; temperature of solution remains cold for at least 10 minutes Raw Data -No significant difference in electrical conductivity between the different concentrations of KCl - blahblahblah

ALLISON :) Analysis of data: -Got average of the electrical conductivity results and put it into a table -Talk about graph Trends: there is a general increase of conductivity as the amount of KCL is increased but at 20g it has a sharp drop and then from from 20g to 25g the line increases again. peaks and drops (minimum and maximum) : From 0g to 5g we are able to see a high linear increase at a faster rate from µS/cm to µS/cm which is µS/cm and from 5g to 10g the avg. the difference between the conductivity is smaller at µS/cm creating a more moderate gradient. From 10g to 15g the difference is only.134 µS/cm where it just sort of plateaus but from 15g to 20g there is a sharp drop of conductivity by.751 µS/cm and it increases again from 20g to 25g by µS/cm. As we can can see from the graph the highest electro-conductivity average is at 25g with and the lowest electro-conductivity is at 0g, which is because it contains no KCL which because KCL helps conduct electric currents within the ions. rate at which it increased and decreased: I have no clue what to write about this how often it fluctuated up and down: There is not much fluctuation until from 15g to 20g where the conductivity of the solution decreases drastically, because at 20g the KCL amount first becomes harder to dissolve because of the amount contained within the water solution at 50mL there making it harder to dissolve at from 0-15g the KCL was able to be dissolved. But at 20g to 25g it increases again which can be an error in measuring the conductivity because it should be less soluble than 20g. Therefore, it should also continue a decreasing trend but instead it increases. It would have been more logical to have a decreasing trend because it would have been harder to electric currents to pass through if it was less dissolved than the more dissolved solutions. why it fluctuated up and down: The fluctuation of the line graph has a lot to do with human errors and limitations we faced such as, temperature, amount of KCL and water used which Scott and Jeena will now discuss in more detail.

Limitations/Errors/Improvements: -Jeena: Higher temperatures of water allow ions move faster and have a higher conductivity and solubility, thus we should have used higher temperatures to dissolve the KCl solute. Our limitation was the cold water, and the KCl did not completely dissolve in the solution. But if we had used hot water, then the temperature would be another variable but in this experiment, we wanted to keep that a constant, so it might not have applied for this experiment -Scott: This can be seen as some of the solutions had some residue of the KCl remaining at the bottom of the beaker. Therefore we could have used more water so that there would be more water to dissolve the salt. It would not make sense to have the same amount of water but use smaller amounts of KCl because from the results we have, the intervals of 10g KCl does not even have much difference, so if our intervals were by 1’s, there would probably be no difference at all in electrical conductivity. -Scott: human error: although we used the same person to stir the solution each trial, but the vigorousness of that person’s stirring and the amount of time spent stirring could have varied each time and this could affect the results -Jeena: KCl's solubility at 20 degrees is 34.4g/100ml of water. This is equivalent to 17.2g of KCl/ 50ml of water, which was the amount of water we used for our experiment. Therefore, after the 15g tests, the 20g and 25g tests were oversatured. They had too much solute for the 50 ml of water solvent. Therefore, we should have used more water from the start for the rest of the solutions.

CHING :) Applications

ALLISON :) Conclusion: In conclusion, there wasn’t a significant difference between the different concentration of the Potassium Chloride Concentration, the average conductivity for the control variable (water only) at 0g and 0 seconds was at at 5g of KCL at 0 seconds it was , 10g , 50 g , and at 25g However, our data shows that there is a direct proportion between ion concentration, that is, salinity in our experiment, and level of electrical conductivity. Therefore, even though there was a negligible difference in conductivity between different concentrations, it is clear that there is a higher conductivity in ionic solutions than just plain water.