# Solubility Inquiry (Example Work Sample Write-Up)

Solubility Inquiry (Example Work Sample Write-up)

Title:How Temperature Affects the Solubility of Table Salt

Background:

In this inquiry, the affect of temperature on the solubility of table salt (NaCl) will be investigated. Solubility is a physical property that measures the amount of a solute that can be dissolved in a solvent. In the case of this experiment, the solute is the salt and the solvent the water. Solubility is measured in grams/L or grams/mL. It can be found by measuring how much mass of a solute dissolves in a specific volume of solvent until saturation is reached. Saturation occurs when no more solute can be dissolved in the solvent (water in this case). This can be seen when the solute or salt crystals no longer dissolve but remain in solid crystal form.It is expected that temperature will have an impact on the solubility of salt since it is known that increases in temperature cause matter to expand and the molecules or atoms to spread further apart and speed up. Therefore, the hypothesis of this investigation is that increased temperature will increase the solubility of salt. It is expected that the increased spacing and increased speed or motion of the atoms or molecules will allow more solute to dissolve in the solvent.

Procedure:

1. Put 10 mL of room temperature water into a test tube using a graduated cylinder to measure the volume. (Record the temperature of the water)
2. Mass the container of solute (NaCl) and record the data.
3. Take out one scoop of solute and drop into the test tube and shake 50 times.
4. Repeat step 3 until a small amount of solute is visible at the bottom of the test tube.
5. Re-mass the container of remaining solute and record the data.
6. Calculate the difference in mass (this equals the mass of the solute used) and record.
7. Calculate the solubility by dividing the mass of solute used by 10 ml of water (solvent). Record this down.
8. Repeat steps 1-6 two more times to get three trials with room temperature water.
9. Repeat all steps 1-8 for hot water. (Record down the hot water temperature)

Data:

Solvent
Temperature 0C / Mass NaCl
Before (g) / Mass NaCl
After (g) / Change
in Mass (g) / Volume
(mL) / Solubility
(g/mL)
19 / 30 / 23.5 / 6.5 / 10 mL / 0.650
94 / 23.5 / 15.3 / 8.2 / 10 mL / 0.820

Graph of solubility vs. temperature data:

Analysis/Conclusion:

This inquiry was done for the purpose of investigating how temperature affected the solubility of table salt (NaCl). The resulting data from the investigation shows that the solubility is impacted by increasing temperature. The results show that the higher the temperature of the water or solvent, the higher the solubility. The solubility of salt in water at room temperature (19 C) was an average of 0.65 g/mL. When the water was heated to 94 C the solubility increased to an average of 0.82 g/mL. These results confirm the hypothesis that higher temperature will allow more solute to be dissolved.This could be explained by the increased motion and energy of the molecules in higher temperature water. This would do two things; one is overcoming the intermolecular attraction between water molecules and allowing more NaCl (solute) molecules to fit in between the water molecules. The other is that the higher energy particles collide with the solid solute and break the solute bonds and cause more solute particles to break free and mix among the solvent molecules. Both would result in an increase in the solubility.

The experiment was overall a success. Potential errors in the experiment may have occurred when trying to determine the saturation point of the salt. Additional salt may have been added after saturation was reached due to relying on the human eye and judgment of when solute could be seen at the bottom of the test tubes. This extra salt would have increased the change in mass of solute used and increased the value of solubility. To avoid this in future experiments more time should be allowed for the salt to dissolve before adding more scoops to ensure the correct saturation point is found.