Lesson 2.3 What Affects Solubility?

The instructions on a package of Jello indicate that you first dissolve the powder in some hot water. Then, you add cold water to the solution. Why not just dissolve it in the full amount of water to start with?

This next investigation will help explain the instructions for making Jello. Three chemicals were used and the quantity of each chemical that could dissolve in 1 L of water was measured for a range of temperatures.

Read the investigation How Does Temperature Affect Solubility? on page 47 of your textbook.

Question 1. Draw the graph of the data as described in "What To Do" on page 47.

Question 2. Answer questions 1 to 4 in Analyse.

Question 3. Answer question 5 in Conclude and Apply.

Then, return here to continue this lesson.

 

 

How does the investigation you just performed help explain the instructions for making Jello? The solubility of the Jello powder is greater in hot water than in cold water. To dissolve the powder in cold water is very difficult, but in hot water, it dissolves quite easily. Therefore, you dissolve the powder in hot water first, then add cold water to get the required volume of water. You put the solution in the fridge so that the gelatin sets, and then you have Jello ready to eat.


Click on the page forward to continue Lesson 2.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. Draw the graph of the data as described in What To Do on page 47.

Your graph should be similar to this one.

Question 2. Answer questions 1 to 4 in Analyze.

1. The graphed lines of sodium chloride and ammonium chloride are straight. The graphed line of potassium chlorate is curved.

2. As the temperature increases, the graphed lines rise to the right.

3. A vertical line is drawn at 95°C and the solubility for each substance is read from the graph. The solubility for each is approximately as follows:
sodium chloride: 400 g/L
potassium chlorate: 575 g/L
ammonium chloride: 720 g/L


4. At 20°C, sodium chloride has the highest solubility. At 60°C and 95°C, ammonium chloride has the highest solubility.

Question 3. Answer question 5 in Conclude and Apply.

5. The solubility of a solute increases as the temperature increases. Note that this is true for most soluble substances. However, if the substance is insoluble, the temperature increase will not increase solubility.

Click to return to where you left off in this lesson.