Name: _______________________________________ Per: _____ Date: _______________
Measuring Solubility
A solution forms when one substance is dissolved by another. The substance that dissolves is
called the solute. The substance that dissolves it is called the solvent.
When you make Kool-Aid, what is the solute? What is the solvent?
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
Solubility is the amount of solute that can dissolve in a given amount of solvent at a given
temperature. Water is a common solvent, because many substances can dissolve in water.
Some solutes have greater solubility than others. For example, sugar is much more soluble in
water than salt is. But even sugar has an upper limit on how much can dissolve in water.
The solubility of a substance can be given a number value. For example, the solubility of baking
soda in water at room temperature is 10. This means that if you have exactly 100mL of water,
you cannot dissolve more than 10g of baking soda in the water. Table salt has a solubility of 37.
Other substances, like flour, are insoluble. This means they cannot dissolve in water at all.
Put the following materials in order from LOWEST solubility to HIGHEST solubility: Salt, flour,
baking soda, sugar.
_________________________________________________________________________________________________________
Gases also have solubility values. Soda is made by dissolving carbon dioxide gas in water.
Carbon dioxide has a solubility of 0.145 in water at room temperature.
How many grams of carbon dioxide can dissolve in 200mL of water? ________________
In this activity, we will be using solubility to identify unknown substances.
Our Story: Robsen wants to make a cake at his aunt’s house for his cousin’s birthday. His aunt
has all the ingredients he needs, but she keeps her ingredients in clear containers and the labels
accidentally fell off. Robsen needs to find out which substance is sugar, which one is salt, which
one is flour, and which one is baking soda. He is allergic to sugar and has gluten intolerance, so
he can’t taste them. Instead, he decides to use solubility as a way to identify the substances.
Materials
Beaker
Teaspoon
4 unknown substances
Digital Balance
Procedure
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
_________________________________________________________________________________________________________
Data table
Substance
Starting mass of
beaker + water
Ending mass
of beaker +
water +
substance
Total mass of
substance added
(starting – ending)
1
2
3
4
Based on your data, what are each of these substances?
Substance Number
1
2
3
4
What is it?
Did the substance
dissolve?
Name: _______________________________________ Per: _____ Date: _______________
Measuring Solubility Part 2: Calculating Concentration
Concentration is a measure of how much solute is in a given volume of solvent. A higher concentration
means there is MORE solute that is dissolved. A lower concentration means there is LESS solute that is
dissolved in the liquid.
Zachary has a cup of hot chocolate that he thinks is not concentrated enough. What should he do to
make it more concentrated? Check all that apply.
□
□
□
He should pour half of the hot chocolate into another cup.
He should add more water to the hot chocolate.
He should add more hot chocolate mix to the hot chocolate.
In the example above, the solute is ________________________. The solvent is ___________________.
In chemistry, the solute/solvent (circle one) is usually expressed as mass. The solute/solvent (circle one)
is usually expressed as volume.
When you measured the solubility of different substances, you were increasing their concentrations
every time you added another spoonful of the substance to water. The concentration of a solution is
shown as the mass of solute dissolved in every 100mL of solvent (water).
If you have a beaker of 35 grams of sodium chloride (salt) dissolved in 250mL of water:
1. What is the concentration of this solution? (include units and show your work)
2.
If 50 ml of the solution was poured into another container, what would the concentration be?
3.
What would be the concentration of the solution if we added another 150mL of water to the
original 250mL of solution?
4.
What would be the concentration of the solution if we added 60 grams of salt to 250 mL of
water?
5. You have a beaker of plain water and a beaker of a very concentrated solution of sugar and
water. You add sugar-water solution from beaker 2 to beaker 1 three separate times. A graph of
the contents of beaker 1 is shown below for the three times that sugar-water solution is added
(A, B, and C).
Using the data from the graph, answer each question and explain how you determined your answer.
a. What volume of sugar-water solution was added in the last pour? ____________________________
b. What was the concentration of the sugar-water solution in beaker 1 at Point C? ________________
Explain how you determined your answer.
c. What was the concentration of the sugar-water solution originally in beaker 2? _________________
Explain how you determined your answer.
c. How much water was in beaker 1 at the beginning of the experiment? __________________________
Explain how you determined your answer.
d. Two students are discussing the idea of concentration with each other. Help the students resolve
their disagreement.
Student 1: “I have 25 ml of solution in this test tube. Student 2: “That doesn’t make sense. First you say
It has a concentration of 3.1g/100ml.” that you have 25 ml of solution, then you say you have 100ml.”
Do you agree with Student 2? Why or why not?
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________