Solubility Quiz 2015 Self-Testing Guide Due the day of the quiz.
ANSWERS IN BOLD
Name: ______________________________
Students should be able to . . .
Review
Draw the temperature vs. time curve for potassium K. The melting point of Potassium (K) is 63° C. and the boiling point of K is 76° C. What state of
matter will potassium be at room temperature
76 C
63 C
Solubility
Remember when we mixed different solids in water.
1. Describe the features that make a mixture a solution and give an example.
Solutions are homogenous mixtures. As long as you have a mixture with more than one ingredient that is spread evenly throughout, you have a
solution. We have focused on liquid solutions. Everyday examples are sugar in tea, Gatorade, soda, shampoo, dish soap and window cleaner.
2. For your example above, describe the ingredient in the mixture that is the solvent and the ingredient that is the solute.
The solvent in a solution is usually the liquid that does the dissolving. In sweet tea, the solvent is the water. The solute is the thing that gets the
dissolved. In sweet tea, it is the sugar.
3. Can water dissolve all substances? How do you know?
No, everything does not dissolve in water. In our lab neither sulfur nor zinc oxide dissolved in water. Thank goodness people don’t dissolve in
water either.
4. Describe the difference between dissolving and melting.
Melting requires only one substance and an increase in heat energy. Dissolving happens when a solute breaks into separate molecules and
mixes with a solvent. Two substances are required for dissolving.
5. When you make a liquid mixture, do any of the substances change chemically?
To qualify as a liquid mixture, it must contain more than one ingredient. The substance can’t be changed through a chemical reaction. A mixture
still contains the original ingredients, they don’t chemically change each other.
Remember when we did the lab that Ms. Buelt created with colored salt.
6. What visual evidence did you see in the lab that shows the concept of concentration?
In the lab, we saw visual evidence that the salt concentration increased because as the amount of salt added increased, the color became a
darker pink, the water tasted saltier, and the water level in the cup increased.
7. When a substance dissolves in something is the matter that dissolved still present in the mixture even though it can't be seen? How do you
know?
The substance is still present when it is dissolved. The molecules of the substance just separate from each other and mix in but do not change. I
know this because when I dissolve sugar in water it tastes sweet.
8. Describe real-life examples of a lower-concentration solution and higher-concentration solution. Use the boxes to show how the
atoms/molecule would look.
Lower-concentration solutions are dilute like when all the ice melts in a soda and the flavor is weak. When you don’t add the whole packet of
Kool aide powder to the pitcher of water is another example of a dilute solution. Examples of higher-concentration solutions are when you add
lots of sugar to your tea or when you put 2 packets of hot cocoa mix into your mug of hot water. The highest concentration that will dissolve is
called a saturated solution.
Lower-concentration solution
higher-concentration solution
9. Did the low salt concentration salt water taste different from the higher concentration salt water? Support your answer with evidence.
In the lab, the low concentration salt water tasted much less salty than the solution with the highest concentration.
10. Describe the concept of concentration for a solution.
Concentration is a measure of the amount of solute that has been dissolved by the solvent.
11. When a substance dissolves in something is the matter that dissolved still present in the mixture even though it can't be seen? How do you
know?
The substance is still present when it is dissolved. The molecules of the substance just separate from each other, but do not change. I know this
because when I dissolve sugar in water it takes sweet.
12. Describe how adding salt to a cup of water could affect the volume or mass of the cup and its contents.
When I add salt ot a cup of water, the volume of the mixture will increase because the substance you are dissolving (the solute) has its own
volume (takes up space). This follows the Law of Conservation of Mass that explains matter is never made or lost but can change form.
Remember when we mixed salt with water and oil to determine if everything dissolves in everything.
13. Does everything dissolve in everything?
No, everything does not dissolve in everything. In our lab neither sulfur nor zinc oxide dissolved in water. Also we saw that salt does not
dissolve in oil.
14. What word do we use to describe a substance that doesn’t dissolve in another substance?
The word insoluble describes a substance that doesn’t dissolve in another substance. An example is sulfur in water or people in water!
15. Name 2 other solvents besides water.
As we saw with the demonstrations in class, alcohol and acetone are also solvents.
Remember when we identified an unknown compound by comparing how much would dissolve?
16. In your own words, define solubility.
Solubility describes the degree a solvent is able to dissolve a solute. A substance may have a low solubility (like salt) or a high solubility (like
sugar.
17. How could solubility be used to identify a substance?
In our unknown lab we saw how sugar dissolves easily and mixes in completely, but table salt and Epsom salt did not. So if you test the
solubility of substance in water and compare it to known substances you could identify an unknown substance.