Visual Learning Company
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23
Solutions at work
Name
Experimenting With
Concentration
Background: Have you ever taken a sip of lemonade that tasted exceptionally sweet? Or
maybe you've had soda that was fl at, or in other words had little fi zz. These experiences are
related to the concentration of solutions. What exactly is concentration? Concentration is a
measure of the amount of solute dissolved in a solvent.
What do you think has a greater concentration - a cup of tea with two tea bags, or a cup of tea
with one tea bag? The cup of tea with two tea bags has a greater concentration. In most cases
it looks darker, and tastes stronger. This is because a great deal of solute is dissolved in the
solvent - hot water. This is just one example of concentration in solutions.
Solubility is a measure of how well a solute can dissolve in a solvent at a given temperature.
Temperature plays a key role in solubility. For example, sugar dissolves much more readily
in hot tea than in iced tea. Quite often when making foods such as candy or fudge it is
necessary to heat the mixture so that sugar can be dissolved. Several factors affect how
quickly a substance is dissolved in a liquid solvent. Perhaps you've noticed someone stirring
sugar into a drink. Stirring and shaking increase the rate of dissolving. Crushing a solute also
helps accelerate dissolving. This increases the surface area of the solution being dissolved,
providing more contact with the solvent. In this activity you will experiment with some of the
factors that affect solubility.
Materials: 4 sugar cubes, 4 beakers or clear plastic cups, stirring rod or spoon, graduated
cylinder, large beakers (500 ml.) or clear plastic containers, soda
Directions:
1. In the fi rst part of this activity, you will experiment with some of the factors that affect how
quickly a solute dissolves in a solvent. The solute is sugar and the solvent is water. Obtain the
materials listed from your teacher.
2. Label the beakers or clear plastic cups one to four.
3. Obtain four sugar cubes. Crush two of the cubes on separate pieces of scrap paper.
4. Place 100 ml. of hot tap water in container 1. Place a complete sugar cube in the container.
Stir while recording the amount of time necessary for the cube to completely dissolve. Record
the time in the data table.
5. Place 100 ml. of hot tap water in container 2. Place the crushed sugar in container 2. Stir
while recording the time it takes the sugar to completely dissolve. Record the time in the data
table.
6. Place 100 ml. of cold water in container 3. Place a complete sugar cube in the container.
Stir while recording the amount of time necessary for the cube to completely dissolve. Record
the time in the table.
7. Place 100 ml. of cold water in container 4. Place the crushed sugar in container 4. Stir while
recording the time it takes the sugar to completely dissolve. Record the time in the data table.