Factors Affecting Solubility
One fun way to start learning about solutions is to open your refrigerator. Do you have any orange juice? Pour yourself a small glass. Do you have any soda or iced tea? Pour another small glass. Look through each liquid. You should notice that you can see clearly thorough both liquids—they’re transparent. You cannot see through the orange juice, however—it’s opaque. The differences between these liquids are due to the size of particles dissolved in them. Orange juice contains larger particles that are only temporarily suspended in water: if the orange sits for a while, the bigger particles settle to the bottom (that’s why you should always shake a container of orange juice before pouring!). Iced tea and soda, on the other hand, are solutions. The particles within the liquid are small enough remain suspended in the liquid, which allows light to travel through.
A solution is a homogeneous (evenly distributed) mixture of two or more substances. The substance that is present in the largest amount is called the solvent, while the substance that is present in the smaller amount is called the solute. Water is a familiar solvent, as many solutes can be dissolved in it. Check out what happens when sugar is dissolved in water. The three-atom particles are the water molecules, and the bigger white crystals are the sugar molecules. Note how each of the sugar molecules becomes surrounded by water molecules.
Problem: learn about solutions!
- Distilled water (this type of water has absolutely no minerals dissolved in it)
- White granulated sugar
- Three straws
- Clear glass
Procedure A: How Sweet It Is!
- Add two teaspoons of sugar to one cup of the distilled water.
- You are now going to see if the concentration of sugar varies in different parts of a sugar solution. Luckily, you have your own sugar detector: your tongue! You are going to draw samples of the sugar solution from the top, middle, and bottom of the cup of the sugar solution. Which location do you think will taste the sweetest? Why?
- Dip the straw into the bottom of the cup. When some of the sugar water has entered the straw, put your finger over the top of straw and lift carefully out of cup. Taste the liquid at the bottom of the straw.
- Using a fresh straw each time, repeat step 4, sampling at the middle and top of the sugar solution, respectively.
- If you are unsure of your results, try again, or have a friend repeat the experiment with you.
Procedure B: How Sweet Can it Get?
- Measure one cup of room temperature distilled water into a clear glass.
- Add 1 teaspoon of sugar. Stir.
- Continue adding sugar to the water, 1 teaspoon at a time, stirring after each addition. Make to keep track of how many teaspoons of sugar you add.
- Keep adding sugar to the solution, until the solution reaches a point where sugar no longer dissolves and instead sinks to the bottom of the glass.
- At this point, you will have made a saturated solution. A saturated solution is a solution that holds the maximum amount of that particular solute (in this case sugar) for that particular solvent (in this case water) at that particular temperature (room temperature).