Factors Affecting Solubility
A solution is a liquid mixture with two or more components. The liquid part of the mixture is called the solvent, and the smaller dissolved part of the mixture is called the solute. Solutions are assumed to be uniform mixtures, meaning that the solute is evenly spread throughout the whole mixture. When the solvent of a liquid solution is water, we refer to the solution as an aqueous solution.
A solute can be a solid, liquid or gas, and each has a particular solubility in a given solvent. Solubility refers to how much of a solute that can be dissolved in a given amount of solvent. When the maximum amount of a solute is dissolve the solution is considered saturated. When there is more solute than what can be dissolved by the solvent, the solution is considered supersaturated. In supersaturated solutions, the part of the solute that was incapable of dissolving shows up in the form of solid particles, layers in the liquid, or gas bubbles.
Solubility can be very useful in helping to purify products. Cooling down a solution until a solid solute comes out is called “crashing out.” When the solute assumes the form of crystals, this process is referred to as crystallization. The crystals that form are pure products, and can be very pretty!
There are several factors affecting solubility, including temperature and pressure. In the following experiments, you'll learn whether each factor has a positive or negative effect on the solubility of different compounds.
Objective: Explore the concept of solubility.
Will heating or cooling increase solubility? What about pressure?
- 4 small, sealed bottles of soda
- Labeling tape
- Jar or drinking glass
- Olive oil
- Small cooking pot
- Wooden skewer
- Table sugar
- Label each of the small, sealed soda bottles with a number. Two will be refrigerated overnight, and two will not.
- Open one of the bottles that will be refrigerated and one of the bottles that will be left out and let each sit with the cap off for a few minutes. What does this do? Record your observations.
- Place one of the sealed bottles and one of the open bottles in the refrigerator to allow them to cool overnight.
- Place the last two bottles somewhere warm, like a sunny window, and leave them there overnight.
- The next day, when the two refrigerated bottles are sufficiently cooled and the other two are room temperature or warmer, set the bottles out side by side and record any observations.
- It’s time to shake them up! Shake each bottle about 20 times. For each of the two bottles that you opened, plug the mouth with your thumb as you shake.
- Don’t let the gas escape just yet! Observe what happens to the bubbles in the container. Record your observations.
- If you want to make a mess (which can sometimes be fun), take the bottles over to the sink and open them (carefully!). Record your observations.
- Set out a jar or drinking glass.
- Pour small amounts of olive oil and water into the glass at the same time until the jar or glass is half full. Record your observations.
- Let the mixture sit for a few minutes. Does anything change?