Solubility is the amount of a substance that can dissolve in a certain amount of solvent, usually water, at a given temperature. In this project, students test how much sugar or salt dissolves in water at 10°C, 30°C, 50°C, and 70°C. The experiment matters because solubility explains everyday processes like making sweet tea, cooking, ocean salinity, and crystal formation.
By measuring carefully, students can turn a simple classroom activity into real scientific data.
Key Facts
- Solubility = grams of solute dissolved per 100 g of water.
- Independent variable: temperature, such as 10°C, 30°C, 50°C, and 70°C.
- Dependent variable: maximum mass of sugar or salt that dissolves.
- Controlled variables should include water volume, solute type for each trial, stirring time, and container size.
- A saturated solution contains the maximum amount of dissolved solute at that temperature.
- For many solids, solubility increases as temperature increases, but the size of the change depends on the solute.
Vocabulary
- Solubility
- Solubility is the maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature.
- Solute
- A solute is the substance being dissolved, such as sugar or salt.
- Solvent
- A solvent is the substance that does the dissolving, such as water in this experiment.
- Saturated solution
- A saturated solution contains as much dissolved solute as it can hold at that temperature.
- Supersaturated solution
- A supersaturated solution contains more dissolved solute than normally stable at that temperature and can form crystals if disturbed.
Common Mistakes to Avoid
- Changing the amount of water between trials is wrong because solubility comparisons require the same solvent amount each time.
- Adding solute too quickly is wrong because undissolved crystals may collect at the bottom before the solution has time to dissolve them.
- Comparing sugar data to salt data without labeling the solute is wrong because different substances have different solubility patterns.
- Recording the total amount added instead of the amount dissolved is wrong because solubility measures only the solute that actually dissolves.
Practice Questions
- 1 At 30°C, a student dissolves 204 g of sugar in 100 g of water before extra sugar remains undissolved. What is the solubility of sugar at 30°C?
- 2 A group uses 50 g of water at 70°C and dissolves 90 g of salt before the solution becomes saturated. What is the solubility in grams of salt per 100 g of water?
- 3 A saturated sugar solution at 70°C is cooled to 10°C. Explain why crystals may form and how this relates to the solubility curve.