Solubility Graph: Strategic Thinking

This line graph shows the solubility of five substances in water. Solubility is measured in grams of substance that can dissolve in 100 grams of water (g/100 g H₂O).

The x-axis represents temperature in degrees Celsius (°C), starting at 0°C on the left and ending at 100°C on the right. The y-axis shows mass dissolved in grams per 100 g of water, ranging from 0 to 200 g.

Five substances are shown, each as a separate line: Ammonium Chloride (NH₄Cl, blue dotted), Potassium Chloride (KCl, orange dashed), Sodium Chloride (NaCl, dark teal solid), Sodium Nitrate (NaNO₃, pink dash-dot), and Potassium Alum (KAl(SO₄)₂, green long-dash).

Four of the five lines rise as temperature increases. NaCl is the exception — its line is nearly flat from 0°C to 100°C, barely changing. Potassium Alum starts very low near 0°C and rises steeply at higher temperatures. NaNO₃ starts highest at 0°C and increases steadily. NH₄Cl and KCl show moderate upward trends throughout.

Solubility is the maximum amount of a substance (called the solute) that can dissolve in a given amount of liquid (called the solvent) at a specific temperature.

In this graph, water is the solvent and the five substances are the solutes. Solubility is measured in grams of solute per 100 grams of water.

When a solvent holds as much solute as it possibly can at a given temperature, the solution is called saturated.

• NaCl (table salt) is the most familiar substance. Notice how its line is nearly flat — temperature has very little effect on how much salt dissolves.
• KAl(SO₄)₂ (potassium alum) starts very low and rises steeply — it is extremely sensitive to temperature.
• NaNO₃ (sodium nitrate) begins as the most soluble substance at 0°C and increases steadily.

Solubility is a characteristic property — it can help scientists identify unknown substances.