Gases:
* Inverse Relationship: The solubility of most gases in water decreases as the temperature increases.
* Explanation:
* Kinetic Energy: Higher temperatures give gas molecules more kinetic energy. They move faster and are more likely to escape from the liquid phase, reducing their solubility.
* Intermolecular Forces: Gases dissolve in water primarily due to weak interactions (van der Waals forces) between the gas molecules and water molecules. Increasing temperature weakens these forces, making the gas less likely to stay dissolved.
Examples:
* Carbon dioxide (CO2): You'll notice that a can of soda goes flat more quickly at room temperature than in the refrigerator. This is because the CO2 gas becomes less soluble as it warms up.
* Oxygen (O2): Cold water holds more dissolved oxygen, which is important for aquatic life.
Solids:
* Direct Relationship: The solubility of most solids in water increases as the temperature increases.
* Explanation:
* Energy Input: Increasing temperature provides more energy to break the intermolecular forces holding the solid together, allowing it to dissolve more readily.
* Entropy: Dissolving a solid often leads to an increase in entropy (disorder). Higher temperatures favor this increase in entropy.
Exceptions:
* Some solids show a decrease in solubility as temperature increases: This is often due to complex chemical interactions or the formation of new, less soluble compounds at higher temperatures.
Examples:
* Salt (NaCl): You can dissolve more salt in hot water than in cold water.
* Sugar (Sucrose): Sugar dissolves much more readily in hot tea or coffee.
Key takeaway: In general, gases become *less* soluble in water as temperature increases, while solids become *more* soluble. However, there are exceptions to these general trends.
