Increasing the temperature generally

Step 1: Analyze the question The question asks how a rise in temperature generally affects solubility, for both solids and gases dissolving in liquids.

Step 2: The concepts

• Solids in liquids: Dissolving most solids is endothermic, meaning it absorbs heat. By Le Chatelier's principle, adding heat (raising the temperature) shifts the equilibrium toward more dissolving. So solubility increases with temperature. Examples are sugar, KNO₃ and NaNO₃ in water. (There are exceptions, such as calcium hydroxide, but the question says "generally".)

• Gases in liquids: Dissolving a gas is usually exothermic, meaning it releases heat. Raising the temperature shifts the equilibrium the other way, so gas escapes from the solution. Solubility decreases with temperature. Also, gas molecules gain kinetic energy at higher temperatures and escape more easily. This is why a warm soft drink goes flat faster than a cold one, and why fish struggle in very warm water, which holds less dissolved oxygen.

Step 3: Check the options

• A: Reversed. The solid and gas effects are swapped, so it is wrong.
• B: Solids increase, gases decrease. This is correct.
• C: Wrong, because gas solubility does not increase.
• D: Wrong, because solid solubility does not decrease in general.

Step 4: Answer

Tip: Remember "Solids like it hot, gases like it cold." Solids dissolve better when heated, and gases stay dissolved better when cooled. Think of a cold bottle of Coke keeping its fizz.