How do you know if the solution is cooled or heated?

How do you know if the solution is cooled or heated?

Solubility increases with increasing temperature and decreases with increasing temperature.

When the saturated solution is heated, there must be crystal precipitation?

Not necessarily. The solubility of most substances in water decreases with the decrease of temperature, but the solubility of some substances increases with the decrease of temperature, such as calcium hydroxide. For the latter kind of substances, there is no crystal precipitation when the saturated solution is cooled down. Generally, temperature has an effect on the solubility, but the effect is large and small. The second problem,...