Give an example of a process in which no heat is added to a system, but its temperature increases. Then give an example of the opposite: a process in which heat is added to a system but its temperature does not change.
No heat added, but temperature increases
Let us assume that we have a gas chamber filled with a certain amount of gas. If some amount of gas is allowed to flow out of the system, its pressure will decrease. This decrease in pressure will be accompanied by a decrease in temperature. Similarly if some amount of gas is now introduced to the chamber, the pressure inside it will increase. This will be followed by an increase in temperature of the gas. Pressure and temperature are directly related to each other. Thus, without any heat added, the temperature of the chamber increases.
Heat is added to a system but its temperature does not change
Phase change of a material from one state to another is an example where heat is added to a system, but there is no increase in temperature. Heating a wax candle is such an example, where there is a phase change of the candle from solid to liquid, but there is no increase in temperature. There is a continuous supply of heat to the candle, but once the wax reaches its melting point, there is no further increase in temperature. It undergoes a change in its state at a constant temperature.