Why does water take longer times to warm than sand?

Specific heat capacity plays an important role here. It is defined as the amount of heat needed to change the temperature of a unit mass of the substance by 1 °C. It is also known as thermal Inertia which means the resistance of a substance to any change in its temperature. A relatively small amount of water absorbs a large quantity of heat for a correspondingly small temperature rise as water has a very high capacity for storing energy. Water also takes a long time to cool as it has a tendency to resist changes in temperature. For its higher heat capacity, it takes longer time to warm in presence of hot sunlight and longer time to cool on a cold night. Sands heat capacity is very low. Therefore, it warms quickly in presence of sunlight and cools quickly at night.