Question

Why do citrus growers spray their trees with water to protect them from freezing?

Short answer

Citrus growers spray their trees with water to protect them from freezing because the water absorbs heat from the environment and, even as it begins to freeze, it releases the heat of fusion keeping trees warmer than the freezing point. This process prevents the trees from freezing and suffering cold damage.

Step-by-step solution

Introduction to heat transfer

The principle of heat transfer is crucial to understand this problem. When two objects come into contact, heat flows from the hotter object to the cooler one until they both have the same temperature - this is to achieve thermal equilibrium.

The properties of water

Water has unique physical properties, one of them being a high specific heat capacity. This means that water can absorb a lot of heat before its temperature increases significantly. Hence, when citrus growers spray water on the trees, the water absorbs the heat from the environment and maintains its temperature.

The heat of fusion

When water freezes, it undergoes a phase change from liquid to solid which requires the release of energy, also called the heat of fusion. For water to freeze, it has to release this heat which gets transferred to the surrounding trees, keeping them warmer than the freezing point.

Protection against freezing

So, when citrus trees are sprayed with water in freezing temperatures, the water absorbs the ambient heat and even when it begins to freeze, it releases the heat of fusion which helps the trees to maintain their temperature above freezing, thus protecting them from damage.