Why do farmers spray water on plants the night before freezing temperatures?

Question

If you can, please also explain why hydrogen bonds are responsible for this phenomenon. Thanks.

Answer 1

This reason for this spaying proceedure seems to confuse everybody! I'm going to try to explain this, be patient.

First; most plants won't freeze unless the temperature actually gets a little BELOW freezing, due to the fact that the water/juices in plants have materials dissolved in it (I think it's about 28F; might vary by plant however).

If there was a way to keep the temperature of the plant from going BELOW ~28F you can, in some cases, save the crop.

It is a known scientific fact that when a liquid is in the process of freezing, the temperature will not go below the freezing point of the liquid as long as there is still liquid present.

Thus, by spraying water on the crops, and letting it freeze, the temperature if the ice-encased plants can't go below 32F as long as liquid water continues to be applied.

I hope this didn't further confuse you.

Sorry, I forgot about the hydrogen bonding part!

The hydrogen bonding in water is responsible for water's unusual freezing and boiling points. Water (H2O) is a very small molecule, if it weren't for the hydrogen bonding it would be a gas at room temperature! Check the Mp & Bp values for analogous molecules that don't have hydrogen bonding like H2S, H2Se.

Answer 2

Ground water will be about 60 - 65 deg F, It will have to be cooled to 32 deg F, then further heat must be removed to freeze the water (heat of fusion) and the resulting ice serves as an insulator helping to keep the temp at 32 deg F. Damage occurs when the temperature drops lower than 32 deg F.

Answer 3

They are actually attempting to keep the crop from freezing, they are leaving the water on all during the freeze in hope that it saves the crop. Frozen crops are wasted crops. Think of it this way, in a house with no heat during a freeze you leave the water on just a tiny bit. The pipes won't freeze because the water is moving. If it was holding still it would freeze. It the same with the crops, the movement of the water and the fact the water is warmer keeps the crops from freezing.

Answer 4

to prevent the plants from being frost-bitten farmers will spray the fields with water to coat the plants with a icy coat of water. the ice forms a protective barrier, keeping the fruit from being damaged. the hydrogen bonds are the same as forming an ice cube.

Answer 5

The ice forms an insulating barrier.