What substances lower the freezing point of water?

Foreign particles generally lower the freezing point of water. Other materials that lower the freezing point of water are alcohols, sugars and salts. At zero degree Celsius, which is the freezing point of water, these materials make the water to be in liquid state instead of been a ice.

Adding any impurity to water lowers its freezing point. Pure water freezes at 0 degrees Celsius. However, water that contains anything other than water molecules would freeze at a lower temperature. This is the reason why salt is added to roads in the winter. The addition of the salt, an impurity, allows the water to freeze at a much lower temperature than 0 degrees. Therefore, the temperature could be 0 degrees and the water on the road would still be a liquid preventing slippage.