Pure water in nature will freeze at 0℃ under normal atmospheric pressure. If water contains impurities, the freezing point of water will drop with the increase of pressure. The melting point of ice is the freezing point of water, and with the increase of atmospheric pressure, the melting point of ice also increases. Naturally formed ice is called natural ice, and ice usually made by artificial refrigeration is called artificial ice, machine-made ice or industrial ice, among which there are many kinds of artificial ice, and commonly used ice includes industrial ice, edible ice and dry ice.
Ice is a transparent hexagonal crystal structure. Pure water will freeze at 0℃ under normal atmospheric pressure. If water contains impurities, the freezing point of water will drop with the increase of pressure, and the melting point of ice is the freezing point of water. With the increase of atmospheric pressure, the melting point of ice will also increase.