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Energy Requirements for Freezing Water
- To freeze one gram of ice from 32 to 0 degrees Fahrenheit takes about 80 calories of energy.
- Freezing is an exothermic process releasing energy, while melting absorbs energy.
- To melt 15 grams of ice to water at 0 degrees Celsius requires 4,520.7 joules of energy.
Water Properties during Freezing
- Water expands when freezing, allowing ice to float.
- The molecules of the water are closer together at 4 degrees Celsius, increasing the liquid’s density.
Factors Affecting Freezing Duration
- Colder water freezes faster, with cold water taking about four hours to freeze, while hot water takes longer.
- Metal containers accelerate freezing compared to plastic or rubber.
Energy Requirements for Phase Changes
- To crystallize 1 kg or 1 liter of water, it takes 333 KJ of energy.
- The latent heat of fusion for freezing water is 80 calories per gram or 334 joules per gram.
- It takes 417 kilojoules in total to freeze 1 liter of water.
Differences in Energy Processes
- Melting and vaporization are endothermic processes, requiring energy.
- Freezing and condensation are exothermic processes, releasing energy.