Standard enthalpy change of fusion of period three.

Standard enthalpy change of fusion of period two of the periodic table of elements.

The standard enthalpy change of fusion (symbol: Δ_fusH), also known as the heat of fusion, is the amount of thermal energy which must be absorbed or evolved for 1 gram of a substance to change states from a solid to a liquid or vice versa. It is also called the latent heat of fusion or the enthalpy of fusion, and the temperature at which it occurs is called the melting point. Image File history File links Enthalpy_of_Fusion_period_three. ... Image File history File links Enthalpy_of_Fusion_period_three. ... Image File history File links Molar_heat_of_fusion_period_two. ... Image File history File links Molar_heat_of_fusion_period_two. ... The periodic table of the chemical elements, also called the Mendeleev periodic table, is a tabular display of the known chemical elements. ... Enthalpy (symbolized H, also called heat content) is the sum of the internal energy of matter and the product of its volume multiplied by the pressure. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... BIC pen cap, about 1 gram. ... In jewelry, a solid gold piece is the alternative to gold-filled or gold-plated jewelry. ... A liquid will usually assume the shape of its container. ... Fig. ... The melting point of a solid is the temperature at which it changes state from solid to liquid. ...

When you withdraw thermal energy from a liquid or solid, the temperature falls. When you add heat energy the temperature rises. However, at the transition point between solid and liquid (the melting point), extra energy is required (the heat of fusion). To go from liquid to solid, the molecules of a substance must become more ordered. For them to maintain the order of a solid, extra heat must be withdrawn. In the other direction, to create the disorder from the solid crystal to liquid, extra heat must be added. To meet Wikipedias quality standards, this article or section may require cleanup. ... Fig. ... The melting point of a solid is the temperature at which it changes state from solid to liquid. ... In chemistry, a molecule is an aggregate of at least two atoms in a definite arrangement held together by special forces. ...

The heat of fusion can be observed if you measure the temperature of water as it freezes. If you plunge a closed container of room temperature water into a very cold environment (say −20 °C), you will see the temperature fall steadily until it drops just below the freezing point (0 °C). The temperature then rebounds and holds steady while the water crystalises. Once completely frozen, the temperature will fall steadily again.

The temperature stops falling at (or just below) the freezing point due to the heat of fusion. The energy of the heat of fusion must be withdrawn (the liquid must turn to solid) before the temperature can continue to fall.

The units of heat of fusion are usually expressed as:

1. joules per mole (the SI units)
2. calories per gram (old metric units now little used, except for a different, larger calorie used in nutritional contexts)
3. British thermal units per pound or Btu per pound-mole

• Note: These are not the calories found in food. The calories found in food are more properly known as kilocalories—equal to 1000 calories. 1000 calories = 1 kilocalorie = 1 food calorie. Food calories are sometimes abbreviated as kcal as if small calories were being used, while calories are abbreviated as cal. Another distinguishing method, though often confusing, uses capitalisation. A Calorie is a food calorie, or 1000 calories. So 1 Cal = 1000 cal.

The joule (symbol: J) is the SI unit of energy, which is defined as the potential to do work. ... The mole and its simple conversions into different units of measurements. ... Cover of brochure The International System of Units. ... A calorie is a unit of measurement for energy. ... The British thermal unit (BTU or Btu) is a unit of energy used in the United States. ... A calorie refers to a unit of energy. ... A calorie refers to a unit of energy. ...

Reference Values

The heat of fusion of water is Water is a tasteless, odourless substance that is essential to all known forms of life and is known as the universal solvent. ...

79.72 calories per gram

or 334.5 joules per gram

The heat of fusion of a few more common substances:

These values are from the CRC Handbook of Chemistry and Physics, 62nd edition. The CRC Press, LLC is a publishing group which specializes in producing technical books in a wide range of subjects. ...

Application

To heat one kilogram (about 1 liter) of water 20 °C from 10 °C to 30 °C requires 20 kcal.
However, to melt ice and raise the resulting water temperature 20 °C requires extra energy. To heat ice from 0 °C to water at 20 °C requires:

(1) 80 cal/g (heat of fusion of ice) = 80 kcal for 1 kg

PLUS

(2) 1 cal/(g·°C) = 20 kcal for 1 kg to go up 20 °C

= 100 kcal

See also

• Heat of vaporization
• Heat capacity
• Specific heat capacity
• Thermodynamic databases for pure substances