All matter has a capacity to hold heat, measured as its specific heat or heat capacity. Heat capacity and temperature are not the same thing at all.
Heat makes changes happen, including expansion and contraction. The varying expansion coefficients of materials can be measured and used in many ways.
Heat generally increases the chemical rate of reaction, and it can also cause pyrolysis, the breakdown of compounds under the application of heat.
Heat at the junction of two metals causes a potential difference. The thermocouple formed can be used to generate electricity or to measure temperature.
Heat is a form of energy and travels mainly as infrared radiation, but also by convection and conduction. Heat may be converted to other forms of energy.
In 1849, William Thomson ( Lord Kelvin ) coined the term 'thermodynamics' to describe the science of heat flow which is basic to the scientific study of energy.
The movement of heat happens in accordance with the laws of thermodynamics, especially the second law, which means heat goes from warmer to cooler areas.
Sufficient heat will make a change of state happen: boiling, condensing, melting, solidifying (freezing), sublimation, to form gases, liquids and solids.
The rate at which bodies cool follows Newton's law of cooling. As the difference between an object and its environment gets less, the rate of cooling slows.
When matter is heated, energy is gained and the molecules move or vibrate faster. As matter cools, the molecules lose energy and move or vibrate more slowly.
Heat generally travels from hot to cold. Convection occurs in gases and liquids. Conduction occurs in solids, liquids and gases. Radiation can occur in a vacuum
Isaac Newton showed that the rate of cooling in a hot body was proportional to the difference between it and its surroundings: that hot things cool faster.
Metals are usually good conductors of heat, non-metals are usually poor conductors. Conduction is the transfer of energy from one atom or molecule to the next.
A higher temperature means more energy has been stored in a body than when it was a lower temperature. Temperature can be measured with a thermometer.
Refrigeration depends on adiabatic cooling to move heat from one place to another, pumping it out of the cold compartment. Cold is an absence of heat.
There is a lowest possible temperature, called absolute zero. Matter which is at absolute zero on the Kelvin scale is completely motionless in all dimensions.
In 1761 Joseph Black discovered that ice absorbs heat without changing temperature when melting, and outlined the effects of latent and specific heats.
Latent heat is absorbed or released during a change of state. This is why steam at 100º C contains more heat than an equal mass of water at 100º C.
In 1798, Count Rumford reported that mechanical energy could be converted to heat when cannon barrels were bored with drills, whether they were blunt or sharp.
By careful measurement, Count Rumford was able to establish that if heat had any mass, then a single calorie had to be less than 0.000013 milligrams.
William Herschel used a thermometer to detect heat falling outside the visible solar spectrum, and so became the first to observe infrared radiation.
We cannot see infrared radiation, although we can detect it as heat, and we can also detect it with some photographic films and special cameras.