## <center>The heat is a form of energy.</center>
All bodies are formed by matter. That matter is made up of molecules and atoms. Molecules and atoms are in constant motion.
That movement or agitation of the molecules produces *thermal energy or heat*. Heat is a source of energy.
<center>http://nextews.com/images/3f/4f/3f4f6ecc7ea50ed7.jpg
[Source](http://nextews.com/images/3f/4f/3f4f6ecc7ea50ed7.jpg)</center>
### Routes of energy
The energy can pass from one form to another:
- If you touch the cover of an automobile engine, you will notice that it is hot, that is, the engine has generated heat. The electrical energy passed to mechanical energy and is to heat energy or heat.
<center>http://comeresa.pd.ak.o.brightcove.com/images/800000603001/800000603001_1437845393001_ari-origin05-arc-132-1328616300695.jpg?pubId=800000603001&videoId=1427668795001
[Source](http://comeresa.pd.ak.o.brightcove.com/images/800000603001/800000603001_1437845393001_ari-origin05-arc-132-1328616300695.jpg?pubId=800000603001&videoId=1427668795001)</center>
- The chemical energy contained in the wood is transformed into light (light energy) and heat (heat energy) when it burns in a bonfire.
<center>https://www.campingchile.cl/wp-content/uploads/2010/11/fogata.jpg
[Source](https://www.campingchile.cl/wp-content/uploads/2010/11/fogata.jpg)</center>
- The electrical energy that passes through the filament of an electric bulb transforms into light and heat.
<center>http://footage.framepool.com/shotimg/qf/544535987-filament-lights-on-on-electricity-light-bulb.jpg
[Source](http://footage.framepool.com/shotimg/qf/544535987-filament-lights-on-on-electricity-light-bulb.jpg)</center>
**The energy passes from one form to another until it ends in heat energy or heat.**
> The sun is the most important source of energy for our planet and the entire Solar System. The Sun is a great chemical reaction that produces light and heat.
<center>http://1.bp.blogspot.com/-Nx5jMcxemyw/VHP1pdsClfI/AAAAAAAAAGE/yxGYwnD4so4/s1600/sol.jpg
[Source](http://1.bp.blogspot.com/-Nx5jMcxemyw/VHP1pdsClfI/AAAAAAAAAGE/yxGYwnD4so4/s1600/sol.jpg)</center>
### Temperature
Just as heat is produced by the movement of molecules, temperature is a quantity that expresses the speed of molecules.
The temperature of a body increases when the molecules move with greater speed and decreases when they move slowly.
To measure the temperature, thermometers are used. Thermometers measure the speed of movement of molecules, that is, the temperature of a body.
<center>http://www.eurosalus.com/var/eurosalus/storage/images/infiammazione-da-cibo/quella-febbre-che-torna-spesso-e-di-cui-non-si-conosce-la-causa/135078-3-ita-IT/Quella-febbre-che-torna-spesso-e-di-cui-non-si-conosce-la-causa.jpg
[Source](http://www.eurosalus.com/var/eurosalus/storage/images/infiammazione-da-cibo/quella-febbre-che-torna-spesso-e-di-cui-non-si-conosce-la-causa/135078-3-ita-IT/Quella-febbre-che-torna-spesso-e-di-cui-non-si-conosce-la-causa.jpg)</center>
### Thermometric scales
The **thermometric scales** are established from values that are chosen for two fixed points, which correspond to **the freezing temperature** (melting) and the **boiling temperature** of the water.
**The lowest possible temperature** is called **absolute zero** or zero degree Kelvin (0 ° K), and can not be obtained with the methods currently.
<center>http://www.corporativo.net.co/bibliotecainsa/biblioteca/clases/10contenido/jpg/fis_10_0455.jpg
[Source](http://www.corporativo.net.co/bibliotecainsa/biblioteca/clases/10contenido/jpg/fis_10_0455.jpg)</center>
### Balancing the heat
When your hands are cold and you take the hands of another person who has them warm, you receive that heat and yours get warm. For this reason we say that **the heat passes from a hot body to the cold** (never the reverse). This passage lasts until the two bodies **balance the temperature.**
The transfer of heat between the bodies is called thermal equilibrium.**
<center>https://d3bwu0f92zgi29.cloudfront.net/wp-content/uploads/2013/06/Holding-hands-1024x742.jpg
[Source](https://d3bwu0f92zgi29.cloudfront.net/wp-content/uploads/2013/06/Holding-hands-1024x742.jpg)</center>
### Heat transfer
<center></center>
### Effects of heat
#### Dilation
Dilation is called the phenomenon by which a body increases its volume, length or surface when receiving heat, as its molecules move with more intensity.
- Dilation of solids
According to the form they have **the solid bodies**. There are three types of dilation. We see what they are and how we check them.
**Linear Dilatation:** Take a metal rod, measure it and heat it. Then, measure it again and you will see that there is a **increase in length**.
https://www.youtube.com/watch?v=ck8Xt2R7f5g
**Surface dilation:** repeat the previous experience, but with a sheet of iron. This will prove that your surface increases.
<center>https://tatofisicatermodinamica.files.wordpress.com/2013/04/1.png
[Source](https://tatofisicatermodinamica.files.wordpress.com/2013/04/1.png)</center>
**Cubic dilation:** if you heat a sphere or cube, you can check that it increases its volume (or perform the experience of Gravesande).
<center>http://www.iesdmjac.educa.aragon.es/departamentos/fq/temasweb/FQ2ESO/FQ2ESO%20Tema%203%20La%20energia/dilataliquido.JPG
[Source](http://www.iesdmjac.educa.aragon.es/departamentos/fq/temasweb/FQ2ESO/FQ2ESO%20Tema%203%20La%20energia/dilataliquido.JPG)</center>
- Dilation of liquids
The **dilation in the liquids** produces an **increase in its volume.** For example if we heat water in a container, we will see that, after a certain time, it begins to spill.
<center>http://78.media.tumblr.com/tumblr_mddypxQhlt1rkv6lbo1_500.gif
[Source](http://repetititive.tumblr.com/post/35571970434)</center>
- Gas dilatation
In **gases, dilation** also produces an increase in its volume, but much greater than in solids and liquids.
For example: hot air occupies a volume greater than cold air, is lighter and rises. For this reason, it is used hot for hot air balloons.
<center>https://thumbs.gfycat.com/SkeletalShinyArawana-small.gif
[Source](https://thumbs.gfycat.com/SkeletalShinyArawana-small.gif)</center>
### *Curiosidates:*
> *The Dutch physicist Willem Gravesande (1688-1742) made the following experience: he built an apparatus (Gravesande ring), formed by a bronze sphere that, at room temperature, passes tightly through a hole made in the sheet metal.
When heating the sphere, it does not pass through the hole, it increases its volume when subjected to the action of heat. When it is cooled, it returns to its normal volume and can pass through the hole. In this way we check the cubic dilation.*
<center>https://i.pinimg.com/originals/4d/e4/92/4de49246370ed3c82a3a97aa0652c634.png
[Source](https://i.pinimg.com/originals/4d/e4/92/4de49246370ed3c82a3a97aa0652c634.png)</center>
Learning and teaching science.
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[Source](http://gifgifs.com/animations/science-body/science-tools/Weird_science.gif)</center>