Melting and Freezing.




Question: How does a substance change between from a solid to a liquid? How does a substance change from a liquid to a solid?


Melting:
Melting is when a solid turns into a liquid. When heat is added to a solid substance and the temperature is increasing the substance will begin to melt and eventually turn into a liquid. When a solid turns into a liquid it means that heat and energy have been added to the substance. The arrangement of the atoms will also change. Solids' atoms are generally in an arranged pattern and the atoms are closely packed together with no movement. When a solid turns into a liquid the atoms' organization will change. The atoms of a liquid move more freely though they move relative to each other, but they are also still close together.
The temperature where a solid turns into a liquid, or melts, is its melting point. Different substances have different melting points. Although a certain substance will usually have the same melting and freezing point. For example, the melting point for ice (solid form of water) is 32°F which is 0°C and 273 Kelvin. That means that when ice is left at these temperatures it will change into a liquid (water) as the temperature continues to rise. The melting point for water is also the same as its freezing point. Another example is the melting point of hydrogen. The melting point of hydrogen is -259.2°C which is approximately -435°F and around 13.95 Kelvin. Hydrogen's melting point is also the same as its freezing point.


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Freezing:
Freezing is when a liquid turns into a solid. When the temperature decreases the liquid will freeze and change into a solid. When a liquid substance changes into a solid some of its heat and energy have been lost, and for a liquid to turn into a solid the temperature decreases so heat and energy have also been decreased. The arrangement of the liquids' atoms will also change. The atoms of a liquid move freely but relative to each other but they stay close together. When the liquid changes into a solid the atoms will alter and stay packed together in an arranged pattern with no movement.
The temperature at which a liquid turns into a solid, or freezes, is its freezing point. Different substances have different freezing points, although the melting and freezing point for a certain substance is usually the same. For example, the freezing point for water is 32°F which is 0°C and 273 Kelvin. Which means if water is left at those temperatures it will freeze and turn into a solid (ice) as the temperature continues to decrease. The freezing point for water is also the same as its melting point. Another example is the freezing point for hydrogen. The freezing point of hydrogen is -259.2°C which is also around -435°F and about 13.95 Kelvin. The freezing point for hydrogen is also the same as its melting point.


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Resources:
"Phase Changes." States of Matter. Expert Space, 2011." Web. 4 Feb. 2011. <http://e21.grolier.com/article?id=10001962&product_id=ngo&searchTerm=physical%20changes&queryParser=Grolier_En&docKey=Li4vLi4vc2VhcmNoL2NvbnRlbnQvbmdvMS90ZXh0LzEwOS8xMDAwMTk2Mi5odG1sQG5nbzE*>.

"Converting between Fahrenheit and Celsius temperature scales."Copyright 2011 USA TODAY, Web. 9 Feb. 2011. <http://school.nettrekker.com/goExternal?np=/external.ftl&pp=/error.ftl&evlCode=101246&productName=school&HOMEPAGE=M>.

"Bent, Henry A. "Freezing Point." Grolier Multimedia Encyclopedia. Grolier Online, 2011." Web. 6 Feb. 2011. <http://e21.grolier.com/article?id=0112450-0&product_id=gme&searchTerm=freezing%20point%20for%20different%20element&queryParser=Grolier_En&docKey=Li4vLi4vc2VhcmNoL2NvbnRlbnQvZ21lMy90ZXh0LzEzNy8wMTEyNDUwLTAuaHRtbEBnbzI*>.

"Melting Point." Encyclopedia Americana. Grolier Online, 2011.." Web. 6 Feb. 2011. <http://e21.grolier.com/article?id=0266660-00&product_id=ea&searchTerm=melting%20point%20of%20different%20elements&queryParser=Grolier_En&docKey=Li4vLi4vc2VhcmNoL2NvbnRlbnQvZWE0L3RleHQvMDYwLzAyNjY2NjAtMDAuaHRtbEBnbzI*>.

Images:
Phases and Equilibrium. Web. 7 Feb. 2011. <http://school.nettrekker.com/goExternal?np=/external.ftl&pp=/error.ftl&evlCode=66850&productName=school&HOMEPAGE=M>.

Phase Changes. Web. 9 Feb. 2011. <http://e21.grolier.com/article?id=10001962&product_id=ngo&searchTerm=physical%20changes&queryParser=Grolier_En&docKey=Li4vLi4vc2VhcmNoL2NvbnRlbnQvbmdvMS90ZXh0LzEwOS8xMDAwMTk2Mi5odG1sQG5nbzE*>.