Easy ! EVERY element and every compound melts, then boils and becomes a gas, if you heat it to a high enough temperature. That includes iron, gold, water, salt, glass, almost any substance.
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At the Earth's surface, warm air expands and rises, creating
what is known as an area of low pressure.
Cold air is dense and sinks to the surface to create what is
known as an area of high pressure.</span>
So that we do not contaminate it with microorganisms or garbage or other human stuff.
The characteristic of epithelial cells that makes them ideal for providing this type of protection is that the cells are packed tightly together.
Skin, the body's largest organ,is our first and best defense against external aggressors. The many layers work hard to protect us, however when its condition is compromised, its ability to work as an effective barrier is impaired.
