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This drawing represents a comet bringing atmospheric molecules and possibly primitive life forms to the Earth's surface.
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Like an acid, a base is a substance capable of dissolving things. Unlike an acid in which the active agent is a substance which has a positive electric charge (H+), in a base the active agent has a negative charge (OH-). Here are a couple of scientific explanations of what a base is:

A base is any substance that upon dissolving in water increases the hydroxide ion content (OH-). An base can also be thought of as a substance which accepts a proton from another species in a reaction. (Here, "accept" is a passive term for what really happens. A base attacks and "rips" a proton from a substance which has any capability of giving it away. Thus a base accepts a proton the way a thief "accepts" your purse). Bases are classified as either strong or weak depending upon their relative ability to do this.

There are many bases. Here are a few: Ammonia (used as a cleaner), Calcium hydroxide (used in mortar for construction), Magnesium hydroxide (otherwise known as milk of magnesia; used as a laxative or antacid), Sodium hydroxide (used as an oven cleaner).

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Nitric Acid - HNO3

Nitric acid is a colorless, corrosive liquid and a toxic acid which can cause severe burns. Nitric acid consists of nitrogen, oxygen, and hydrogen atoms. Nitric acid, in its gas phase, is present in very...more

Sulfuric Acid - H2SO4

Sulfuric acid is a viscous, oily liquid and a strong acid which can cause severe burns. Sulfuric acid consists of sulfur, oxygen, and hydrogen atoms. Sulfuric acid is one of the components of acid rain....more

Methane - CH4

Methane is gas that is found in small quantities in Earth's atmosphere. Methane is the simplest hydrocarbon, consisting of one carbon atom and four hydrogen atoms. Methane is a powerful greenhouse gas....more

Ammonia - NH3

Ammonia is a chemical compound that is a colorless, flammable gas at normal temperatures and pressures. Ammonia is toxic, corrosive to some materials, and has a pungent odor. An ammonia molecule (NH3)...more


Nitrogen is a chemical element with an atomic number of 7 (it has seven protons in its nucleus). Molecular nitrogen (N2) is a very common chemical compound in which two nitrogen atoms are tightly bound...more


Oxygen is a chemical element with an atomic number of 8 (it has eight protons in its nucleus). Oxygen forms a chemical compound (O2) of two atoms which is a colorless gas at normal temperatures and pressures....more

Hydrogen Peroxide - H2O2

Hydrogen peroxide (H2O2) is a chemical compound consisting of two oxygen atoms and two hydrogen atoms. It is a clear liquid at normal temperatures and pressures. Hydrogen peroxide is a very reactive chemical....more

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