Chemical Reactions and Molecules

This lesson is about molecules and chemical reactions.

First:
Here are some common molecules (scroll down, choose some and you can rotate the models on the screen)

Read, then go on to next section

Molecules are compounds in which the elements are in definite, fixed ratios... Those atoms are held together usually by one of the three types of chemical bonds discussed above. For example: water, glucose, ATP.

Mixtures are compounds with variable formulas/ratios of their components. For example: soil. Molecular formulas are an expression in the simplest whole-number terms of the composition of a substance. For example, the sugar glucose has 6 Carbons, 12 hydrogens, and 6 oxygens per repeating structural unit. The formula is written C6H12O6.

Chemical reactions occur in nature, and some also can be performed in a laboratory setting. ... Chemical equations are linear representations of how these reactions occur. Combination reactions occur when two separate reactants are bonded together, e.g. A + B -----> AB. Disassociation reactions occur when a compound is broken into two products, e.g. AB -----> A + B.

Biological systems, while unique to each species, are based on the chemical bonding properties of carbon. Major organic chemicals (those associated with or formed by the actions of living things) usually include some ratios of the following elements: C, H, N, O, P, S.