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State a Chemical equation in words and determine the number i of atoms in the reactants and • Products.

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WEB TUTORIAL

What is Chemistry?

7.2 Chemical Equations

When you build a model airplane, prepare a new recipe, or mix a medication, you follow a set of directions. These directions tell you what materials to use and the products you will obtain. In chemistry, a Chemical equation tells us the materials we need and the products that will form in a Chemical reaction.

Writing a Chemical Equation

Suppose you work in a bicycle shop, assembling wheels and bodies into bicy-cles. You could represent this process by a simple equation:

Eąuation: Wheels -f- Body    —> Bicycle

t-1    i_____i

Reactants    Product

When you bum charcoal in a grill, the carbon in the charcoal combines with oxygen to form carbon dioxide. We can represent this reaction by a Chemical eąuation that is much like the one for the bicycle:

Reactants    Product

• • -•

Eąuation: C(s) + O₂(g)    COo(g)

In an eąuation, the formulas of the reactants are written on the left of the arrow and the formulas of the products on the right. When there are two or morę formulas on the same side, they are separated by plus (+) signs. The delta sign (A) indicates that heat was used to start the reaction.