reactants and products

from reactants to products

All chemical reactionsincluding a candle burninginvolve reactants and products. Reactants are substances that start a chemical reaction. Products are substances that are produced in the reaction. When a candle burns, the reactants are fuel (the candlewick and wax) and oxygen (in the air). The products are carbon dioxide gas and water vapor.

relating reactants and products

The relationship between reactants and products in a chemical reaction can be represented by a chemical equation that has this general form: Reactants Products The arrow () shows the direction in which the reaction occurs. In many reactions, the reaction also occurs in the opposite direction. This is represented with another arrow pointing in the opposite direction (). Q: Write a general chemical equation for the reaction that occurs when a fuel such as candle wax burns. A: The burning of fuel is a combustion reaction. The general equation for this type of reaction is: Fuel + O2 CO2 + H2 O Q: How do the reactants in a chemical reaction turn into the products? A: Bonds break in the reactants, and new bonds form in the products.

breaking and making chemical bonds

The reactants and products in a chemical reaction contain the same atoms, but they are rearranged during the reaction. As a result, the atoms end up in different combinations in the products. This makes the products new substances that are chemically different from the reactants. Consider the example of water forming from hydrogen and oxygen. Both hydrogen and oxygen gases exist as diatomic (two-atom) molecules. These molecules are the reactants in the reaction. The Figure 1.1 shows that bonds must break to separate the atoms in the hydrogen and oxygen molecules. Then new bonds must form between hydrogen and oxygen atoms to form water molecules. The water molecules are the products of the reaction. Q: Watch the animation of a similar chemical reaction at the following URL. Can you identify the reactants and the product in the reaction? Click image to the left or use the URL below. URL: A: The reactants are hydrogen (H2 ) and fluorine (F2 ), and the product is hydrogen fluoride (HF).


instructional diagrams

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chemical changes occur because of chemical reactions.

-->  a. true

b. false

an example of a chemical change is a candle burning.

-->  a. true

b. false

any substance that starts a chemical reaction is called a

a) reactor.

b) regent.

-->  c) reactant.

d) none of the above

any substance that results from a chemical reaction is called a

a) producer.

-->  b) product.

c) productor.

d) none of the above

products of a combustion reaction include

a) fuel.

b) oxygen.

-->  c) water.

d) two of the above

diagram questions

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