Online labs include: Mixture Separation Living in a Thirsty World Matter and Change Why it Matters

A change in which one or more substances are converted into different 
substances is called a 
chemical change
or 
chemical reaction.
 The substances 
that react in a chemical change are called the 
reactants.
 The substances that 
are formed by the chemical change are called the 
products.
In the case of 
burning charcoal, carbon and oxygen are the reactants in a combustion, 
or burning, reaction. Carbon dioxide, a gas, and ashes are the products, 
which are clearly different from the reactants.
Figure 2.4
9
Matter and Change

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©Charles 
D.
Winters
Chemical reactions are normally written with arrows and plus signs. 
These stand for the words 
yields
and 
plus
,
respectively. For example, to 
describe the decomposition of the mercury compound shown in 
Figure 2.5,
we’d write it as follows:
mercury (II) oxide 
→
mercury 
+
oxygen
In other words, mercury (II) oxide 
yields
mercury 
plus
oxygen.
Although chemical reactions form products whose properties can 
differ greatly from those of the reactants, they do not affect the total 
amount of matter present before and after a reaction. The law of conser-
vation of mass is always followed in chemical reactions.