Glossary (Chemistry Reference Sheet) Page 2
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3Glossary (continued)
independent variable
The factor in an
period
A row on the periodic table. Elements
experiment that is changed. In the plant
in a period on the periodic table change in
experiment (see defi nition for constant), the
properties as you go across the row from
independent variable is the amount of water
left to right. But when you reach the end of
the plants receive. This factor is the only one
a row and start the next row, the properties
that changed during the experiment.
of the elements start over in a pattern like
the row above it.
indicator
A substance that changes color with
a change in pH. Phenol red is an example
periodic table of the elements
A chart that
of an indicator. Phenol red is yellow in an
shows all the elements arranged by atomic
acid, red in a base, and orange in a neutral
number and by properties. The periodic
solution.
table was developed by the Russian chemist
Dmitri Mendeleev. The chart shows all the
melting point
The temperature at which a
known elements on Earth. The elements are
solid becomes a liquid. An icy road becomes
arranged according to their atomic numbers
wet when the temperature of the road rises
and their properties.
to the melting point of water. Melting point
is the same temperature as the freezing
pH
A measure of the amount of acid in a
point, where a liquid becomes a solid.
solution. A low pH means a solution is
acidic. Stomach acid has a pH of about 2. A
mixture
A combination of two or more
high pH means a solution is basic. Ammonia
substances that can be separated by physical
solution used for cleaning is a base and has
means. Bird seed is a mixture. You can
a pH of about 11.
separate the mixture into the different types
of seeds it contains. A saltwater solution is a
polymer
A large molecule made from chemical
mixture, too. The salt can be separated from
reactions between many small molecules.
the water by evaporating the water. Both
Poly means “many.” When many monomers
these methods of separation are physical
react with each other, they form a polymer.
methods because the identity of the items
A polymer can contain just a few monomer
separated does not change.
units, or it can contain tens of thousands of
them. Carbohydrates such as cellulose and
molecule
The smallest particle of a compound.
starch are polymers of certain sugars, which
The chemical formula of the compound
are monomers.
carbon dioxide (CO
) shows that a molecule
2
of carbon dioxide contains one atom of
product
A substance formed during a chemical
carbon (C) and two atoms of oxygen (O).
reaction. When a piece of paper burns, ash,
carbon dioxide, and water are products.
monomer
A small molecule that joins other
Rust is the product of the chemical reaction
small molecules to make a polymer. Proteins
between iron and oxygen. When plants
are made up of small molecules called
make food, sugar and oxygen are the
amino acids. Amino acids are the mono-
products.
mers that make up proteins. Sometimes
you can tell the name of the monomer
property
A characteristic of matter that can be
from the name of the polymer formed. For
used to identify it. If you described water,
example, polyethylene (used in plastic bags
you might say that it is a colorless, odorless
and plastic wrap) is a polymer formed from
liquid. You might mention its melting point
ethylene monomers.
and boiling point. All these characteristics
are properties of water.
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