Glossary (Chemistry Reference Sheet)
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3Glossary
acid
A substance that tastes sour, conducts
conductivity
A property that shows how
electricity, and reacts with many metals.
easily heat or electricity fl ows through
Lemon juice is an acid. It tastes sour,
matter. Metals are good conductors because
conducts electricity, and reacts with certain
both heat and electricity fl ow easily
metals, such as iron.
through metals. Plastic and glass have poor
conductivity because heat and electricity
atom
The smallest particle of an element
don’t fl ow easily through them.
that has the properties of the element.
An oxygen atom is the smallest particle of
constant
A factor that doesn’t change in an
oxygen that has oxygen’s properties. If you
experiment. Suppose you do an experiment
divide this atom, you have smaller particles,
to fi nd out the effect of water on the
but they don’t have oxygen’s properties.
growth of plants. The only factor you would
change in the experiment would be the
atomic number
The number of protons
amount of water the plants receive. All other
contained in an atom of an element. An
factors, such as the amount of sunlight the
atom of iron contains 26 protons, so the
plants receive, the original size of the plants,
atomic number of iron is 26. Atomic number
and the type of soil the plants are grown in,
is used in identifying atoms.
must stay the same, or constant.
base
A substance that tastes bitter and feels
dependent variable
The variable that changes
slippery. Soap is a base. It tastes bitter and
as a result of changing the independent
feels slippery.
variable in an experiment. In the plant
experiment (see defi nition for constant), the
boiling point
The temperature at which a
dependent variable is the height of the plant
liquid becomes a gas. Boiling point is a
at the end of the experiment. This factor
property that is different for each substance.
changes according to how the independent
The boiling point of oxygen is low because
variable (the amount of water) changes.
oxygen is a gas at room temperature.
element
A pure substance made of only one
chemical reaction
The reaction of one or
type of atom. Copper, helium, calcium, and
more substances to produce a new substance
neon are all types of elements. Each element
with different properties. The signs that
is made up of one kind of atom. A copper
a chemical reaction has occurred include
atom is different from a gold atom.
temperature change, formation of a gas
or a solid, and change in odor or color. For
group
A column on the periodic table. The
example, when an egg fries, you know a
elements in a group on the periodic table
chemical reaction occurs because the color
have similar properties. For example,
and odor of the egg change.
fl uorine and chlorine are in the same
group. Both elements tend to react with
compound
A pure substance that contains
the same elements and are gases at room
atoms of different elements. Water is an
temperature.
example of a compound. A molecule of
water contains two hydrogen atoms and one
oxygen atom.
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GLOSSARY
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