Matter is anything that has mass and takes up space.

Mass is a measure of the amount of matter in an object. It is measured in grams using a triple beam balance or an electronic scale.

Volume is the amount of space an object occupies. Liquid volume is measured in liters or milliliters. Volume of solid objects is measured in cm3 (cubic centimeters).

Density is the amount of matter (mass) in a certain space (volume). You can calculate density by dividing the mass of an object by its volume. Density is measured in grams per cubic centimeter (g/cm3).

The mass of an object comes from the atoms that it is made of. All atoms are made of protons, neutrons, and electrons. Atoms get most of their mass from protons and neutrons. The number of protons in the nucleus of an atom determines the type of element it is.

An element is a substance which cannot be broken down or changed into another substance using chemical means. Elements may be thought of as the basic chemical building blocks of matter. There are 118 known elements. Each element is identified according to the number of protons it has in the atom’s nucleus.

A molecule is formed when two or more atoms join together chemically.

A compound is formed when two or more atoms of different elements are chemically joined together.

Matter can be divided into two main categories: pure substances and mixtures.

Both elements and compounds are pure substances.

A mixture is a substance made by mixing other substances together. There are two main categories of mixtures: Homogeneous mixtures –

o Known as solutionso The parts of a homogeneous mixture are evenly distributed. Examples include a glass of dissolved

koolaid, the air we breathe, and bronze. Homogeneous mixtures of metals are called alloys. Examples include bronze, steel, and brass.

Heterogeneous mixtures – o A heterogeneous mixture is a mixture where the components of

the mixture are not uniform. The substances of the mixture are unevenly mixed.

o Examples include Chex Mix, trail mix, tossed salad, cereal in milk, granite.

You should be able to identify models of elements, compounds, mixtures:

8/20/188th grade Physical ScienceWhat You Should Know By Now:

1. Pure substance – Compound2. Mixture of elements3. Mixture of compounds and elements4. Mixture of compounds5. Pure substance – Element6. Pure substance – Compound7. Pure substance – Element8. Mixture of compounds and elements9. Mixture of elements