Chapter 2

anything that occupies a volume of space and has mass.

Some Greek philosophers believed all matter was continuous

The fundamental model of matter

• Physicists measure the diameter of a typical particle of matter in nanometers • There are different kinds of particles of matter, but most common particle that scientists refer to is the atom

a distinct particle formed when two or more atoms bond together and become separate from other atoms

Particles with unbalanced electrical charges

Materials made of only one kind of substance • Elements • Compounds

Mixing two or more substances together • Homogeneous • Heterogeneous

We normally find matter on Earth in one of three physical forms, or states: solid, liquid, or gas

• Solid materials make up most of the earth’s physical objects • Do not easily change shape • Do not flow • Volume is basically constant

• Definite volume * Flow

• No definite shape • No definite volume • Flow • Molecules are far apart and move at high speeds

• Anything about a substance or object that we can observe or measure without changing its chemical composition

• Can affect shape or state of the material • Does not change its chemical composition

• Melting: change from solid to liquid • Temperature: melting point • Freezing: change from liquid to solid • Temperature: freezing point

• Any process resulting in a solid or liquid substance changing directly to gas • The rate of vaporization refers to how fast liquid water changes to a gas • Vapor pressure

• Boiling • Evaporation * Sublimation

vapor cools and changes to liquid

vapor becomes a solid

Materials can change from one kind of chemical substance into other kinds of chemical substances

• Contains protons, electrons, and usually neutrons • Center of the atom is the nucleus • Contains one or more protons • Electrons are found around the nucleus