Chemistry 8 — Matter, Energy & States of Matter

Matter

Anything that has mass and takes up space.

Chemistry

The study of matter, its properties, and how it changes.

Mass

Amount of matter in an object.

Weight

Force of gravity acting on an object.

Volume

Amount of space an object takes up.

Density

How much mass is packed into a certain volume.

Density formula

Density = Mass ÷ Volume.

Mass formula

Mass = Density × Volume.

Volume formula

Volume = Mass ÷ Density.

Less dense than a liquid

Floats.

More dense than a liquid

Sinks.

SI unit for mass

Kilogram (kg).

1 kilogram

1,000 grams.

1 gram

0.001 kilograms.

Volume units

mL, L, cm³, m³.

1 liter

1,000 mL.

1 mL

1 cm³.

Weight unit

Newton (N).

Temperature units

°C or K.

Length unit

Meter (m).

Time unit

Second (s).

Physical change

Changes form or appearance without making a new substance.

Physical change examples

Melting ice, freezing water, breaking glass, dissolving sugar.

Chemical change

Produces one or more new substances.

Chemical change examples

Rusting iron, fruit ripening, silver tarnishing, burning.

Element

Pure substance made of one type of atom.

Atom

Smallest unit of an element.

Molecule

Two or more atoms chemically bonded together.

Compound

Two or more different elements chemically bonded together.

Mixture

Substances physically combined but not chemically bonded.

Chemical bond

Force that holds atoms together.

Chemical formula

Symbols and numbers showing which atoms are in a substance.

H₂O

2 hydrogen atoms and 1 oxygen atom.

CO₂

1 carbon atom and 2 oxygen atoms.

Electrolysis

Using electricity to break a compound into simpler substances.

Combustion

Burning; usually reacts with oxygen and releases energy.

Oxidation

Chemical reaction involving electron loss; often involves oxygen.

Rusting

Example of oxidation.

Tarnishing

Metal reacts and forms a new substance on its surface.

Temperature

Average energy of motion of particles.

Thermal energy

Total energy of all particles in an object.

Chemical energy

Energy stored in chemical bonds.

Heat transfer

Thermal energy moves from warmer matter to cooler matter.

Endothermic

Absorbs energy.

Endothermic examples

Melting, vaporization, sublimation.

Exothermic

Releases energy.

Exothermic examples

Freezing, condensation, deposition, combustion, hand warmers.

Melting

Solid → liquid.

Freezing

Liquid → solid.

Vaporization

Liquid → gas.

Condensation

Gas → liquid.

Sublimation

Solid → gas.

Deposition

Gas → solid.

Law of conservation of mass

Matter is not created or destroyed during ordinary physical or chemical changes.

Crystalline solid

Particles arranged in a regular, repeating pattern.

Crystalline examples

Salt, sugar, diamond.

Amorphous solid

Particles arranged randomly with no repeating pattern.

Amorphous examples

Glass, plastic, rubber.

Fluid

A substance that can flow.

Liquids and gases

Both are fluids.

Liquid

Has a fixed volume but takes the shape of its container.

Gas

Has no fixed shape or volume and fills its container.

Viscosity

A fluid’s resistance to flowing.

High viscosity

Flows slowly; more resistance. Example: honey.

Low viscosity

Flows easily; less resistance. Example: water.

Pressure

Force pushing on a certain area.

Pressure formula

Pressure = Force ÷ Area.

Pressure symbol

P = F ÷ A.

Pressure unit

Pascal (Pa).

Easy memory

Matter = stuff; Mass = amount of stuff.

Easy memory

Crystalline = organized; Amorphous = random.

Easy memory

ENDO = energy enters.

Easy memory

EXO = energy exits.

Easy memory

Temperature = average; Thermal energy = total.