1.2 Properties and Changes of Matter

4 States of Matter - solid, liquid, gas, 4th state – plasma

What are Physical Properties?

•Physical properties – characteristic of matter that does not change example: melting point, color, density, state of matter (solid, liquid or gas).

Density - the amount of matter (mass) compared to the amount of space (volume) the object occupies

•Density is a physical property of matter that expresses a relationship of mass to volume. •The more mass an object contains in a given space, the more dense it is.•It’s a constant for that substance (a number that does not change)

Example: Density of Gold = 19.30 g / cm3

Question: If you cut a brick of gold in half would the Density still be 19.30 g/cm3?

Yes…. Why?

Ratio: cut mass in half – you are also cutting the volume in half

Formula:

Density = mass/volume D = m / V

•The unit for mass is grams (g) or (kg), and the unit for volume is mL or cm3 usually,

So, the units for Density are g/mL, or g/cm3

Common DensitiesDensity of water is 1.00 g/mlThe density of a material varies with temperature Usually, if temperature increases – Density decreases.Exception: Ice

Physical Properties of Matter:

1) State of matter (solid, liquid or a gas)2) Density (D = M/V)3) Malleability - ability to bend4) Ductile – ability to be drawn out into thin wires5) Melting point, boiling point, texture, color, odor

Physical Change – a change in matter that does not change the identity of individual substance.

Phase Changes are Physical Changes

Example: ice melting to water - Substance is still H2O

Clues for Physical Changes:

1) Change in shape – dissolving, cutting in half2) Phase changes – liquid to gas, melting etc

Chemical Properties and Changes

•Chemical properties –are characteristics of a material that become evident when the material undergoes a chemical reaction or chemical change. •Chemical Change - is any change that results in the formation of new chemical substances.

•Chemical Reactions describe how a substances change into other new substances.

Ex: rusting of iron, leaves changing color, burning flame, combustion of gasoline in a car engine.

Chemical Properties

1) Ability to support burning – Oxygen gas

In a Chemical Change, Matter is neither created nor destroyed:

“Law of conservation of mass and energy”

2 Mg + O2 ---- 2 MgO

2) Reactivity – also a chemical property

Ex: rusting, flammability

Clues Chemical Changes:

1) Bubbles – gas forming 2) Color Changes3) Heat changes – warm or cold

Chemical changes involve a change in energyEnergy = ability to do work Energy is either added or taken away.

Exothermic Reaction a reaction that releases energy (heat energy).

‘Exo’ – out; ‘thermic’ - heat•The container in which an exothermic reaction is taking place will feel hot.

Endothermic Reaction – reaction that takes in energy or (heat).

Endo = “into” - The container will feel cold.

Density Formula Wheel

• Formula wheels make it easy to solve density problems.

• Cover the property you are trying to find, and do what is left over.

• To find density, cover the word density. You have mass over volume remaining. So divide mass by volume to find density!

Mass

density

volume