Chapter 2: Properties of Matter

Matter – has mass takes up space

Can be classified as a substance or mixture

Substance vs. Mixtures

Substance Mixture A substance always has the same

composition

Every sample has the same properties

Two types are Elements and Compounds

Properties can vary because the composition in not fixed

Classified by how well the parts are distributed

Two types are heterogeneous and homogeneous

Substances

Element Compound A substance that

cannot be broken down

An atom is the smallest particle

Fixed composition because it contains only one type of atom

Made from two or more simpler substances

Can be broken down Properties are

different than those it is made of

Contains elements in a fixed proportion

Mixtures

Heterogeneous Homogeneous The parts are different Evenly distributed so

difficult to distinguis Appears to contain

only one substance

Now it is your turn… you tell me: Homogeneous or Heterogeneous

Flat soda pop Cherry vanilla ice cream Sugar (C2H3O2) Salt (NaCl) City Air Iron (Fe) Beach Sand Spaghetti Sauce

Mixtures can also be classified by their largest particle

Solutions When dissolves and forms a homogeneous mixture Cannot be filtered

Suspension A heterogeneous mixture that separate into layers

over time Settle out or filtered out Are cloudy

Colloids Particles of intermediate size Do not separate Cannot filter

Physical Properties

A physical property is any characteristic that can be observed or measured without changing the composition

Examples: Viscosity Conductivity Malleability Hardness Melting/Boiling Density

Physical Properties Viscosity

Resistance to flowing The greater the viscosity the slower the

liquid moves Usually decreases when heated

Conductivity Ability to allow heat to flow Materials with high conductivity are

conductors

Malleability

Can be hammered Most metal are malleable Solids that shatter when struck are

brittle

Hardness

One way to compare is to see which can scratch the other

Diamond is the hardest known material

Melting/Boiling

Melting: changes from a solid to a liquid

Boiling: temperature a which it boils

Density

Can be used to test the purity Ratio of mass to its volume D = Mass/Volume

Physical Properties

Are used to identify a material, to choose a material for a specific purpose, or to separate the substance

Separating Mixtures (2 Ways) Filtration – process that separates based

on the size of their particles Distillation – process the separates bases

on boiling points

Filtration vs. Distillation

Physical Changes

Occurs when some of the properties of a material change but the substance in the material remains the same.

Ex. Melting Butter, Crumpling Paper, Slicing

Some can be reversed ( melting, boiling)

Chemical Properties Is any ability to produce a change in

the composition of matter Can be observed only when the

substances are changing into different substances

2 Examples Flammability

Is a materials ability to burn in the presence of oxygen

Sometimes is not a desirable property

Reactivity – Example of Chemical Property

Describes how readily a substance combines chemically with other substance.

Recognizing Chemical Changes A chemical change occurs when a

substance reacts and forms one or more new substances.

Ex. 1. Change in Color2. Production of a gas3. Formation of a precipitate

Evidences of Chemical Change 1. Change in Color

Is a clue that a chemical change has produced at least one new substance

2. Production of a Gas Bubbles can show a chemical change (ex.

Cake)3. Formation of a Precipitate

Any solid that forms and separates from a liquid

Chemical or Physical?

Even if you observe a color change, a gas, or a precipitate you cannot be sure

Ask yourself???

Are different substances being formed???-If yes then is chemical!