Properties of MatterChapter 2

Classifying Matter2.1

Types of Matter

Pure Substances Elements Compounds Mixtures Solutions, Suspensions and Colloids

Pure Substances

Matter that always has exactly the same composition

Every sample of a substance has the same properties because a it has a fixed composition.

Ex: salt, sugar, flour 2 Types

1. Elements2. Compounds

Elements

Cannot be broken done into simpler substances

fixed composition because contains only one type of atom

No two elements contain the same type of atom

Atom = smallest particle of an element

Element Example

Gold

Aluminum

Carbon

Sodium

Compounds

Made from two or more simpler substances

Contains two or more elements in a fixed proportion

Can be broken down into its simpler substances (either elements or other compounds)

Properties of a compound differ from those substances from which it is made

Compound Examples

Sodium Chloride

Sodium: soft, highly reactive metal Chlorine: greenish colored gas, can

be toxic

Compound Examples

Liquid Petroleum Gas (mixture of propane and butane gas)

Made-up of carbon and hydrogen. Both gases More reactive than diesel, thus spark

ignition

Compound Examples

Petrol Diesel (mixture of hydrocarbons) Made up of carbon and hydrogen Both Gases Does not burn as easily as gasoline thus

air is compressed in cylinder and creates higher temperatures

Summary

Pure Substances: same properties, uniform composition

Elements:Fixed composition, contains one type of atom

Compounds: two or more elements in a fixed proportion

Mixtures

Properties of mixtures can vary because the composition is not fixed

2 Types: Heterogeneous and Homogeneous

Heterogeneous Mixture

Parts of mixture are different from one another Ex: salsa, salad, sand

Hom0geneous Mixture

Substances are so evenly distributed it can hard to distinguish them Ex: stainless steel, made of iron, chromium and

nickel Swimming pool, water at the shallow end is the

same as the water at the deep end

Solutions, Suspensions , Colloids

Size of particles in a mixture effect the properties

Based on the size of the largest particle a mixture can be classified as a solution, suspension or a colloid

Solutions

When substances dissolve and form a homogeneous mixture Ex: tap water, lemonade

Can see light through these solutions Particles are small so light passes

through without being scattered in all directions

Particles will not settle out but can be filtered out

Solutions

Suspensions

Heterogeneous mixture that separates into layers over time

Suspensions are cloudy because larger particles can scatter light Ex: Muddy water, sawdust in air

Suspensions

Colloids

Contains some particles that are intermediate (between solution and suspension)

Do not separate into layers Cannot filter out particles Scatters light

Ex: Fog, milk

Colloids

Physical Properties2.2

Physical Properties2.2

Physical Properties

Characteristic that can be observed or measured without changing the composition (make-up) of a substance

Viscosity, conductivity, malleability, hardness, melting point, boiling point and density

Viscosity

Resistance to flowing Greater the viscosity the slower the

liquid Thin liquids have a low viscosity

Ex: Honey vs. soda Heating up a liquid lowers its

viscosity Ex: oil

Conductivity

Ability to let heat flow Materials with high conductivity are

called conductors Ex: Metals

Hardness

Resistance to scratching The hard the material the less likely

it can be scratched and the more likely it will scratch something else Ex: Diamond Drill Tips

Melting and Boiling Points

Melting Point: temperature a substance goes from a solid to a liquid

Boiling point: temperature at which a substance boils

Density

Amount of matter in an object Ratio of the mass to volume Different substances have different

densities

D = M/V

Using Physical Properties

Used to identify materials Choose materials for a specific

purpose Separate materials in a mixture

Filtration and Distillation

Filtration

Separates materials based on size of particles

Distillation

Separates substances based on their boiling points

Physical Changes

Occurs when some properties of the material change but not the composition

Some are reversible, some are not

Chemical Properties2.3

Chemical Changes

Chemical Property: ability to produce a change in the composition of matter

Observed only when substances are changing into different substances Ex: Flammability and Reactivity

Flammability

Materials ability to burn in presence of oxygen

Reactivity

How easily a substance combines chemically with another Ex: Rust (oxygen and iron) Ex: Water and baking soda

Chemical Changes

Chemical Change: when a substance changes from one form to another

Evidence of Chemical changes:1. Change in color2. Production of gas3. Formation of a precipitate (a solid that

forms)