Composition of MatterCHAPTER 15 SECTION 1HTTPS://WWW.BRAINPOP.COM/SCIENCE/MATTERANDCHEMISTRY/COMPOUNDSANDMIXTURES/

Pure Substances

A type of matter with a fixed composition or, in other words, a fixed combination

A substance can either be an element or a compound

Elements

A substance with atoms that are all alike All substances are built from atoms Graphite in your pencil point or the copper coating of most

pennies

Compounds

A substance in which the atoms of two or more elements are combined in a fixed proportion

Examples Water is a compound- two atoms of hydrogen combine with

one atom of oxygen Chalk is a compound- contains one calcium atom, one

carbon atom, and three oxygen atoms Salt is a compound- made of sodium, which is a silvery

metal, and chlorine, a poisonous gas.

Mixtures

A material made up of two or more substances that can be easily separated by physical means

Pizza and soft drinks are mixtures There are three different types of mixtures. Those are...

Heterogeneous Mixtures

A mixture in which different materials can be distinguished easily

A pizza is a heterogeneous mixture because you can easily see that there is cheese, pepperoni, and crust which are all different.

Mixtures do not always contain the same proportions of the substances that make them up

Some clothing items that are made of cotton and polyester are heterogeneous mixtures

Even though you can not see the two different fabrics with the naked eye, you can see them with a microscope

Some heterogeneous mixtures have heterogeneous mixtures within them The cheese in the pizza is a heterogeneous mixture.

Homogeneous Mixtures

Contains two or more gaseous, liquid, or solid substances that are blended evenly throughout

A soft drink is a homogeneous mixture but when the carbon dioxide fizzes, the soft drink becomes a heterogeneous mixture

Vinegar is a homogeneous mixture but is also be a solution A solution is a homogeneous mixture of particles so small that

they cannot be seen with a microscope and will never settle to the bottom of their container

Colloids

A type of mixture with particles that are larger than those in solutions but not heavy enough to settle to the bottom of their container

Examples of colloids Paint- a liquid with suspended colloid particles Fog- consists of particles of liquid water that are suspended

in air Smoke- contains solids suspended in air Fun Fact: The word Colloid comes from the Greek word for

glue and the first colloids were found in gelatin which was used in some glues

Detecting Colloids

Appearance is one way to distinguish a colloid from a substance You can tell for certain if a liquid is a colloid by passing a beam of light

through it. If the light is invisible= a solution If the light is seen readily= a colloid

Light can be seen passing through a colloid because the particles in the colloid are large enough to scatter light. Those in a solution are not. This scattering of light by particles within the colloid is called the Tyndall

Effect Examples of Colloids

Fog appears white because its particles are large enough to scatter light Some shampoos and gelatins are colloids called gels that appear almost

clear

Suspensions

A heterogeneous mixture containing a liquid in which visible particles settle

An example of a suspension would be muddy pond water If the pond water stands long enough, some mud particles

will fall to the bottom and the water will clear

Review A Pure Substance is a type of matter with a fixed composition A Substance can be an element or a compound An Element is a substance with atoms that are alike A Compound is a substance with atoms of two or more elements are combined in a

specific combination A Mixture is a material made up of two or more substances and can be easily separated A Heterogeneous Mixture is a mixture in which different materials can be

distinguished easily A Homogeneous Mixture contains two or more gaseous, liquid, or solid substances

that are evenly blended A Solution is a Homogeneous Mixture of particles that cannot even be seen through a

Microscope Colloids are a type of mixture and have particles bigger than those in solutions A Suspension is a heterogeneous Mixture containing a liquid in which the particle that

you can see can settle