Classifying Matter

ATOM Atom – the smallest unit of an element that maintains the properties of that element.

Pure Substance A sample of matter, either a single element or a single compound, that has definite chemical and physical properties Figure 14, Page 22

Elements A pure substance that contains only one kind of atom All atoms of the same element have the same atomic number

Compounds A pure substance that is made up of two or more different elements joined by chemical bonds.

Molecules The smallest unit of a substance that keeps all of the physical and chemical properties of that substance.

All of the following are molecules, but are they compounds or elements? Br2 H2O O2 O3 C12H22O12 Compound Element Element Compound

Mixtures A combination of two or more substances that are not chemically combined. Examples are air, ice tea, and even cake batter The proportions of the substances can vary

Homogeneous Mixtures have a uniform structure or composition throughout any two samples taken will have the same proportions of ingredients Examples: Gasoline, air, and syrup

Heterogeneous Mixtures NOT evenly mixed. Different regions will have different proportions Examples: Pulpy Orange Juice, chocolate chip cookie dough, and granite.

Homogeneous and Heterogeneous Mixtures

Since mixtures are just physically combined, they can be separated. Separating Mixtures Since mixtures are just physically combined, they can be separated.

Separating Mixtures Some Methods include: Filtering – separation of a mixture’s components through differences in particle size Decanting – a fancy term for separating two components by pouring Distillation – used to separate two liquids based on their differences in boiling points Magnetism – used to separate magnetic substances Evaporation – removing a liquid to leave a solid behind Centrifuge – separates substances of different densities using a fast rotational motion Chromatography – Separates two substances by using a mobile phase and a stationary phase

Physical Changes A change of matter from one form to another without changing the substance itself. A  A Examples: phase changes, mixtures

Chemical Changes when one or more substances change into entirely new substances with different properties A + B  C (reactants go to products)

An Unexpected Color Change Release or Absorption of Energy Formation of a Precipitate (solid) Formation of a gas

Chemical or Physical Frying an egg - Chemical Boiling Water - Physical Sanding a wooden plank - Physical Digesting food - Chemical Popping a balloon - Physical