What’s the MATTER, part II

Types of Matter Pure Substance- Matter with a fixed composition It has distinct properties Examples = elements compounds

Mixtures- Most matter is a mixture The composition is not fixed (changes from sample to sample) Two Types – Homogeneous Heterogeneous

Homogeneous Mixtures Composition is uniform throughout True Solution- (typically transparent) Particle size = 0.01 – 1 nm Doesn’t settle out upon standing Can’t be separated by filtering Doesn’t scatter light Example = distilled water

Heterogeneous Mixtures Colloid- (typically translucent /opaque) Particle size = 1 – 1000 nm Doesn’t settle out upon standing Can’t be separated by filtering Scatters light (Tyndall Effect) Examples = milk, gelatin, smoke

Heterogeneous Mixtures Suspension The sample varies in composition, properties and appearance No Tyndall Effect Particle size is greater than 1000 nm Particles settle out upon standing Can be separated by filtration Might scatter light Examples = soil, trail mix, pond water

Physical vs. Chemical Properties Every substance has a unique set of properties (characteristics that identify that substance) Physical Properties- Properties that can be measured without changing the identity and composition of the substance

Physical Property Examples- Color Odor Density Melting Point Boiling Point Hardness Solubility

Physical Change A change in matter from one form to another without changing its chemical properties (most can be reversed) Examples = Mixing Dissolving Compressing Evaporating Cutting Change in State

Chemical Properties Properties that describe the way a substance may change to form other substances Only observed when a chemical reaction takes place

Chemical Property Examples Heating to combustion Reactivity with water or acid Flammability Corrosion Decomposition

Law of Conservation of Mass In a physical change or a chemical reaction, mass is neither created or destroyed (Antoine Lavoisier)

Signs of a Chemical Reaction Chemists Get Practice Trying Labs Color Gas / Bubbles Precipitate Temperature Endothermic = cold Exothermic = hot Light