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-  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

Homogenous Mixtures Colloid-  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 uniformity  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  If sample is layered = suspension

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 identity (most can be reversed)  Examples = Change in state Dissolving Compressing Mixing Cutting

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