Mixtures, Elements, and Compounds• Mixtures – Two or more substances that are not chemically combined, and can be separated by physical means. The substances in a mixture retain their properties of their individual substance.• Elements – An element is a substance that cannot be broken down into simpler substances. It has a ﬁxed compositions because it has one type of atom.• Compounds – A compound is a substance that is made of from two or more simpler substances and can be broken down into those simpler substances (elements or compounds). A compound always contains two or more elements joined in a ﬁxed proposition.• Pure Substance – Matter that always has the exact same compositions as a pure substance. Every sample has the same properties because it has a ﬁxed uniform composition.
Homogeneous Mixture• A mixture that is the same throughout.• “well mixed.”• Particles that make up the mixture are very small and not recognizable.• Ex. Stainless steel spoon, which is a homogenous mixture because of the mixture of iron, chromium, and nickel.
Heterogeneous Mixture• In a mixture the parts are noticeably different from one another.• Comes from the Greek word hetero and genus meaning “different” and “kind”• Ex. Sand, which is a heterogeneous mixture and a stainless steel spoon, which is a homogenous mixture.
Solutions• When substances dissolve and form a homogenous mixture, the mixture that form is called a solution.• The substance that is dissolved is the solute and the substance that does the dissolving is the solvent.• Ex. Windshield wiper liquid
Suspensions• A heterogeneous mixture that separates into layers over time.• Ex: If you shake up a container of sand and water the sand mixes with the water to form a solution.
Colloids• In a colloid contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension.• Colloids do not separate into layers.• Ex. Fog is a colloid of water droplets in the air.
Physical Properties• Viscosity - How liquid ﬂows.• Conductivity - Ability to allow heat to ﬂows.• Malleability - Ability to be hammered without shatter.• Hardness - How hard an item can be hit.• Melting Point - Ability to change from solid to liquid• Boiling Point - Temperature at which a substance boils.• Density - Can be tested to ﬁnd the purity of the substance.
Separation TechniquesExamples:DecantationFiltrationCentrifugationEvaporationCrystallizationDistillationUsing a Separating FunnelFractional DistillationSublimationChromatographyMelting PointBoiling Point
Distillation• A process that separates substances in a solution based on their boiling points.• Ex. #1 B #2 U F F 100 E Plateau Temp (˚C) R 50 Plateau 0 0 Time (Min)
Filtration• A process that separates materials on the size of their particles and/or solubility.• Ex.
Evaporation• A process used to isolate a solid dissolved in a liquid: Solubility property• Ex. NaCL (sodium chloride) (table salt) + water• You will not be able to isolate pure substances of a mixture in a liquid.
Chemical Properties• A chemical property is any ability to produce a change in the composition of matter.• Chemical properties can only be observed when the substances in a sample of matter are changing into different substances.•
Evidence of Chemical Change• When matter undergoes a chemical change, the composition of matter changes. When matter undergoes a physical change, the composition of matter will retain the same.• Four types of common chemical change are... • Color change. • Temperature change. • Production of gas. • Formation of a precipitate.
Electrolysis• Electrolysis is a chemical separation technique• Notes: 2H20(liquid) -> Electricity 2H2(gas) + O2(gas), React H:1, 2:1• Hydrogen Oxygen Explosive Allow ﬂame to ignite Less dense More dense than air than air (rise) (sink) “PAP”
Question #1• At room temperature, a substance with a melting point of 40˚C is a________.
Question #2• Formation of a precipitate is usually evidence of________.
Question #3• A material that can be hit hard without shattering is an example of what property?
Question #4,5• List 1 physical change and 1 chemical change that occurs when a candle burns.• How does the composition of a mixture of hydrogen and oxygen differ from the composition containing of a compound hydrogen
Question #6• A solid, rectangular block of material ﬂoats on water. Is it possible that the block is pure gold? Explain your answer.• Suppose you mix two colorless liquids together and a green solid settles to the bottom of the container. Explain why you might be
Question #7 (Bonus)• RELATING CAUSE AND EFFECT- Explain why painting an iron railing can slow down the rate at which the railing will rust.