Classification of Matter I. Describing Matter Physical Property General Property Chemical Property Physical Change Chemical Change

A. Physical Property A characteristic of a substance that can be observed or measured without changing its identity. can be used to separate mixtures Viscosity- resistance to flowing Greater viscosity, slower it moves Honey vs. water Decreases when heated

Physical Properties Conductivity- ability to conduct heat Metals have high conductivity-wood bad Usually good conductors of electricity Malleability- ability of a solid to be hammered without shattering Most metals are malleable Hardness- the resistance of a substance to scratching Knife (stainless steel) & diamonds

Physical Properties Melting Point- temperature at which a solid turns to a liquid Boiling Point- temperature at which a liquid turns to a gas Density- mass per unit volume

Why do we use Physical Properties? Identification of unknown substances: -Crime scenes -Chemists, researchers Choosing the right material: -frying pan- use metal, not wood Separating mixtures: -filtration- process that separates materials based on the size of the particles -distillation- process that separates substances in a solution based on their boiling points Ex. Converting sea water to fresh water BP salt= 1465 C BP of water= 100 C

General Properties of Matter All objects have these 4 properties: 1. Mass- amount of matter in an object -g 2. Volume- amount of space an object takes up -L, mL, and cm3 3. Density- the amount of matter in a given space -D=m/v -g/mL or g/cm3 4. Weight- the force of gravity acting on an object - W=mg = kgm/s2 = N

Weight Ex) A student’s weight is 694 N on Earth. What will her weight be on the moon if the moon’s gravity is 1/6th that of the Earth’s? W= mg W mg Given: W = 694 N m= W/g m= 694 N / 9.8 m/s2 = 71 kg g = 9.8 m/s2 on Earth g on moon = (9.8 m/s2)(1/6)=1.6 m/s2 W=mg W= (71 Kg) (1.6 m/s2) = 110N

Chemical Property Any ability to produce a change in the composition of matter Change into a new substance 1. Flammability- ability to burn-paper, gas 2. Reactivity- how readily a substance combines chemically with other substances -oxygen- highly reactive-reacts with iron & water to form rust

Classes of Matter Elements, Compounds, Mixtures A. Pure Substances: Elements- simplest pure substance -homogeneous (same) -can’t be split or changed into simpler substances -Ex. Oxygen, Nitrogen, Copper atom- smallest particle of an element -made up of subatomic particles a) all elements are made up of atoms b) atoms of the same element are the same c) atoms of different elements are different chemical symbol- a shorthand way to represent an element - H, O, N , Cu

2. Compound matter composed of 2 or more elements in a fixed ratio-chemically combined properties differ from those of individual elements Ex. Water= H fuels fire, O keeps it burning Can be broken down by chemical means (heat, electric current, etc.) EX: salt (NaCl), sugar (C12H22O11), H2O

Molecule- smallest particle of a Molecule- smallest particle of a compound that has the properties of the compound -some elements exist as diatomic molecules -H2, O2, N2, Cl2, F2

Chemical Formulas Combination of chemical symbols Symbols of the kind of elements in a compound # of atoms of each element Ex) H2 = 2 atoms of Hydrogen 2– subscript H2O = 2 atoms of Hydrogen, 1 atom Oxygen H2SO4= 2 atoms of Hydrogen, 1 atom Sulfur, 4 atoms of Oxygen Coefficient- the # in front of the symbol or compound – tells how many molecules Ex) 2H2O = 2 molecules of water -each contains 2 atoms of H, 1 atom O 2(H2O) = Total of 4 Hydrogen and 2 Oxygen a) 4HCl b) 4H2SO4 c) (NH3)2 d) (H2O)2

3. Mixtures 2 or more pure substances mixed together. No chemical combination or rxn No new substances are formed Have properties of substances forming it: Salt water= salty & wet Homogeneous Mixture (Solution) even distribution of components very small particles Cannot be filtered or scatter light particles never settle EX: saline solution, alloy-metal solution-solid dissolved in solid Brass= copper + zinc

3. Mixtures Heterogeneous mixtures: Uneven distribution of components- EX: granite Colloids & suspensions Suspension large particles particles scatter light, can be filtered particles will settle (needs to be shaken) EX: fresh-squeezed lemonade, saw dust in air

C. Mixtures Colloid medium-sized particles particles scatter light (looks cloudy), cannot be filtered particles never settle EX: milk, fog-water droplets in air

Can it be separated by physical means? A. Matter Flowchart MATTER yes no Can it be separated by physical means? MIXTURE PURE SUBSTANCE Is the composition uniform? no yes Can it be decomposed by chemical means? no yes Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element

B. Physical Change A change in the form of a substance without changing its identity. properties remain the same Some are reversible can be used to separate mixtures EX: dissolving, grinding, cutting paper, cut/braid hair, freeze water

C. Chemical Change A change in the identity of a substance. properties change one or more new substance is formed irreversible Signs: a) color change (patina) b) formation of a gas- baking soda + vinegar- carbon dioxide c) release of light/heat – d) precipitate- solid that forms & separates from a liquid- lemon juice + milk- curdles EX: burning, rusting