Matter and Changes in Matter Dr. Childs Fall, 2005 Science Laboratory

Matter

Matter Matter is everything that we see and many of the things we don’t see (as air). By definition matter has mass and occupies space. Matter is classified into two major categories: - Pure substances - Mixtures Brass (mixture of copper & zinc) Pure silver

Matter Matter can be changed. These changes may involve physical changes in which the composition of the matter is not changed or chemical changes in which the composition is changed. Candle burning Ice melting

Pure Substances Pure substances: - contain the same type of particles throughout. - have a definite composition. - may be either elements or compounds - sodium chloride NaCl sodium Na chlorine Cl

Types of Matter

Elements & Compounds

Elements & Compounds An element is a pure substance that cannot be broken into anther substance (by ordinary chemical means). Composed of only a single type of atom. A compound is a pure substance composed by two or more elements How about some examples?

Elements Many things are made of elements. For example, aluminum is used for foil and for building cars and trailers. Note: If its on the periodic table its an element!

Elements Sulfur Gold Lead Oxygen Hydrogen fuel Sodium lamp

Elements magnesium wheels silicon sealant chromium wheels lithium grease titanium clubs carbon fiber

Compounds Compounds are formed when two or more atoms of two or more elements combine chemically (bonding!). - fixed ratio of elements with a definite formula - separation into elements requires chemical procedures Water H2O Note: Compounds are NOT on the periodic table.

Compounds table sugar C6H12O6 table salt NaCl Carbon dioxide Nitrous oxide N2O Sodium hydroxide NaOH rust Fe2O3 Epsom salts MgSO4

Mixtures

Mixtures Mixtures are materials made up of two or more pure substances. Mixtures can be separated by physical means based on physical properties: evaporation filtration floating magnets Mixtures may be either homogeneous (solutions) heterogeneous

Mixtures

Mixtures Homogeneous mixture of metal are “alloys”. Alloys include brass, steel, and white gold. Homogeneous mixtures in which one substance is dissolved in another is a “solution”. Solutions include coffee, IV fluids, and fog.

Homogeneous Mixtures Examples: Sea water water and salt Coffee coffee, sugar, cream Blood red cells, white cells, plasma Air nitrogen, oxygen, CO2 Brass copper, zinc White gold gold, silver, platinum

Homogeneous Mixtures Corn flakes Brass Coffee jello Salt water colored Blood

Heterogeneous Mixtures Examples: raisin bran cereal with raisins chocolate chip cookie tossed salad lettuce, tomatoes, carrots pizza pizza with meat, cheese granite feldspar, mica Italian dressing oil, water, spice

Heterogeneous Mixtures Italian dressing Raisin Bran Tossed salad Chocolate Chip cookie Granite Marble Muddy water

Separating Mixtures filtration evaporation salt ponds evaporation distillation

Separating Mixtures chromatography electrophoresis centrifugation

Physical and Chemical Changes

Physical & Chemical Properties Be sure to know the difference between: - Physical properties & chemical properties - Physical changes & chemical changes

Physical Properties Physical properties can be observed without a chemical reaction. Examples: color: water is clear, table salt is white density: aluminum has a density of 2.7 g/cm3 state: oxygen is a gas at room temperature magnetism: iron is attracted to magnet texture: gold is shiny

Physical Properties What are some physical properties of: sulfur? lemonade? dish soap?

Physical Changes In a physical change substances are not altered chemically, including: state changes solid  liquid liquid  gas mixing or separating adding sugar to coffee evaporating sea water for salt tearing paper

Physical Changes State Changes liquid  solid “freezing” water to ice liquid  gas “evaporation” water to steam gasoline to vapor solid  gas “sublimation” dry ice to CO2 sublimation freezing evaporation

Physical Changes State Changes solid  liquid “melting” ice to water ice cream melting gas  liquid “condensation” ice to water condensation melting

Physical Changes Physical changes may involve changing shape but not composition; Breaking glass Sawing wood Planing wood

Chemical Properties Chemical properties: The properties of an element or compound in a chemical reaction Examples: gasoline is flammable water can be separated by electrolysis neon is inert

Chemical changes Chemical reactions: - yield new substances - usually cannot be easily reversed - may either require or release energy (light, heat, etc.) Sugars in wood may be split by burning. Combustion yields new substances: CO2 and water and heat and light energy.

Chemical Changes Candle burning Fireworks Toasting bread Combustion Digesting food

Chemical Changes bread rising photosynthesis food cooking batteries rusting

The End