What’s the Matter? Introduction to Chemistry Ch. 2.1-2.4

Chemistry and Matter Chemistry is the study of matter and the changes it undergoes. Matter is anything that takes up space and has mass. Mass - the amount of matter in an object. Volume – the amount of space the object occupies.

Properties of Matter Extensive Property: Depends on the amount of matter in a sample. Ex. Mass, volume, length Intensive Property: Depends on the type of matter in a sample, not the amount. Intensive properties can be used to identify a substance. Ex. Density, hardness, melting point, boiling point

Physical and Chemical Properties of Matter A physical property is a property that can be observed or measured without changing the chemical composition of the substance. Ex: Melting point, freezing point, density, color, conductivity A chemical property is the ability of a substance to undergo a specific chemical change. Chemical properties can be observed only when a substance undergoes a chemical change. Ex: Flammability, ability to rust, reactivity with water

Physical and Chemical Changes Physical change: Change in which the composition of the material does not change. Ex: melt, evaporate (phase changes), tear, crush, break, grind Chemical change: Change in which the chemical composition of the material changes. Ex: burn, explode, decompose, rot, rust, corrode

Indicators of a Chemical Change Color change Bubbles (indicates a gas is produced) Formation of a precipitate (solid that forms and settles out of a liquid) Temperature change

States of Matter Solid Liquid Gas Notice: There are 12 “particles” in each state of matter. During a phase change, the number of particles stays constant.

States of Matter Solid Liquid Gas Particle movement Shape Volume Easily Compressed? Solid Vibrate in fixed positions Definite No Liquid Particles close together but flow past one another Indefinite - Takes shape of container Gas Particles far apart and move freely Indefinite- Takes shape of container Indefinite Yes Vapor: A term used to describe the gaseous state of a substance that is generally a solid or liquid at room temperature. (Ex. Water vapor)

What Happens When You Increase the Temperature of a S, L, and G? Solid – particles vibrate faster, increasing kinetic energy. The solid expands slightly. Liquid – particles move faster, increasing kinetic energy. The liquid expands slightly. Gas – particles move faster, increasing kinetic energy. The gas can expand greatly. Kinetic energy: The energy of motion. ↑ particle movement, ↑ KE

Matter can be Classified as a Substance or a Mixture A pure substance is matter which has a uniform and definite composition. Pure substances can be classified as elements or compounds. An element is the simplest form of matter that has a unique set of properties. Ex. Cu, C, Al Elements cannot be broken down into simpler substances. A compound is a substance made of two or more different elements chemically combined. Ex. CuCl2, H2O, CO2 Compounds can be broken down into simpler substances (elements) by chemical means.

Matter can be Classified as a Substance or a Mixture Compounds generally have properties that are different from the elements that make them up. Ex. Salt (sodium chloride), NaCl Sodium, Na Chlorine, Cl Salt, NaCl

Mixtures A mixture is a physical blend of two or more components. Mixtures can be classified as homogeneous or heterogeneous. Mixtures can be separated by physical means.

Mixtures Homogeneous mixture: Mixture that is uniform (the same) throughout. Homogeneous mixtures are also called solutions. Ex: Kool-Aid, salt water Heterogenous mixture: Mixture that is not uniform throughout. You can pick out the individual components. Ex. Salad, chicken noodle soup

Separating Mixtures Use physical properties What physical properties could be used to separate iron filings from table salt? What physical properties could be used to separate sand from water? What physical properties could be used to separate alcohol and water?

Separating Mixtures What physical properties could be used to separate iron filings from table salt? Use a magnet, iron is magnetic, salt is not What physical properties could be used to separate sand from water? Use a filter, sand is a solid, water is a liquid What physical properties could be used to separate alcohol and water? Use distillation, alcohol and water have different boiling points

Separation Techniques Distillation Filtration Separates liquids based on Separates solids from liquids boiling point. Can also separate solids from liquids by evaporation.

Chemical Symbols and Formulas Chemists use chemical symbols to represent elements. Ex. P = phosphorus Chemists use chemical formulas to represent compounds. Ex. H2O = water

Writing Chemical Reactions Reactants: what you start with Go on the left side of the arrow Products: what you end up with Go on the right side of the arrow Example: 2H2 + O2 2H2O product reactants

Law of Conservation of Mass (LOCM) Law of Conservation of Mass: Mass (matter) can neither be created nor destroyed in any physical change or chemical reaction. Mass is conserved. In other words, the mass of the reactants is equal to the mass of the products.