Chapter 2: Matter and How It Can Change

Types of Matter Substances: contains only one type of matter and has a uniform and definite composition Element~ Composed of just one type of atom. They cannot be separated into simpler substances using chemical means. They are represented by a chemical symbol (see Periodic Table). Diatomic elements: 7 of them… start at seven, form a seven and Hydrogen. For example: Gold (Au), Iron (Fe), Oxygen (O or O2) Compound~ Substances composed of two or more different kinds of atoms. The atoms are chemically combined to form a molecule (or formula unit). They are represented by a chemical formula which shows the elements and relative number of atoms in the compound. For example: Water, H2O and Salt, NaCl.

Types of Matter Mixtures: a physical blend of two or more substances. Homogenous~ Uniform in composition. Transparent: solutions Opaque: suspensions Can be separated by distillation, ion exchange, reverse osmosis For example: Koolaid, salt water, air, milk and blood Heterogeneous~ Opaque, not uniform in composition and appearance Can be separated by sieving, tweezing and skimming For example: Sand, bronze, us and the ocean

States of Matter Solid~ Liquid~ Gas (Vapor)~ Plasma~ Definite shape and volume Very slight thermal expansion and almost incompressible Divided into subclasses of amorphous (or glassy) solids and crystalline solids Arrangements of atoms or molecules in crystalline solids are repeated regularly over a very long range of millions of atoms Arrangements in amorphous solids are somewhat random or short range of say some tens or hundreds of atoms. Liquid~ Indefinite shape (flows) and definite volume Moderate thermal expansion and almost incompressible Gas (Vapor)~ Indefinite shape and indefinite volume Great thermal expansion and readily compressible A vapor is the gaseous form of a substance that is normally solid or liquid at room temperature Plasma~ A very hot state of matter where atoms have been ripped apart into their smaller parts, protons and electrons.

Animation

Properties of Matter Everything is made of matter Mass is the amount of matter (grams or kg) Volume is the space that the matter takes up (cm) Two main types: Physical properties: A characteristic of a substance that can be measured or observed without changing the substance’s composition Intensive-don’t change for a particular sample such as density, melting point, boiling point, color, solubility conductivity, ductility, and specific heat. Extensive- depend on size of matter such as length, mass, height, volume, and area. Chemical properties: A characteristic of a substance that describes how it interacts with other substances to become something new.

Changes in Matter Physical Change Chemical Changes An alteration of matter that does not change the chemical composition of the material For example: freezing or melting, boiling or condensing, cutting, grinding, bending, blending Chemical Changes Results in a change in the chemical composition of the substance(s) which is called a reaction. For example: rusting, composting, tarnishing

Practice Identifying Types of Changes in Matter Chemical Physical Physical Chemical Physical Chemical Physical Chemical

Chemical Reactions In a chemical reaction, one or more substances change into new substances by rearranging the atoms Copper + nitric acid  copper(II) nitrate + nitrogen dioxide + water Reactants  Products The ability of a substance to undergo a chemical reaction and form new substances is called a chemical property. How to tell a chemical reaction has occurred. Heat is absorbed or given off. Change in color or odor. Production of a gas or solid. Law of Conservation of Mass During any chemical reaction, mass is neither created nor destroyed. The total mass of the system (products plus reactants) and the mass of each element is unchanged. Chemical Reaction Movies