Chemistry Unit 1 Study Guide – Flashcards

Three states of matter: solid, liquid and gas. -Solid: constant shape, constant volume, particles bound together rigidly. -Liquid: variable shape, constant volume, particles bound togetehr but flexibly. -Gas: variable shape, variable volume, particles not bound together.

Element: a substance that cannot be separated or broken down into simpler substances by chemical means; all atoms of an element have the same atomic number. (are pure substances that contain only one kind of atom). Molecules: the smallest unit of a substance that keeps all of the physical and chemical properties of that substance; it can consist of one atom or two or more atoms bounded together. (usually consists of two or more atoms combined in a definite ratio). Pure Substance: a sample of matter, either a single element or a single compound, that has definite chemical and physical properties. (every pure substance has characteristic properties that can be used to identify it). Compounds: a substance made up of atoms of two or more different elements joined by chemical bonds. (compounds are composed of more than one kind of atom). Mixture: a combination of two ore more substances that are not chemically combined. (a sample of matter that contains two or more pure substances). 1. Homogenous: the particles are evenly distributed the particles will not separate over time does not diffract light called a solution. 2. Heterogeneous: the particles are NOT evenly distributed. Suspensions will separate over time (oil & water) Colloids are stable heterogeneous mixtures that will NOT separate over time.

-Chemical Properties: are properties of an element or compound in chemical reactions. -Physical Properties: are properties of an element or compound that can be observed without a chemical reaction of the substance.

-Physical changes: Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle. Chemical changes: Chemical changes take place on the molecular level. A chemical change produces a new substance. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water.