Chem 20 Review Unit 1

science- the study of the natural and technological world to describe, explain, and predict substances and charges

chemistry- the physical science that deals with the composition, properties, and changes in matter: the study of chemicals and their reactions, associated technologies and environmental effects.

Empirical knowledge-knowledge gained through observations

generalizations-a statement that summarizes a limited number of empirical results

Scientific Law- a major empirical concept that is based on a large body of empirical knowledge

Empirical Hypotheses- a preliminary generalization, regarding observable properties that require further testing

Empirical Definitions- a statement that defines an object or a process in terms of observable properties

Theoretical Knowledge- knowledge that explains the unobservable through scientific observation

Matter- anything that has mass and occupies space; may be a pure substance or a mixture

Pure Substances- matter whose composition is constant and uniform; composed of only one kind of chemical

Mixture-matter whose composition includes 2 or more substances and may or may not be uniform throughout the sample

Elements- a pure substance that cannot be broken down into simpler chemical substances by only physical or chemical means; consists of only one kind of atom.

compounds- a pure substance that can be separated into its elements by heat, or electricity; a substance containing atoms/ions of more than one element in a definite fixed proportion.

Atom- the smallest entity of an element that is still characteristic of that element

Periodic Law- the observation that chemical and physical properties of elements repeat themselves at regular

Metal- an element that is shiny, bendable, and a good conductor of electricity

Nonmetal- an element that is not shiny, not bendable, and generally not a good conductor of electricity.

Semimetals- a class of elements that are distributed along the “staircase line” in the periodic table; also called metalloids

Akali metals- a soft, silver-coloured metal that reacts violently with water. Group 1 elements

alkaline-earth metals- a light, reactive metal that forms an oxide coating when exposed to air. Group 2 elements

halogens- a reactive non-mental element from group 17

noble gases- a very unreactive gaseous element from group 18; an element with a full shell of valence electrons

Theory- a concept or set of ideas that explains a larger number of observations in terms of non-observables

Mass Number- the sum of protons and neutrons in the nucleus of an atom or nonatomic ion.

Atomic Number- the characteristic number of protons in the nucleus of an atom of a particular element

Ion- an entity with a net positive or negative electrical charge due to the loss or gains of one or more electrons

Cation- a positively charged ion

anion- a negatively charged ion

ionic compound- a pure substance formed from a metal and a nonmetal

molecular compound- a pure substance that may be a solid, liquid, or gas at SATP. Consists of covalently bonded nonmetal atoms

Acid- a compound that forms electrically conducting aqueous solutions that turn blue litmus red, neutralize bases, and react with active metals to produce hydrogen gas

Aqueous Solution- a homogenous mixture of one or more solutes dissolved in water.

Polyatomic Ion- a group of atoms with a net positive or negative charge on the whole group

Hydrate- a pure substance that decomposes at a relatively low temperature to produce water and other substances in a substance containing loosely bonded water molecules.