EOG Review Notes Chemistry 8.P.1

8.P.1.1 Classify matter as elements, compounds, or mixtures based on how the atoms are packed together in arrangements.

Big Picture Elements are pure substances with only ONE type of atom. Most matter is a combination of elements Atoms  elements  molecules  compounds Vocab terms: compound, molecule, chemical formula, subscript, ionic bond, covalent bond

The ATOM The center of the ATOM is the NUCLEUS The NUCLEUS is responsible for the MASS of an ATOM. ATOMS are made up of three SUBATOMIC PARTICLES: PROTONS, NEUTRONS, and ELECTRONS

Atomic Structure PROTONS: POSITIVELY charges particles (+) NEUTRONS: Uncharged or NEUTRAL particles ELECTRONS: NEGATIVELY charged particles (-) PROTONS and NEUTRONS are always found together in the NUCLEUS of an ATOM and the ELECTRONS will always orbit around the NUCLEUS

The Element An element is one type of atom, it can not be broken down Into something else.

Molecules Def: A group of atoms held together by a covalent bond. Molecules: Compounds Atoms: Elements Compounds and molecules are often expressed as chemical formulas: Chemical formulas use symbols and subscripts to identify the number of atoms of each element in a compound

Compounds 2 or more elements Compounds usually have very different properties than the elements that compose them 3 important characteristics: have a definite composition can be broken down into simpler substances by chemical means can be identified by their physical properties

Determine the valence # by group # The valence number is the number of electrons in the outer energy level of an atom. It tells us the ability of an element to bond with other elements

Period Table of Elements

Solutions are Mixtures MIXTURE: combinations of substances, like a salad. Easily separated into basic components. SOLUTION: type of mixture that can not be separated. Solutions are blended together so well that they become one. Known as a homogenous mixture.

Parts of a Solution Solutions have two definite components: SOLUTES: the substance that is dissolved to make a solution; the solute dissolves and is usually the smaller component SOLVENT: the substance that dissolves the solute; usually the larger component Ex: Kool- Aid Solute (sugar) + Solvent (water) = SOLUTION (Kool- Aid)

Types of Solutions 3 types of solutions: Gas Solution: air around you is a solution! Solid solution: bronze is a metal solution consisting of tin dissolved in copper Liquid Solution: tap water contains many dissolved substances

Suspensions In a SUSPENSION, the particles are larger than those found in the solution; instead of dissolving the particles turn the mixture cloudy. Ex: Flour in water Suspensions can be easily separated. How could this solution be separated?

Mixtures Heterogeneous mixture Homogeneous mixture

Changing Properties Adding a solute will: Lower the FREEZING POINT (the temperature at which a liquid turns into a solid) Raises the BOILING POINT (the temperature at which a liquid turns into a gas)

Chemical or Physical Change? A PHYSICAL CHANGE is a change that does not change the structure of molecules. Ex: melting ice, tearing paper, sharpening a pencil A CHEMICAL CHANGE occurs when a substance is changed into another substance. Ex: a precipitate forms, a gas forms, color changes, temperature change