Matter and Change Ch. 2

Matter 2-1

Are the following considered matter? Key Terms Chemistry: explains the structure and properties of matter Matter: anything that occupies space and has mass Mass: amount of matter an object contains Are the following considered matter? Car, pencil, heat, thoughts/ideas, light, air, radio waves, water, cell

States of Matter Most common states of matter: Solid: particles in fixed position, tightly packed; definite shape and volume. Liquid: particles tightly packed but can slide past each other; fixed volume but changing shape. Gas: particles in constant state of motion and rarely stick together; shape and volume change.

Pure Substances 2-2

Pure Substances Pure substance: matter with a uniform and definite composition; contains 1 kind of matter Cannot be separated physically Ex: gold (Au), sugar/sucrose (C12H22O11), water (H2O), carbon dioxide (CO2)

Types of Pure Substances Compound 2 or more elements combined Can be broken down into simpler substances chemically Ex: salt (NaCl), baking soda (NaHCO3), sugar(C6H12O6), caffeine, water (H2O) Element Simplest form of matter Cannot be broken down any further by chemical or physical means!! Represented on periodic table of elements Ex: oxygen (O2), pure gold (Au), iron (Fe)

Symbols and Formulas Chemical Symbol: each element is represented by one- or two- letter’s. First letter is always capitalized.

Chemical Formula: shows which elements are in a compound and how many of each. Numbers in subscript show the # of atoms of each element Ex: sugar C6H12O6 water H2O carbon dioxide CO2 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms

Mixtures 2-3

Mixture Mixture Made up of 2 more substances Can be physically separated Ex: salt water, lemonade, chocolate milk, dinner salad, blood

Classifying Mixtures Homogenous: Heterogeneous: Same throughout, completely dissolved Called a solution Ex: Sugar water, air, steel, tableware (sterling silver), salt water Heterogeneous: Different compositions within the mixture Ex: orange juice, granite rock, blood

Separating Mixtures Mixtures are separated through physical means. Magnetism to separate metal filaments Filtration to separate solid from liquid Distillation = liquid is boiled separating vapor from liquid or solid substance

DRAW!

Physical + Chemical Changes 2-4

Physical Property Physical Property: quality or condition of a substance that can be observed or measured without changing the substance’s composition Includes color, solubility, odor, hardness, density, melting point, boiling point Ex: water is clear, has no odor, density is 1g/ml, boils at 100°C

Physical Changes Physical Change: is a change of matter from one form to another without changing its identity. Includes dissolving (mixing), crushing, melting, freezing, evaporating, bending, cutting It is reversible!!! Ex: Breaking a piece of chalk into two, getting your hair cut, melting ice, crushing aluminum can, mixing oil and vinegar

Physical Changes

Chemical Changes Chemical reactions occur when substances undergo chemical changes to form new substances They are irreversible! Signs of a chemical change: Gas produced (bubbling) Odor produced (gas) Color change Rusting Burning Precipitate (solid) formed Reactivity (one chemical reacts with another) Energy (light, heat, cold) released or produced

Chemical Equation 4H2 + O2  2H2O  means “yields” Reactants = substance starting a reaction, on left side of arrow A + B  C Iron + sulfur  iron sulfide Products = substance formed in a reaction, on the right side of the arrow

Conservation of Mass Law of Conservation of Mass = matter is neither created nor destroyed… Thus, mass of reactants = mass of products Atoms in a chemical reaction don’t change, they rearrange! The same number of each kind of atom must be on the left side as well as the right! Ex: H2CO3(aq) H2O(l) + CO2(g) H = 2, C =1, O = 3 H = 2, C =1, O =3