Chemistry Unit 1

substances

• contains only one element or compound

• pure

• definite composition

• homogenous

mixture of substances

• contains two or more elements and/or compounds

• physically associated

• impure

• variable composition

element

• the stuff on the periodic table!

• made of only 1 type of atom

• smallest form: atom

• CANNOT be decomposed or broken down

monatomic

made of only 1 atom

diatomic

made of 2 atoms

compound

• 2 or more different elements chemically combined

• elements take on new properties in the compound

• smallest form is the molecule

• can be decomposed or broken down into its elements

• COMBINE IN FIXED RATIOS

homogenous

• the same throughout

• a solution is an homogenous mixture

heterogenous

• different throughout

• has distinct phases & contains regions with different properties

filtration

• separates large particles by using a membrane

• usually used for mixtures of solids & liquids

• does not separate out dissolved particles (ions)

vacuum

pulls the mixture through a funnel by suction

chromatography

separate dyes & pigment by solubility and molecular polarity using filter paper

distillation

• used to separate a mixture of liquids based on their boiling points

• must have different boiling points

physical property

• a quality or condition of a substance that can be observed or measured without changing the substance’s composition

physical change

• a change that does NOT alter the chemical composition of the material

• you can get the original substance back

chemical change

• results in a change in chemical composition of the substances involved

• CANNOT get the original back (a NEW substance is formed)

mass SI unit

kilogram (kg) or grams (g)

length SI unit

meter (m)

time SI unit

seconds (sec)

temperature SI unit

Kelvins (K) or Celsius (C) or Fahrenheit (F)

electric current SI unit

amperes (A)

amount of a substance SI unit

mole (mol)

pressure

kilopascals (kPs) or atmospheres (atm)

energy

joules (J) or calories (cal)

accuracy

how close a number is to the accepted on true value

precision

how close a set of numbers are to each other (repeatability)

percent error formula

% Error = (measured value - accepted value) / (accepted value) * 100

uncertainty

always measure one place past the graduated mark

sig fig rules

• all digits other than 0 are always significant

• 0 between digits other than 0 are significant

• zero to the right of the decimal are significant if they are after a number other than 0

• 0 to the right of the whole number aren’t significant

• 0 to the left of a number aren’t significant

multiplication w/ sig figs

your answer will have the same amount of significant figures as the number w/ the least amount of significant figures in the problem

addition/subtraction w/ sig figs

your answer will have the same number of decimal places as the least in the problem

thermometry

• temperature is a measure of the AVERAGE KINETIC ENERGY of the particle in a system

• heat flows SPONTANEOUSLY from a system at higher temperatures to a system of lower temperatures