Chemical Substances and Mixtures - UNIT 1

Element

A pure substance made of only one kind of atom

Compound

A substance made of different types of atoms chemically bonded

Mixture

A combination of two or more substances that are not chemically bonded

Homogeneous

Uniform composition no matter what part you chose to observe, like saltwater or sugar & water

Heterogeneous

Non-uniform composition, like a salad

What is the difference between homogenous and compounds?

Not chemically bonded

Atom

Smallest sample of matter, one atom & it isn't chemically bonded

Are atoms bigger than molecules?

NO

Molecule (of an element)

A group of atoms bonded together, at least two atoms chemically bonded together

Chemical Bond

A force that holds atoms together in a compound

Classification of matter

Matter is split up into two sections:
PURE SUBSTANCE & MIXTURES

Pure Substances: either elements & compounds
Mixtures: Homogenous & heterogenous

Pure substance

A substance made of only one kind of matter and having definite properties.
Ex. Water & gold

Pure substance are either element & compound
Elements: whose atoms all have the same number of protons Ex. H2, Cu ---> elements are then atoms or molecules

Compound: formed when two or more chemical elements are chemically bonded together. Ex. H2O, NaCl

Mixture

Heterogeneous & homogenous

Heterogeneous mixture: one in which the composition varies from one region of the mixture to another.
Example: a salad

Homogeneous mixture is one made of multiple substances but appears to be one substance. UNIFORM. The atoms or molecules that compose them mix uniformly.
Example: a salt and water mix or sugar & water

Molecular Elements (Diatomic Molecules)

Elements that have 2 atoms of the same type being chemically bonded
- H2, O2, N2, F2, Cl2, Br2, I2 (7 on periodic table)

2 polyatomic elements

P4, S8

Physical change key words

Boil, melt, freeze, crush, cut, dissolve, condense, bend

Chemical change key words

rust, oxidize, corrode, tarnish, ferment, burn, rot

Physical changes

stays as same substances but goes through different states of matter
ex. ice (solid w/ strong IMF) -> (liquid w/ weak IMF) -> (gas w/ no IMF) (melting to evaporation)

Chemical changes

4 H2 & 2 O2 -> electrolysis w/ electric current -> creates H2O

Units of measurement

Metric: used in most of the world
English system: United States
SI units: based on metric system

MUST KNOW CONVERSIONS

1 m = 100 cm
1 cm = 10 mm
2.54 cm = 1 inch

Metric system

Length: m
Mass: g
Volume: L
Temperature: Celcius
Time: seconds

Length:

km -> m
m -> cm
cm -> mm
mm -> nm

Mass

kg -> g
g -> mg
mg -> mcg

Volume

L -> mL
L -> dL
L -> cL

Temperature

Celsius -> Kelvin (K)
Celsius + 273.15 = K