Matter, Density, Relative Density

Obj 1: 3 common states of matter

(Plasma is another state but not part of this module)

Solids terms:

Liquids terms

Gas Terms

compressible: may be compressed
Diffusion: 2 or more gases mixing rapidly and effortlessly into a uniform mixture (ex: natural gas smelt into a room)
Fluidity: gases flowing with air movement due to their density (ex: heavy H2S flowing to lower areas)

state of matter depends on pressure and temperature. (Melting, vaporized, frozen, condensation)
Physical change does not affect chemical composition (ex: water boiling, water freezing)
Chemical change produces a new substance either different chemical compositions (ex: burning a fuel)

obj 2 - matter, element, compound, mixture terms

Molecular Theory

Molecule: substance reduced to the smallest particle. Made up of atoms. Some may have one atom, some may have multiple.
- molecular theory helps explain:
  - heat energy
  - Electrical energy
  - Why changes of state occur
  - Categorizing and classifying other substances.
Atom:
- smallest form of matter
- Composed of protons(positive charge), neutrons(no charge), electrons(negative charge)
- Nucleus contains protons and neutrons. Electrons orbit the nucleus
- In any atom, # protons is equal to # electrons and is electrically neutral
Element:
- composed of only one kind of atom, substance cannot be reduced any further. Ex: O2 or Hydrogen
- There are only about 100 different atoms but thousands molecules- atoms or elements are divided into 2 categories:
  - metals: generally good conductors of heat and electricity
  - Non metals: not good conductors of heat and electricity (carbon, silicon, hydrogen, oxygen)
Compounds
- made up of molecules or atoms and chemically joined. (Original molecule properties are lost)
- Can be broken down
- If composed of only one kind of molecule it is a pure substance
- Ex: H2O, CH4.
Mixtures:
- combination of different molecules and is not chemically combined(each molecule retains its properties)
- Ex: Solder, brass, air, any alloys.
Solutions:
- one substance is dissolved by another.
- If the mixture is the same throughout it is homogeneous
- Solute: what is being dissolved
- Solvent: what does the dissolving

obj 3- adhesion, cohesion, surface tension, capillarity

Adhesion
- attraction of different molecules to eachother
- Ex: water drawing up the side of a vessel (the upward or downward curve is called the meniscus- for water this meniscus is concave), glue adhesion
Cohesion
- Opposite of adhesion; attraction between the same molecules
- Ex: mercury not wetting a vessel surface- it merely depresses in the mercury and makes an convex meniscus
Surface Tension
- skin or meniscus of a liquid is created by surface tension. (The molecules on liquid have greater attraction to themselves rather than the air above) - think of a glass of water slightly overfilling and not spilling
Capillarity (capillary action)
- Ability of liquid to rise or drop in small tubes inserted in the liquid.
- Both adhesion and cohesion produces this
  - if adhesive force > cohesive, liquid rises in the tube until mass of liquid is equal to pressure exerted by surface tension.
  - Smaller or tighter opening: more rising or falling action based on adhesion/cohesion relationship. Which is better capillary action
  - Larger tube or clearance = worse capillary action. This is why soldering is so effective, the gap is very tight.

Calculate mass, density, volume of substances

Density: mass per unit volume (usually m3, ft3, in3), ex: 1000kg/m3
- Mass = Density x volume
- Density = Mass / volume
- Volume = mass / density

Substances expand when heated; volume expands and density decreases
- only exception is water between 0 and 4C; it actually becomes more dense when it is heated from 0 to 4C, but then it begins to decrease in density from there.
- If water freezes, it also expands about 7.5% as it changes to ice. Lakes freeze top down since the top is the coldest. Water at 4C is more dense and is at the bottom of the lake, water at 0C is less dense and at the top of the lake.
Specific Gravity (Relative Density)
- number of times a substance is heavier or lighter than an equal volume of either Air (if its gas) or Water (if its liquid or solid)
- Unitless because the units cancel out
- Ex: steel is 491 lb/ft3 is SG of 7.87;
  - 491 / density of water in lb/ft3 which is 62.4= 7.87 without any units.
  - Same applies for gas but using density of air which is 0.076 lbs/ft3
  - If you have specific gravity of something and want to convert to density you multiply it by either the water or air density (depending on what state the material is in):
    - mercury= 13.6 × 62.4 lbs/ft3= 848.64 lb/ft3
OTHER:
Water expands about 7.5% when freezing.
Water is most dense at 4 Deg C.
Units:

Density of Water:

Density of Air:

Imperial: 0.076 lbs/ft3
Metric: 1.29 kg/m3
You cannot just memorize the imperial and convert the lbs to kg. It is a different calculation.
Specific gravity and relative density are the same thing

Weight of Water:

Density of Mercury:

SG of gases:

SG of Liquids/Solids: