QUICK REVIEW

Melting Wax / Burning a Candle
Physical Change / Chemical Change
Change of state
  • Solid to liquid
/ Chemical reaction
  • Reactants: wax + oxygen (from air)
  • Products: carbon dioxide + water vapor

Can be reversed
  • If we cool wax it goes back to solid form
/ Cannot be reversed
  • Heat and light produced
  • Wax has “disappeared”

Law of Definite Proportions
Used to determine if two compounds (with same elements) are indeed the same.
ALL elements have to have the SAME % Mass in the compound to be the same substance.
Law of Multiple Proportions
Used to compare two DIFFERENT compounds that are made up of the EXACT same elements, but different amounts.
Example:
Compound / % mass O / % mass C / Mass Oxygen (100g sample) / Mass Carbon
(100g sample) / g O/ g C
Compound A / 57.1 % / 42.9 % / 57.1 g / 42.9 g / 1.33 g O/ g C
Compound B / 72.7 % / 27.3 % / 72.7 g / 27.3 g / 2.66 g O/ g C
Find the Whole Number RATIO (Law of Multiple Proportions)
  • Dividing the mass of O per g C of the second (larger) compound
  • 2.66/1.33 = 2
  • Our ratio is 2:1 or

Separating Mixtures
Distillation / Separates mixture based on the boiling points of the individual substances involved / Example: separating two liquids

Filtration / Separates solids from fluids (liquids or gases) / Example: separate unwanted particles from drinking water

Crystallization / Separates mixture by the formation of solid crystals precipitating from a solution / Example: Rock Candy Lab, separate sugar from water

Chromatography / The mixture is dissolved in a fluid called the mobile phase, which carries it through a structure holding another material called the stationary phase. The various constituents of the mixture travel at different speeds, causing them to separate / Example: Separating inks

States of Matter
Solid / Liquid / Gas
Particles very close together / Particles a little farther apart / Particles very far apart
Not much room to move / Some room to move / Lots of room to move
Has a distinct shape / Takes the shape of container / Fills the shape of container
Milk
Heterogeneous Mixture USE THIS FACT FOR ANY TESTING PURPOSES
WHY???
  • Fresh milk separates spontaneously into cream, which floats to the surface with watery below.
  • Homogenized milk is made by breaking the cream into tiny droplets and mixing them into the rest of the milk. This prevents the cream from separating.
  • Macroscopically, it is homogeneous, that's why it is called homogenized. HOWEVER‼‼‼‼ Microscopically, it is still heterogeneous, since the fat is not actually dissolved into the water

Milk is a colloid.
  • A colloid is a heterogeneous mixture in which the particles do not settle out, like oil settles from water.
  • Another example of a colloid is blood. Blood is made up of plasma, cells, and other substances, although it appears as one solution.
  • Milk is also made up of separate substances.
  • 'Homogenized' milk is milk in which fat globules have been broken down into very fine particles. It's not homogeneous, but steps have been taken to make it seem less heterogeneous.