Pure SubstancesElements

Composed of one type of atomMetal, Non-metal or MetalloidSimplest type of matter that retains characteristic properties

Pure SubstancesCompounds

A combination of two or more elements

Properties differ from those of component elements

Separated by chemical means

MixturesHeterogeneous

Has one or more visible boundaries between the components

Composition is not uniformSome boundaries may only be seen with a microscope ie. Blood, milk

MixturesHomogeneous

No visible boundaries because components are mixed as individual atoms, ions or molecules

Composition is uniform on a molecular level

Alloy- steel, a combination of Fe and CWe cannot tell visually whether an object

is a substance or a homogenous mixture

FiltrationSeparates the components of a

mixture on the basis of differences in particle size

Usually a heterogeneous mixtureMost common method is to use filter

paper to separate the components. The remaining liquid, after separation, is the filtrate.

Separation techniquesFiltration – uses a porous barrier to separate

a (non-dissolved) solid from a liquid

DistillationSeparates components through differences in

volatility : used for homogenous mixtures

The mixture is heated until the substance with the lowest boiling point becomes a vapor that can be condensed into a liquid and collected.

If the distillation is controlled ,you can separate substances that differ by a few degrees.

Distillation – separates liquids based on their boiling points

CrystallizationBased on differences in solubilityWhen a solution contains as much

dissolved substance as it can possibly hold it has reached the saturation point

The addition of even a tiny amount causes the dissolved substance to come out and collect as crystals

Crystallization – a method of extracting dissolved solids from a solution

ChromatographyBased on differences in solubilityThe separation is based on the

various components of the mixture spreading out through the paper at different rates

Components with the strongest attraction for the paper move slower (highly soluble)

Chromatography – separates components of a mixture based on how well it can travel across a particular material

Law of Conservation of Mass

Mass is neither created nor destroyed it just changes form:

Mass reactants = Mass products

A 10.0 g sample of magnesium reacts with oxygen to form 16.6 g of magnesium oxide. How many grams of oxygen reacted?

What part of the reaction is a compound?

From a laboratory process designed to separate water into hydrogen and oxygen gas, a student collected 10.0 g of hydrogen and 79.4 g of oxygen. How much water was originally involved in the process?

If 19.9 grams of copper are burned in air to produce 25.0 grams of copper oxide, what is the mass of oxygen from the air that is needed?

Law of Conservation of MassApplies to compounds:

The mass of a compound is equal to the sum of the masses of the elements that make up that compound

20.00 g of sugarCarbon 8.44

Hydrogen 1.30

Oxygen 10.26

sum 20.00

Find Percent by Mass of each element:

Law of Definite Proportions

percent by mass = mass of element x 100

mass of compound

Carbon: 8.44 g C X 100 = 42.20 %

20.00 g sucrose

Hydrogen: 1.30 g H X 100 = 6.50 %

20.00 g sucrose

Oxygen:

Analyze 500.0 g sucrose

Carbon 211.0Hydrogen 32.5Oxygen 256.5

sum 500.0

A 78.0 g sample of an unknown compound contains 12.4 g of hydrogen. What is the percent by mass of hydrogen in the compound?

What is the percentage by mass of I if 4.07 g reacts with 10.63 g of II to form a compound of mass 14.70 g? Also, calculate the percentage by mass of II in the compound.