Chemistry Unit Notes

Topic 1: Exploring Matter

♦ Know your WHMIS safety symbols

♦ Particle Theory 1. Matter is made up of very small particles2. Pure substances have their own kind of particle.3. Particles attract each other4. Particles always move5. If you increase temperature the particles move faster

♦ Classifying Matter:Pure Substances: - made up of one kind of particle

- can include: Elements, molecules and compound molecules

Mixtures: -made up of more than particle-solutions: look like they have only one kind of particle (homogeneous)- mechanical mixtures: can see more than one kind of particle (homogeneous)

- suspensions: large particles that settle to the bottom of the container- colloids: smaller particles than suspensions, colloids in liquids are called emulsions.

Topic 2: Changes in Matter

♦ Physical change: a change that doesn’t create a new kind of particle (chemical). They are often easy to reverse. Ex. Cutting, melting, boiling, dissolving etc.

♦ Chemical Change: a change that does create a new kind of particle (chemical). Indicators of chemical change

1. heat is produced or absorbed2. starting material is used up3. change in colour4. A material with new properties is formed5. Gas bubbles form in a liquid6. A precipitate (solid) forms from mixing two liquids7. The change is difficult to reverse

Physical properties: Properties that can be measured without a chemical change. Ex. Density, Melting pointChemical properties: Properties that can only be observed by having a chemical reaction. Ex. Combustibility

Topic 3: What are Elements

♦ Elements are the groups of pure substances that can’t be broken down further (without nuclear reactions).

♦ Elements are made out of atoms. Atoms are the smallest, simplest particles of a pure substance. Atoms can be rearranged to make compounds and molecules.

♦ All chemical changes are governed by two Laws.1. The Law of conservation of Mass: in a chemical change the mass of the reactants

always equals the mass of the products.2. The Law of Definite composition: compounds are pure substances that contain

two or more elements combined in definite proportions.

So for the equation:

Reactants → Products

CH4 + O2 → H2O + CO2

16g 64g 36g 44g

***** Note that in the above example reactants are on the left side of the arrow, products are on the right side of the arrow. The mass of the reactants equals 80g and the mass of the products equals 80g (Law of conservation of mass). You should also notice that in CH4 there is one Carbon atom, and four hydrogen atoms (Law of definite proportions).

Electrolysis Reactions:

♦ Carried out in a Hoffman’s apparatus (shown to the right), it splits water compounds into oxygen molecules and hydrogen molecules

Water → Oxygen + Hydrogen

H2O → O2 +H2

♦ The electrolysis reaction proves that compounds are made of more than one kind of element.

Dalton’s Atomic Theory:1. All matter is made up of small particles called atoms2. Atoms can’t be created or destroyed.3. Atoms of the same element have the same size and mass, but are different from other element’s

atoms.4. Compounds are created when atoms of different elements link together (bonding- either ionic

or molecular).

**** Dalton thought atoms were small complete single particles (like little balls)

History of Atomic Models:

Thompson: Plum pudding model. Electrons and protons are mixed throughout the atom.

Rutherford’s Planetary model: Electrons go around the nucleus (made of neutrons and protons) like little planets around the sun.

Bohr Model: Electrons have orbits around the nucleus and have fixed paths.

Electron Cloud model: Electrons are found in clouds that surround the nucleus.

Topic 4: Classifying Elements

♦ All elements are represented by a capital letter (H for hydrogen) or a capital letter and a lower case letter (He for helium).

Kind of Elements:There are a 3 kinds of elements:

I. Metals: are found on the left side of the periodic table, are ductile (can be stretched into wire), malleable (can be pounded into different shapes). They are also good conductors of both heat and electricity. Metals are shiny and are solid (except mercury).

II. Metalloids: are found along the staircase in the periodic table. They are not ductile, they are brittle, they may conduct electricity, but are poor conductors of heat. Metalloids can be shiny or dull, they are solid.

III. Non-Metals: are found to the right side of the periodic table. They are not ductile, are brittle, don’t conduct heat or electricity well. They can be liquid, solid or gas.

Chemical Families: There are four main chemical families. They are found in the columns (up and

down) on the periodic table. The four chemical families are:I. Alkali metals: found in column one (left column). They have an

unpaired electron, so they are very reactive. (electrons like to be in pairs).

II. Alkali Earth Metals: found in the second column. They are less reactive than the alkali metals, but are pretty reactive.

III. Halogens: found in the seventh column, they are very reactive because they have an unpaired electron. They react violently with Alkali metals.

IV. Noble gases: are in the eighth column (right column). They are not reactive (they don’t have any unpaired electrons), and are gases. Noble gases are used in lights (eg. Neon lights).

Topic 5: The Periodic Table

♦Mendeleev created the periodic table. He created by comparing the properties of different known elements.

♦ The properties uses were reactivity (what reacts with what), density, melting point, boiling point.

♦ The columns have similar reactivity.

♦ Elements are ordered so they are in increasing atomic mass.

♦Mendeleev was able to predict undiscovered elements because of his table.

Atomic Mass and Atomic Number:

The modern periodic table is organized by increasing atomic number.The atomic number = # protonsThe atomic mass = # protons + # neutronsThe overall charge of the atom is determined by the number of electrons compared to the number of protons.

→ Flourine Mass number =19 → 19 heavy particles (protons and neutrons) Atomic number = 9 → 9 (protons, which are positively

charged)

If the fluorine has a charge of 0 (neutral charge) then there are 9 electrons******If fluorine has a charge of -1, then there are 10 electrons (one more negative charge than positive charge)

Element Name Chemical Atomic Atomic # of #Neutrons #Electrons

19 F9

Symbol Number Mass ProtonsMercury Hg 80 200.59 80 121 80Chlorine Cl- 17 35 17 18 18

*** note, when the atom is charged the number of electrons changes, when uncharged the number of electrons = protons

Topic 6: Chemical Compounds

There are 4 types of compounds you should know:

Type of Compound

Description Example

Diatomic -Has only got two of the same atom O2, H2, N2

Binary -Has only two types of elements NO, H2O, CO2, NaClMolecular -Shares electrons between atoms

-Does not contain metalsNO, H2O, CO2

Ionic -Atoms have either positive or negative charges.-Atoms held together (opposites attract)-Contains a metal and a non-metal or metalloid-Conducts electricity pretty well (in solution).

NaCl, MgCl2, Na2O

Naming Chemical Compounds:

Ionic Compounds: 1. Write the metal name2. Write the name of the non-metal/metalloid, with “ide” at the end.

Ex. NaCl → sodium chloride MgCl2→ magnesium chloride

Molecular Compounds:1. Write the name of the first element2. Change the name of the second element to “ide”3. Use a prefix for the last element [mono (1), di (2), tri (3), tetra (4)] and use a

prefix for the first element *** but don’t if there is only one [di (2), tri (3), tetra (4)]

Ex. CO2 → Carbon DioxideEx. H2O → Dihydrogen monoxideEx. H2O2 → Dihydrogen dioxide

Topic 7 &8Energy in Chemical Reactions

i) Energy: 2 categoriesKinetic

(movement of particles)Potential

(stored energy)sound gravitationalelectrical (current) chemicalmechanical elasticlight electrical (static)

ii) Exothermic Reactions

● release energy (usually heat)

● e.g. combustionCu(II)SO4 + steel wool → heat + other products

iii) Endothermic Reactions

● absorb energy (usually heat)

● e.g. baking muffins

Controlling Chemical ReactionsReaction rates can be controlled with:iv) Surface Area

● As surface area increases, rate of reaction will increase

● As surface area decreases, rate of reaction will decrease

● (painting, galvanizing etc)

v) Concentration

● As concentration increases, rate of reaction will increase

● As concentration decreases, rate of reaction will decrease

vi) Temperature

● As temperature increases, rate of reaction will increase

● As temperaturedecreases, rate of reaction will decreasev) Inhibitors

♦ Chemicals that slow down reactionsvi) Catalysts

♦ Chemicals that Speed up reactions

Corrosion

● chemical reactions that use up metals are corrosion reactions

● metals are 'eaten away' (corroded)

● e.g. rusting of iron

vii)Preventing corrosion

● reduce surface area by painting, covering etc.

● reduce temperature by storing in cold place, in the shade, etc.

● reduce concentration by storing away from high humidity or corrosive fumes

Law of Conservation of Mass:In a chemical reaction the mass of the products always equals the mass of the reactants, because atoms aren’t made or destroyed. They are just rearranged.

Mass of reactants = Mass of Products.

Balancing Chemical Equations:There is an equal number of each kind of atom in the reactants as there are in the products.

*****(this comes from the law of conservation of mass, since there is equal mass or reactants and products, the number of each atom in the reactants and products must be equal).

1C2H4 + 3O2 → 2CO2 + 2H2O

C= 2x2 = 4 O= 6x2 = 12 C= 4x1 = 4 H= 4x2 = 8H= 2x4 = 8 O= 4x2 = 8 0= 4x1 = 4