Nature of Science
"is the search for the truth“

First Nations perspectives
• Medicine Wheel
• Four directions
• Four Elements

Early Civilization perspectives
• Greek Elements
• Chemistry started with Democritus

Chemistry is the study of the composition and properties of matter
Chemists interested in:
1) composition and structure of substances
2) the properties of these substances
3) the conditions under which these substances change to form new ones

Forms of Matter
• Mass
• Volume
• Four States: Solid, Liquid, Gas, Plasma

Classifying Matter
• Matter has ‘property’

Pure Substances
• Elements
• Compounds

Mixtures
• Mechanical mixture
• Suspension
• Solution

Using mixtures in mining

Physical Properties
• Water is unique

Physical Properties
• Colour and lustre
• Melting point
• Boiling point
• Density
• Solubility
• Ductility
• Crystal Shape
• Conductivity
• Hardness
• Texture
• Malleability

Chemical Properties
• Change and Reaction
• Takes heat energy or light


Combustion
Controlled Change
• Traditional uses – preserving foods
• Medicines – herbs and plants

Polyethylene Plastics

Models of Matter
Remember: began with the Greeks
- Democritus
Then: Alchemists
Finally: Modern Chemistry Begins

Different Ways of Understanding
1) Greeks (Democritus) – 400 B.C.
2) Dalton – 1803
A small particle with several smaller pieces within.

3) Thompson – 1898
The Plum Pudding Model
4) Rutherford – 1911
Concentric Rings

5) Bohr – 1923

6) Scroedinger – Present
Quantum Mechanical Model
Based on the probability of where electrons would be found about the nucleus.

We are interested in three particles and their mass, charge, and location.
Mass Charge Location
Proton
Neutron
1 AMU
1 AMU
+
Electron 1/1836
AMU
AMU – Atomic Mass Unit
-
In Nucleus
Neutral In Nucleus
Outside
Nucleus


In an atom/element the number of protons is always equal to the number of electrons.

We always round the atomic mass to the nearest whole number.
# Neutrons = Atomic Mass - Atomic Number

16
Sulfur
32.06
Atomic Number – Tells us the number of protons
Element Symbol
Element Name
Atomic Mass – tells us the number of neutrons and protons

E. Ions
 ions are formed when an electron is either gained or lost.

 when an electron is gained, it becomes a negative ion and we call this an anion.
when an electron is lost, it becomes a positive ion and we call this a cation.

When naming a cation, simply add the word 'ion' to the end of the element name.
Ex//
Mg - Magnesium  Mg +2 - Magnesium ion
Ca - Calcium  Ca +2 - Calcium ion
Na - Sodium  Na +1 - Sodium ion

When naming an anion, drop the last few letters of the element name and add the ending -ide.
Ex//
O - Oxygen  O -2 – Oxide
N – Nitrogen  N -3 - Nitride
Cl - Chlorine  Cl -1 – Chloride
 ions become charged because they want 8 electrons in their outer shell (octet)

 When an anion and a cation come together, they form a compound.

Compounds are a combination of two or more elements
 when an atom loses an electron, it becomes positive which is known as a

 cation.
when an atom gains an electron, it becomes negative which is known as an anion.
Cations and anions are attracted to each other and thus come together to form a compound.

• Compounds must be balanced so that the positive charges balance the negative charges.
• Compounds must also be written in lowest possible form.

NAMING
 the cation always goes first, followed by the anion.

 use the element name for the cation.
use the ion name for the anion.
1. a) Li +1 b) Mg +2 c) Ca +2 d) Cu +2 e) Cr +3 f) Fe +2 g) Ag +1 h) Al +3 i) Fe +3
P
O
-3
F -1
N -3
O -2
S -2
S -2
S -2
Br -1
-2

K
Ca +2
Cr
+1
+3
Cl -1 O -2 N -3
KCl
Potassium
Chloride
K
2
O
Potassium
Oxide
K
3
N
Potassium
Nitride
CaCl
2
Calcium
Chloride
CrCl
3
Chromium
(III)
Chloride
CaO
Calcium
Oxide
Cr
2
O
3
Chromium
(III)
Oxide
Ca
3
N
2
Calcium
Nitride
CrN
Chromium
(III)
Nitride

2. Write the chemical formula for each of the following compounds.
a) Potassium chloride b) Calcium nitride c) Copper (II) oxide d) Iron (III) bromide e) Magnesium phosphide f) Aluminum selenide g) Chromium (III) sulfide h) Tin (II) oxide

3. Name each of the following compounds.
a) Li
2
O b) Ag
3
N c) SnO
2 d) CrCl
3 e) BaS f) Fe
2
O
3 g) Cu
3
P h) V
2
O
5

Products
- are the chemicals that are made or produced in a chemical reaction
Reactants
- are the chemicals that begin or go into the reaction before it takes place

Chemical Reaction
- when the chemicals that go into the reaction change and new products
(chemicals) are formed.
Ex.
MgI
2
+
Reactants
Na
2
O  NaI +
Products
MgO
When we write the compounds, we must make sure that they are balanced.

‘+’ – tells us that two compounds are combining.
Key Words – combines, mixes, reacts, and, etc.
‘  ’ – acts as an equals sign to separate reactants and products.
Key Words – to form, to produce, to make, synthesize, decompose, break down, etc.

1) Magnesium bromide reacts with calcium nitride to form magnesium nitride and calcium bromide.
2) Copper (II) oxide reacts with lithium phosphide and produces copper (II) phosphide and lithium oxide.

3) Tin (IV) sulfide reacts with calcium iodide and makes tin (IV) iodide and calcium sulfide.
4) Lithium chloride decomposed to form lithium and chlorine.
Magic Seven – if ever the following elements are by themselves, they are found in pairs (diatomic).
N
2
, O
2
, F
2
, Cl
2
, Br
2
, I
2
, At
2
, H
2

5) Calcium reacts with iodine to form calcium iodide.
6) Chromium (III) iodide combines with sodium phosphide to make chromium (III) phosphide and sodium iodide.

Examples
1) CaI
2
+ Al
2
O
3
 CaO + AlI
3

2) CrI
2
+ Cu
2
S  CrS + CuI
3) Fe
2
O
3
+ KF  FeF
3
+ K
2
O

Acids

Have a sour taste


Very corrosive
Neutralize bases



Conduct electricity very well
Dissolve in water to produce hydrogen ions (H + ) in solution
When an acid and a base neutralize each other, they form salt and water
NaOH + HCl
Sodium

Hydrochloric
H
2
O + NaCl
Water Salt
Hydroxide Acid

Bases


Have a bitter taste
Very corrosive




Neutralize acids
Conduct electricity very well
Dissolve in water to produce hydroxide ions (OH ) in solution
When an acid and a base neutralize each other, they form salt and water

Acid-Base Indicators
• Acid – Base indicators are substances that change different colors when added to acids and bases.
• Litmus Paper – red in an acid
- blue in a base
• Bromothymol Blue – yellow in an acid
- blue in a base

pH paper – is another type of indicator that can change to several different colours to tell the scientist how acidic or basic the solution is.

pH Scale






An acid-base indicator will not tell you how acidic or basic a solution is.
The pH scale indicates the level of acidity of a solution and it ranges from 0-14.
pH of 0-6.9 is acidic.
pH of 7 is neutral.
pH of 7.1-14 is basic.
The pH scale is logarithmic (based on the power of ten). This means the difference between a pH of 5 and 6 is actually ten times. The difference between 4 and 6 is actually 100 times.

Maintaining a constant pH is often very important for biological systems.



Human blood has a pH range of 7.35-
7.45. Any change from this could be fatal.
Plants grow best in soil with a pH between
6 and 7. Any higher or lower, prevents the plants from absorbing nutrients.
Shampoo normally has a pH of about 8.
The human scalp has a pH of about 6. A scalp that becomes too basic results in dandruff.

Exam Time!