Columbia College
Chem 100 (Winter 2023)
Week 2: In-class Notes and Summary
CHEM 100 - Introduction of Chemistry – Week 2
1. Molecules
a. Smallest unit in many pure substance (elements or compounds)
b. Group of two or have tightly bound atoms in a specific whole number ratio
i. Diatomic molecules (two atoms)
ii. E.g., oxygen gas (O2)
c. Polyatomic molecules (two or more atoms)
i. E.g., pure water (H2O)
2. Properties of matter
a. dictated by its composition
b. can be classified as either phycical properities chemical properties
c. behaviour matter = properties and composition
3. Molecular Formula
a. The elemental composition of molecules
b. Symbol for each atom following by numerical subescript to indictate the muner of thst
type of atom present in one molecular
i. H2SO4 <If not subscript shown implied value = 1>
4. Physical properties
a. characteristics of a substance that can be determined without changing the chemical
composition of that substance
i. Shape changes but atoms are not arranged
ii. Reversable
iii. colour
iv. odor (smell)
v.
melting points
vi. Boling points
vii. Density (substance which the ratio of mass over volume)
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Columbia College
Chem 100 (Winter 2023)
Week 2: In-class Notes and Summary
5. Chemical properties
a. the ability of a substance to react and to change into other substances
i. heat of combustion (the amount of heat released during combustion)
ii. reactivity with water
iii. PH
iv. Flammability (the capability of a substance to burn/ignite/combust/catch fire)
6. Pysical change
a. a substance changes in physical properties or changes in state
i.
Sublimation: CO2 dry ice ->>gaes
Deposition: gaes ->> CO2 dry ice
7. Chemical change
a. the chemical composition (identity) of a pure substance is altered as a result of a
rearrangement of atoms
b. Reactants: the substance which are present before the change occurs
c. Products: the substances which are present after the change occurs
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Columbia College
Chem 100 (Winter 2023)
Week 2: In-class Notes and Summary
8. Chemical reaction
a. differcult to indentify tham phycial change
b. look for obsevrable signs
i. colur change
ii. odor change
iii. evolution of a gas ( bubbling, fizzing)
iv. formation of preipitate (heterogeous mixture)
v. light production (heat generation)
vi. smoke and frame
vii. presence of heat/ cool (homogeous mixture)
viii. not reversable
ix. Fermentation (wine)
1. meat/ milk got bad -> changing smell/ odor/ taste
2. burning wood -> production of heat
3. tarnishing of sliver
4. corrosion (rusting) of iron
9. Chemical equations
a. Shortened for expressing the chemival change which lists the formaula of the reaxtants,
followig by an arrows -> products
b. Balance the equation
i. the number of atoms of each types must equal to product atoms
1. 3H2(g) + N2(g) -> 2NH3(g)
10. Stoichiometric coefficients
a. Numbers placed in front of chemical formula
b. Equations to balance
c. Expressed in whole number and lowest terms
d. If there is no number = 1
e. Applying to an atom in the formula
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Columbia College
Chem 100 (Winter 2023)
Week 2: In-class Notes and Summary
11. State of matter
a. Solid (s)
b. Liquid (l)
c. Gas (g)
d. Aqueous solution - disolving in the water (aq)
12. Endothermic reactions
a. Consume and assorb heat
b. Heat + reactants -> products
c. (Heat +) CuO (s) + HNO3 (aq) -> Cu(NO3)2 +H2O (l)
i. Heat +Black powder + colurless liquid = blue liquid (aq)
d. Ice melting in phyical change
i. (Heat +) ice -> ( vapourization) water
ii. Ice ssorbed heat and the bond is broken by the heat energy
13. Exothermic reactions
a. Give off, release, and produce heat
b. Reactants -> products heat
i. Combustion reaction in chemical change
1. Highly exothermic reaction
2. Substance reacts with oxygen
3. Usually producing flame and light + water vapour
4. Temperture goes up
a. C3H8(g) +5O2(g) -> 4H2O(g) + 3CO2(g) (+heat)
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