HSC Chemistry
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Module 1: Properties and Structure of Matter1.1 Properties of Matter
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1.2 Atomic Structure and Atomic Mass
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1.3 Periodicity
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1.4 Bonding
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Module 2: Introduction to Quantitative Chemistry2.1 Chemical Reactions and Stoichiometry
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2.2 Mole Concept
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2.3 Concentration and Molarity
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2.4 Gas Laws
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Module 3: Reactive Chemistry3.1 Chemical Reactions
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3.2 Predicting Reactions of Metals
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3.3 Rates of Reactions
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Module 4: Drivers of Reactions4.1 Energy Changes in Chemical Reactions
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4.2 Enthalpy and Hess's Law
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4.3 Entropy and Gibbs Free Energy
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Module 5: Equilibrium and Acid Reactions5.1 Static and Dynamic Equilibrium5 Topics
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5.2 Factors that Affect Equilibrium2 Topics
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5.3 Calculating the Equilibrium Constant2 Topics
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5.4 Solution Equilibria
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Module 6: Acid/Base Reactions6.1 Properties of Acids and Bases7 Topics
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6.2 Using Brønsted–Lowry Theory2 Topics
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6.3 Quantitative Analysis1 Topic
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Module 7: Organic Chemistry7.1 Nomenclature2 Topics
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7.2 Hydrocarbons2 Topics
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7.3 Products of Reactions Involving Hydrocarbons
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7.4 Alcohols1 Topic
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7.5 Reactions of Organic Acids and Bases
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7.6 Polymers2 Topics
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Module 8: Applying Chemical Ideas8.1 Analysis of Inorganic Substances3 Topics
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8.2 Analysis of Organic Substances
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8.3 Chemical Synthesis and Design
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Working ScientificallyWorking Scientifically Overview1 Topic
Non-Equilibrium Systems
Combustion
When hydrocarbons undergo complete combustion in an excess of oxygen, carbon dioxide and water are formed. These reactions are strongly exothermic:
\text{CH}_4 (g) + 2\text O_2 (g) \rightarrow \text{CO}_2 (g) + 2\text H_2 \text O (l)
The release of heat energy in this exothermic reaction drives the reaction in the forward direction. This reaction is spontaneous as the Gibbs free energy change is negative. (ΔG < 0).
The high activation energy for the reverse reaction reduces the chance that products will recombine to form reactants. Also, as combustion reactions occur in open systems, the products can escape into the surroundings and therefore cannot recombine to produce reactant molecules.
Photosynthesis
Photosynthesis occurs in the chloroplasts of green plant cells. Solar energy is absorbed by chlorophyll molecules inside the chloroplasts.
Chlorophyll selectively absorbs red and violet light in the visible spectrum. This energy is used to convert carbon dioxide and water into glucose and oxygen, as seen below:
6\text{CO}_2 (g) + 6\text H_2 \text O (l) \rightarrow \text C_6 \text H_{12} \text O_6 (s) + 6 \text O_2 (g)
The Gibbs free energy change for photosynthesis is positive (ΔG > 0) and therefore the reaction is non-spontaneous. This reaction requires solar energy to occur.
The reaction products are lost from the system and this prevents the reverse reaction from ocurring.