Photosynthesis is a fundamental biological process that sustains life on Earth by converting light energy into chemical energy. For students preparing for the Cambridge IGCSE in Chemistry (0620 - Core), understanding the photosynthesis equation is crucial. This process not only highlights the intricate relationship between plants and their environment but also underscores the significance of air quality and climate within the chemistry of the environment.

Key Concepts

The Basics of Photosynthesis

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. This process occurs primarily in the chloroplasts of plant cells, where chlorophyll pigments capture sunlight. The overall chemical equation representing photosynthesis is: $$ 6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2 $$ Here, six molecules of carbon dioxide ($CO_2$) and six molecules of water ($H_2O$) react to form one molecule of glucose ($C_6H_{12}O_6$) and six molecules of oxygen ($O_2$).

Structural Components Involved

The primary structures involved in photosynthesis are chloroplasts, which house chlorophyll pigments. Chlorophyll absorbs light, primarily in the blue and red wavelengths, and converts it into chemical energy. Within chloroplasts, thylakoid membranes contain photosystems I and II that play pivotal roles in the light-dependent reactions of photosynthesis.

Light-Dependent Reactions

The light-dependent reactions occur in the thylakoid membranes and involve the absorption of light by chlorophyll. This energy is used to split water molecules ($H_2O$) into oxygen, protons, and electrons: $$ 2H_2O \rightarrow 4H^+ + 4e^- + O_2 $$ The electrons and protons generated are then used to produce adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH), which are essential for the subsequent light-independent reactions.

Calvin Cycle (Light-Independent Reactions)

The Calvin Cycle takes place in the stroma of chloroplasts and does not require light directly. Instead, it utilizes the ATP and NADPH produced during the light-dependent reactions to convert carbon dioxide ($CO_2$) into glucose ($C_6H_{12}O_6$). This cycle comprises three main phases:

Carbon Fixation: $CO_2$ molecules are attached to ribulose bisphosphate (RuBP) catalyzed by the enzyme RuBisCO.
Reduction Phase: The energy from ATP and NADPH is used to convert the fixed carbon into glyceraldehyde-3-phosphate (G3P).
Regeneration of RuBP: G3P is used to regenerate RuBP, allowing the cycle to continue.

Role of Chlorophyll

Chlorophyll is the green pigment responsible for absorbing light energy. It exists in two main forms: chlorophyll a and chlorophyll b. Chlorophyll a is directly involved in the photosynthetic reactions, while chlorophyll b assists by capturing additional light wavelengths, thereby enhancing the efficiency of photosynthesis.

Factors Affecting Photosynthesis

Several factors influence the rate of photosynthesis, including:

Light Intensity: Increased light intensity generally boosts the rate of photosynthesis up to a certain point.
Carbon Dioxide Concentration: Higher $CO_2$ levels can enhance photosynthetic rates.
Temperature: Optimal temperatures facilitate enzyme activity involved in photosynthesis.
Water Availability: Adequate water is essential for the light-dependent reactions.

Understanding these factors is vital for managing agricultural practices and addressing environmental challenges.

Importance of Photosynthesis in the Ecosystem

Photosynthesis is the cornerstone of the Earth's ecosystem. It not only provides the primary energy source for heterotrophic organisms but also maintains atmospheric oxygen levels. Additionally, photosynthesis plays a critical role in the carbon cycle, helping mitigate the effects of greenhouse gases and contributing to climate regulation.

Photosynthesis vs. Cellular Respiration

While photosynthesis and cellular respiration are interconnected, they serve opposite functions:

Photosynthesis: Converts $CO_2$ and $H_2O$ into glucose and releases $O_2$.
Cellular Respiration: Breaks down glucose and $O_2$ to produce $CO_2$, $H_2O$, and energy (ATP).

This cyclical relationship ensures the balance of oxygen and carbon dioxide in the atmosphere.

Photosynthetic Efficiency

Photosynthetic efficiency refers to the conversion rate of light energy into chemical energy. Factors influencing efficiency include pigment composition, light wavelength absorption, and environmental conditions. Enhancing photosynthetic efficiency is a key area of research, aiming to improve crop yields and address food security challenges.

Evolution of Photosynthesis

Photosynthesis has evolved over billions of years, with cyanobacteria being among the earliest organisms to perform oxygenic photosynthesis. The advent of photosynthetic processes significantly altered Earth's atmosphere, paving the way for aerobic life forms. Understanding the evolutionary aspects provides insights into the adaptability and resilience of life on our planet.

Global Significance

On a global scale, photosynthesis affects climate patterns, carbon sequestration, and biodiversity. Forests, oceans, and other ecosystems rely on photosynthetic organisms to sustain ecological balance. Human activities that disrupt photosynthesis, such as deforestation and pollution, have profound implications for environmental health and stability.

Applications of Photosynthesis Principles

The principles of photosynthesis are applied in various fields, including renewable energy, agriculture, and biotechnology. For instance, artificial photosynthesis aims to mimic the natural process to produce sustainable fuels. In agriculture, optimizing photosynthetic rates can lead to increased crop productivity and food sustainability.

Advanced Concepts

Photosynthetic Pathways: C3, C4, and CAM

Plants have evolved different photosynthetic pathways to adapt to varying environmental conditions:

C3 Photosynthesis: The most common pathway where the first product is a three-carbon compound, $3-phosphoglycerate$. It is efficient under cool, moist conditions with normal light.
C4 Photosynthesis: Adapted to high light intensities and temperatures. It involves a four-carbon compound, oxaloacetate, which helps in minimizing photorespiration.
CAM Photosynthesis: Found in arid conditions, where stomata open at night to reduce water loss, fixing $CO_2$ into malate which is stored for use during the day.

Understanding these pathways is essential for comprehending plant adaptability and resilience.

Quantum Mechanics in Photosynthesis

Recent studies have revealed that photosynthesis involves quantum coherence, where excitons (energy carriers) move through the chloroplasts with high efficiency. Quantum tunneling allows excitons to navigate the complex structure of light-harvesting complexes, optimizing energy transfer and minimizing losses. This intersection of quantum mechanics and biology opens new avenues for research in both fields.

Biochemical Pathways and Enzyme Roles

Enzymes play pivotal roles in both the light-dependent and light-independent reactions of photosynthesis. RuBisCO, for example, catalyzes the fixation of $CO_2$ during the Calvin Cycle. The efficiency and regulation of these enzymes are critical for overall photosynthetic productivity. Mutations or environmental stressors that affect enzyme function can significantly impact plant growth and survival.

Genetic Engineering for Enhanced Photosynthesis

Advancements in genetic engineering aim to enhance photosynthetic efficiency by modifying plant genomes. Techniques such as CRISPR-Cas9 allow for precise edits to genes regulating photosynthetic processes. Potential applications include creating crops with higher yields, improved stress resistance, and better nutrient profiles, contributing to global food security.

Interdisciplinary Connections: Photosynthesis and Climate Science

Photosynthesis is intrinsically linked to climate science, particularly in the context of carbon cycling and greenhouse gas dynamics. Photosynthetic organisms act as carbon sinks, sequestering $CO_2$ and mitigating climate change. Integrating knowledge from chemistry, biology, and environmental science is crucial for developing strategies to address global warming and ecosystem degradation.

Photosynthesis and Renewable Energy Technologies

Inspired by natural photosynthesis, researchers are developing artificial systems to harness solar energy. Artificial photosynthesis aims to produce sustainable fuels, such as hydrogen or methanol, by mimicking the light-dependent reactions. These technologies hold promise for reducing reliance on fossil fuels and mitigating environmental impacts.

Photosynthesis in Aquatic Ecosystems

In aquatic environments, photosynthesis is primarily conducted by phytoplankton, algae, and aquatic plants. These organisms contribute significantly to global oxygen production and serve as the base of marine food webs. Factors such as light penetration, water temperature, and nutrient availability influence the photosynthetic activity in these ecosystems.

Impact of Environmental Stressors on Photosynthesis

Environmental stressors like drought, extreme temperatures, and pollutants can adversely affect photosynthetic processes. For instance, high temperatures can denature enzymes involved in the Calvin Cycle, while pollutants like ozone can damage chlorophyll molecules. Understanding these impacts is vital for developing resilient agricultural practices and conserving natural ecosystems.

Innovations in Photosynthetic Research

Innovations such as chlorophyll fluorescence imaging and advanced spectroscopy techniques have enhanced our understanding of photosynthesis. These tools allow scientists to observe and quantify the efficiency of light absorption, energy transfer, and electron transport in real-time. Continued advancements in research methodologies are essential for uncovering the complexities of photosynthetic mechanisms.

Global Carbon Budget and Photosynthesis

Photosynthesis is a critical component of the global carbon budget, influencing atmospheric $CO_2$ levels. By converting $CO_2$ into organic matter, photosynthetic organisms help balance carbon emissions from sources like fossil fuel combustion and deforestation. Accurate modeling of photosynthetic rates is essential for predicting future climate scenarios and informing policy decisions.

Photosynthetic Efficiency Enhancement Strategies

Strategies to enhance photosynthetic efficiency include optimizing light capture, improving enzyme kinetics, and minimizing energy losses during electron transport. Techniques such as breeding for high-yield varieties, implementing precision agriculture, and employing biotechnological interventions are being explored to achieve these enhancements. These strategies aim to increase biomass production and support sustainable agriculture.

Photosynthesis and Human Health

Photosynthesis indirectly affects human health by maintaining oxygen levels and providing essential nutrients through the food chain. Additionally, understanding photosynthetic processes can contribute to medical research, such as developing bio-inspired materials and therapies. The symbiotic relationship between photosynthesis and human well-being underscores its universal importance.

Comparison Table

Aspect	Photosynthesis	Cellular Respiration
Function	Converts light energy into chemical energy	Breaks down glucose to release energy
Reactants	Carbon dioxide and water	Glucose and oxygen
Products	Glucose and oxygen	Carbon dioxide, water, and ATP
Location	Chloroplasts	Mitochondria
Energy Conversion	Light energy to chemical energy	Chemical energy to ATP
Occurrence	In autotrophic organisms (plants, algae)	In all living organisms

Summary and Key Takeaways

Photosynthesis converts $CO_2$ and $H_2O$ into glucose and $O_2$ using light energy.
The process comprises light-dependent reactions and the Calvin Cycle.
Different photosynthetic pathways (C3, C4, CAM) enable plant adaptation to various environments.
Photosynthesis plays a critical role in the global carbon cycle and climate regulation.
Advancements in genetic engineering and renewable technologies are enhancing photosynthetic efficiency.

Examiner Tip

Tips

Remember the acronym "LEC" to recall the main stages of photosynthesis: Light-dependent reactions, Energy conversion, and Calvin Cycle. To differentiate photosynthesis from cellular respiration, think of "Photosynthesis = Produce Glucose", "Respiration = Release Energy." Using visual diagrams can also help reinforce the flow of processes and the transformation of energy.

Did You Know

Did you know that some plants can perform photosynthesis underwater? Aquatic plants like seagrasses have adapted their chloroplasts to capture light in aquatic environments, contributing significantly to oxygen production in oceans. Additionally, the efficiency of photosynthesis varies among different plant species, with some desert plants using specialized mechanisms to survive extreme conditions.

Common Mistakes

Students often confuse the reactants and products of photosynthesis and cellular respiration. For example, they might incorrectly state that photosynthesis produces carbon dioxide instead of oxygen. Another common mistake is misunderstanding the role of chlorophyll, sometimes believing it's responsible for absorbing all wavelengths of light, whereas it primarily absorbs blue and red light.

FAQ

What are the main products of photosynthesis?

The main products of photosynthesis are glucose ($C_6H_{12}O_6$) and oxygen ($O_2$).

Where in the plant cell does photosynthesis take place?

Photosynthesis takes place in the chloroplasts, specifically within the thylakoid membranes and the stroma.

How does light intensity affect the rate of photosynthesis?

Increasing light intensity generally increases the rate of photosynthesis up to a saturation point, beyond which no further increase occurs.

What is the role of chlorophyll in photosynthesis?

Chlorophyll absorbs light energy, which is essential for initiating the light-dependent reactions of photosynthesis.

Why is the Calvin Cycle considered a light-independent reaction?

Because the Calvin Cycle does not require light directly and uses the ATP and NADPH produced during the light-dependent reactions.

1. Acids, Bases, and Salts

1.1 Salt Preparation

1.1.1 Making soluble salts by reaction with excess metal

1.1.2 Making soluble salts by reaction with excess base

1.1.3 Making soluble salts by reaction with excess carbonate

1.1.4 Making soluble salts by titration

1.2 Solubility Rules

1.2.1 Solubility of sodium, potassium, ammonium salts

1.2.2 Solubility of nitrates, chlorides, sulfates, carbonates, and hydroxides

1.3 Hydrated and Anhydrous Salts

1.3.1 Definition of hydrated and anhydrous substances

1.4 Insoluble Salts

1.4.1 Making insoluble salts by precipitation

1.5 Water of Crystallization

1.5.1 Definition and examples (CuSO₄·5H₂O, CoCl₂·6H₂O)

1.6 Properties of Acids

1.6.1 Reaction of acids with metals, bases, and carbonates

1.6.2 Effect of acids on litmus, thymolphthalein, and methyl orange

1.7 Properties of Bases

1.7.1 Definition of bases and alkalis

1.7.2 Reactions of bases with acids and ammonium salts

1.7.3 Effect of alkalis on litmus, thymolphthalein, and methyl orange

1.8 Acids and Alkalis in Aqueous Solution

1.8.1 H⁺ ions in acids, OH⁻ ions in alkalis

1.8.2 Compare acidity and alkalinity using pH and indicators

1.9 Neutralization

1.9.1 Reaction of acids with alkalis to form water

1.10 Strong and Weak Acids

1.10.1 Definition of strong and weak acids

1.10.2 Hydrochloric acid as a strong acid (HCl → H⁺ + Cl⁻)

1.10.3 Ethanoic acid as a weak acid (CH₃COOH ⇌ H⁺ + CH₃COO⁻)

1.11 Oxides

1.11.1 Classify oxides as acidic (e.g., SO₂, CO₂) or basic (e.g., CuO, CaO)

1.11.2 Definition and examples of amphoteric oxides (Al₂O₃, ZnO)

2. Experimental Techniques and Chemical Analysis

2.1 Identification of Ions and Gases

2.1.1 Test for nitrate (NO₃⁻) using aluminum and NaOH

2.1.2 Test for sulfite (SO₃²⁻) using acidified KMnO₄

2.1.3 Cation tests using NaOH and NH₃

2.1.4 Gas tests for NH₃, CO₂, Cl₂, H₂, O₂, SO₂

2.1.5 Flame tests for Li⁺, Na⁺, K⁺, Ca²⁺, Ba²⁺, Cu²⁺

2.1.6 Test for carbonate (CO₃²⁻) using acid

2.1.7 Test for halides (Cl⁻, Br⁻, I⁻) using silver nitrate

2.1.8 Test for sulfate (SO₄²⁻) using barium nitrate

2.2 Experimental Design

2.2.1 Measuring time, temperature, mass, volume

2.2.2 Advantages and disadvantages of methods

2.2.3 Definitions of solvent, solute, solution

2.2.4 Definition of saturated solution

2.2.5 Definition of residue and filtrate

2.3 Acid-Base Titrations

2.3.1 Titration procedure using burette and pipette

2.3.2 Identifying endpoint using indicators

2.4 Chromatography

2.4.1 Paper chromatography for separating mixtures

2.4.2 Identifying substances using chromatograms

2.4.3 Rf value calculation

2.5 Separation and Purification

2.5.1 Filtration, crystallization, distillation

2.5.2 Identifying purity using melting and boiling points

3. Chemical Reactions

3.1 Rate of Reaction

3.1.1 Collision theory: kinetic energy of particles

3.1.2 Collision theory: activation energy

3.1.3 How changes in conditions affect reaction rate

3.1.4 How catalysts lower activation energy

3.1.5 Effect of concentration on reaction rate

3.1.6 Effect of gas pressure on reaction rate

3.1.7 Effect of surface area on reaction rate

3.1.8 Effect of temperature on reaction rate

3.1.9 Effect of catalysts on reaction rate

3.1.10 Definition of catalyst and its role

3.1.11 Methods to measure reaction rate

3.1.12 Interpret graphs of reaction rates

3.1.13 Collision theory: particle concentration

3.1.14 Collision theory: frequency of collisions

3.2 Reversible Reactions and Equilibrium

3.2.1 Definition of reversible reactions

3.2.2 Effect of conditions on reaction direction

3.2.3 Definition of dynamic equilibrium

3.2.4 Effect of temperature on equilibrium

3.2.5 Effect of pressure on equilibrium

3.2.6 Effect of concentration on equilibrium

3.2.7 Effect of catalyst on equilibrium

3.2.8 Haber process equation (N₂ + 3H₂ ⇌ 2NH₃)

3.2.9 Raw materials for Haber process

3.2.10 Conditions used in Haber process

3.2.11 Contact process equation (2SO₂ + O₂ ⇌ 2SO₃)

3.2.12 Raw materials for Contact process

3.2.13 Conditions used in Contact process

3.2.14 Why contact process conditions are used

3.3 Redox

3.3.1 Definition of redox reactions

3.3.2 Oxidation as gain of oxygen, reduction as loss of oxygen

3.3.3 Identify redox reactions using oxygen gain/loss

3.3.4 Definition of oxidation and reduction in terms of electrons

3.3.5 Oxidation and reduction in terms of oxidation numbers

3.3.6 Redox reactions using color changes (MnO₄⁻, I₂)

3.3.7 Definition of oxidizing and reducing agents

3.3.8 Identify oxidizing and reducing agents in reactions

3.3.9 Use of oxidation numbers to identify redox reactions

3.4 Physical and Chemical Changes

3.4.1 Difference between physical and chemical changes

4. Metals

4.1 Corrosion of Metals

4.1.1 Barrier methods (painting, greasing, plastic coating)

4.1.2 How barriers prevent rust (oxygen/water exclusion)

4.1.3 Galvanizing with zinc as protection

4.1.4 Sacrificial protection using reactive metals

4.1.5 Conditions needed for rusting of iron

4.2 Extraction of Metals

4.2.1 Ease of metal extraction depends on reactivity

4.2.2 Blast furnace: iron extracted from hematite

4.2.3 Role of carbon and carbon monoxide in reduction

4.2.4 Thermal decomposition of limestone in furnace

4.2.5 Formation of slag (removes impurities)

4.2.6 Aluminium extraction from bauxite by electrolysis

4.2.7 Blast furnace equations: C + O₂ → CO₂, C + CO₂ → 2CO, Fe₂O₃ + 3CO → 2Fe + 3CO₂

4.2.8 Aluminium extraction: role of cryolite

4.2.9 Why carbon anodes must be replaced in aluminium extraction

4.2.10 Reactions at electrodes in aluminium extraction

4.3 Properties of Metals

4.3.1 Compare physical properties of metals and non-metals

4.3.2 Reactions of metals with acids, water, and oxygen

4.4 Uses of Metals

4.4.1 Uses of aluminium (aircraft, electrical cables, food containers)

4.4.2 Uses of copper (electrical wiring, ductility)

4.5 Alloys

4.5.1 Definition of alloys (mixture of metal with other elements)

4.5.2 Examples: brass (Cu + Zn), stainless steel (Fe + Cr + Ni + C)

4.5.3 Alloys are harder and stronger than pure metals

4.5.4 Why alloys are harder (atoms disrupt layers)

4.6 Reactivity Series

4.6.1 Order of reactivity: K, Na, Ca, Mg, Al, C, Zn, Fe, H, Cu, Ag, Au

4.6.2 Reactions of K, Na, Ca with water

4.6.3 Reaction of Mg with steam

4.6.4 Reactions of Mg, Zn, Fe, Cu, Ag, Au with acids

4.6.5 Explain reactivity based on ion formation

4.6.6 Displacement reactions of metals

4.6.7 Why aluminium appears unreactive (oxide layer)

5. Stoichiometry

5.1 Formulae

5.1.1 Definition of empirical formula

5.1.2 Deduce ionic formula from charges

5.1.3 Write balanced equations with state symbols

5.1.4 Formulae of elements and compounds

5.1.5 Determine formula from atomic ratios

5.1.6 Definition of molecular formula

5.1.7 Write word and symbol equations

5.2 Relative Masses

5.2.1 Definition of relative atomic mass (Ar)

5.2.2 Definition of relative molecular/formula mass (Mr)

5.2.3 Calculate reacting masses (without mole concept)

5.3 The Mole and Avogadro Constant

5.3.1 Concentration in g/dm³ and mol/dm³

5.3.2 Definition of the mole (6.02 × 10²³ particles)

5.3.3 Mole calculations using mass and molar mass

5.3.4 Use molar gas volume (24 dm³ at r.t.p.)

5.3.5 Calculate reacting masses and limiting reactants

5.3.6 Titration calculations (moles, volume, concentration)

5.3.7 Calculate empirical and molecular formulae

5.3.8 Calculate percentage yield and purity

6. Organic Chemistry

6.1 Formulae and Functional Groups

6.1.1 Definition of saturated and unsaturated compounds

6.1.2 Draw and interpret displayed formulae

6.1.3 General formulae for alkanes, alkenes, alcohols, carboxylic acids

6.1.4 Definition of functional groups

6.1.5 Definition of a homologous series

6.2 Naming Organic Compounds

6.2.1 Naming and drawing methane, ethane, ethene, ethanol, ethanoic acid

6.2.2 Identifying organic compounds based on name, formula, or structure

6.3 Fuels

6.3.1 Names of fossil fuels: coal, natural gas, petroleum

6.3.2 Methane as the main component of natural gas

6.3.3 Definition of hydrocarbons

6.3.4 Petroleum as a mixture of hydrocarbons

6.3.5 Fractional distillation of petroleum

6.3.6 Properties of fractions (volatility, boiling points, viscosity)

6.3.7 Uses of petroleum fractions (refinery gas, gasoline, naphtha, kerosene, diesel, fuel oil, lubricatin

6.4 Alkanes

6.4.1 Single covalent bonds in alkanes (saturated hydrocarbons)

6.4.2 Alkanes are generally unreactive except for combustion and substitution

6.5 Alkenes

6.5.1 Double carbon-carbon bonds in alkenes (unsaturated hydrocarbons)

6.5.2 Cracking of large alkanes to produce alkenes and hydrogen

6.5.3 Test for unsaturation using bromine water

6.6 Alcohols

6.6.1 Ethanol production by fermentation of glucose

6.6.2 Ethanol production by catalytic hydration of ethene

6.6.3 Combustion of ethanol

6.6.4 Uses of ethanol (solvent, fuel)

6.7 Carboxylic Acids

6.7.1 Reactions of ethanoic acid with metals, bases, and carbonates

6.7.2 Formation of ethanoic acid by oxidation of ethanol

6.7.3 Ester formation from carboxylic acids and alcohols

6.8 Polymers

6.8.1 Definition of polymers and monomers

6.8.2 Formation of poly(ethene) by addition polymerization

6.8.3 Plastics are made from polymers

6.8.4 Environmental issues of plastics (landfills, ocean waste, toxic gases)

7. States of Matter

7.1 Solids, Liquids, and Gases

7.1.1 Properties of solids, liquids, and gases

7.1.2 Particle arrangement in solids, liquids, and gases

7.1.3 Changes of state: melting, boiling, evaporation, freezing, condensation

7.1.4 Effect of temperature and pressure on gas volume

7.2 Diffusion

7.2.1 Diffusion explained using kinetic particle theory

8. The Periodic Table

8.1 Arrangement of Elements

8.1.1 Periodic Table arranged by atomic number

8.1.2 Change from metallic to non-metallic across a period

8.1.3 Relation of group number to ion charge

8.1.5 Predicting properties using Periodic Table position

8.2 Group I: Alkali Metals

8.2.1 Properties of lithium, sodium, and potassium

8.2.2 Trends down Group I: melting point, density, reactivity

8.2.3 Predict properties of other Group I elements

8.3 Group VII: Halogens

8.3.1 Properties of chlorine, bromine, iodine

8.3.2 Trends down Group VII: density, reactivity

8.3.3 Appearance of halogens at room temperature

8.3.4 Displacement reactions of halogens

8.3.5 Predict properties of other Group VII elements

8.4 Transition Elements

8.4.1 Properties: high density, melting points, colored compounds, catalysts

8.4.2 Variable oxidation states (iron(II) and iron(III))

8.5 Group VIII: Noble Gases

8.5.1 Noble gases are unreactive and monatomic

8.5.2 Explanation of noble gas stability using electron configuration

9. Atoms, Elements, and Compounds

9.1 Elements, Compounds, and Mixtures

9.1.1 Difference between elements, compounds, and mixtures

9.2 Atomic Structure

9.2.1 Structure of an atom (nucleus, electrons, shells)

9.2.2 Relative charges and masses of subatomic particles

9.2.3 Definition of atomic number (proton number)

9.2.4 Definition of mass number (nucleon number)

9.2.5 Electronic configuration for elements (1-20)

9.2.6 Full outer shell in noble gases (Group VIII)

9.2.7 Relation of outer electrons to group number

9.2.8 Relation of electron shells to period number

9.3 Isotopes

9.3.1 Definition of isotopes

9.3.2 Symbols of isotopes (e.g., ₆¹²C, ₁₇³⁵Cl⁻)

9.3.3 Why isotopes have the same chemical properties

9.3.4 Calculating relative atomic mass from isotopes

9.4 Ions and Ionic Bonds

9.4.1 Formation of cations and anions

9.4.2 Definition of ionic bonding

9.4.3 Formation of ionic bonds (dot-and-cross diagrams)

9.4.4 Properties of ionic compounds

9.4.5 Giant lattice structure in ionic compounds

9.5 Simple Molecules and Covalent Bonds

9.5.1 Definition of covalent bonding

9.5.2 Formation of simple covalent molecules (H₂, Cl₂, H₂O, CH₄, NH₃, HCl)

9.5.3 Properties of simple molecular compounds

9.5.4 Dot-and-cross diagrams for CH₃OH, C₂H₄, O₂, CO₂, N₂

9.6 Giant Covalent Structures

9.6.1 Structure of graphite and diamond

9.6.2 Uses of graphite and diamond

9.6.3 Structure of silicon(IV) oxide (SiO₂)

9.7 Metallic Bonding

9.7.1 Definition of metallic bonding

9.7.2 Properties of metals (conductivity, malleability, ductility)

10. Chemistry of the Environment

10.1 Water

10.1.1 Test for water using cobalt(II) chloride and copper(II) sulfate

10.1.2 Test for purity of water using melting and boiling points

10.1.3 Why distilled water is used in chemistry

10.1.4 Substances in natural water (oxygen, metals, plastics, sewage, microbes, fertilizers)

10.1.5 Harmful substances in water (toxins, nitrates, phosphates, microbes)

10.1.6 Water treatment: sedimentation and filtration

10.1.7 Water treatment: activated carbon for odor removal

10.1.8 Water treatment: chlorination to kill microbes

10.2 Fertilizers

10.2.1 Use of ammonium salts and nitrates as fertilizers

10.2.2 NPK fertilizers for nitrogen, phosphorus, potassium supply

10.3 Air Quality and Climate

10.3.1 Composition of clean, dry air (78% N₂, 21% O₂, trace gases)

10.3.2 Sources of CO₂ (fuel combustion), CO (incomplete combustion), CH₄ (decomposition, digestion)

10.3.3 Sources of NOx (car engines), SO₂ (fossil fuels)

10.3.4 Effects of CO₂ and CH₄ (global warming, climate change)

10.3.5 Effects of CO (toxic), particulates (respiratory issues)

10.3.6 Effects of NOx and SO₂ (acid rain, respiratory problems)

10.3.7 How CO₂ and CH₄ cause global warming (heat absorption)

10.3.8 Ways to reduce climate change (trees, hydrogen, renewables)

10.3.9 Reducing acid rain (catalytic converters, low-sulfur fuels, flue gas desulfurization)

10.3.10 Photosynthesis reaction: CO₂ + H₂O → glucose + O₂

10.3.11 Photosynthesis equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

10.3.12 How NOx forms in car engines

10.3.13 How catalytic converters remove NOx (2CO + 2NO → 2CO₂ + N₂)

11. Electrochemistry

11.1 Electrolysis

11.1.1 Definition of electrolysis

11.1.2 Identify anode, cathode, and electrolyte

11.1.3 Electrolysis of molten lead(II) bromide

11.1.4 Electrolysis of concentrated sodium chloride

11.1.5 Electrolysis of dilute sulfuric acid

11.1.6 Products formed at electrodes

11.1.7 Predict products of binary molten compounds

11.1.8 Purpose of electroplating

11.1.9 Process of electroplating metals

11.1.10 Charge transfer in electrolysis (electrons in external circuit)

11.1.11 Charge transfer in electrolysis (ions in electrolyte)

11.1.12 Electrolysis of aqueous copper(II) sulfate (graphite vs copper electrodes)

11.1.13 Predict products for electrolysis of halide solutions

11.1.14 Write ionic half-equations for anode and cathode reactions

11.2 Hydrogen–Oxygen Fuel Cells

11.2.1 Definition of hydrogen–oxygen fuel cell

11.2.2 Advantages and disadvantages of fuel cells vs gasoline engines

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Photosynthesis Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Introduction