Study sheet: Chemical Bonding and Material Properties

📋 Course Outline

1. Photosynthesis and Its Importance
2. Leaf Structure and Plant Nutrition
3. Carbon Movement Through Ecosystems
4. Climate Change and Its Impacts
5. Atomic Structure and Periodic Trends
6. Ions and Chemical Bonding
7. Ionic and Covalent Bonding
8. Giant Structures and Properties
9. Density and Thermal Energy
10. Conservation and Dissipation of Energy
11. Thermal Energy Transfer Mechanisms
12. Cooling by Evaporation
13. Plant Water Transport and Transpiration
14. Human Excretion and Fetal Health
15. Metal Reactivity and Displacement
16. Reactivity and Displacement Reactions
17. Salts and Their Preparation
18. Atoms, Mass and Energy

📅 Key Dates

1. 1817Johann Dobereiner grouped elements in threes according to their properties and appearance in his law of triads.
2. 1864John Newlands arranged the known elements by atomic mass and observed that every eighth element had similar properties, although the pattern did not continue throughout all elements.
3. 1869Dmitri Mendeleev modified Newlands's work by leaving gaps so that elements with similar properties were grouped together and the pattern of eights continued.

📖 1. Photosynthesis and Its Importance

🔑 Key Concepts & Definitions

• Photosynthesis : the process by which plants use light energy to make glucose from water and carbon dioxide, releasing oxygen

★ Must-know

📐 Formula — The word equation for photosynthesis is $\text{water} + \text{carbon dioxide} \rightarrow \text{glucose} + \text{oxygen}$.

• Chlorophyll, a green pigment inside chloroplasts, captures energy from sunlight for photosynthesis.

Further detail

• In a water-plant experiment, the gas released during photosynthesis is collected and tested with a glowing splint, which relights if the gas contains a lot of oxygen.

📌 As light intensity increases, the rate of photosynthesis increases, so a water plant generally produces more bubbles per minute when the lamp is closer.

• About 20% of the air around us is oxygen, much of which is supplied by photosynthesis.

💡 Memory Hook

Light energy + water + carbon dioxide → glucose + oxygen, supporting most life.

📖 2. Leaf Structure and Plant Nutrition

🔑 Key Concepts & Definitions

• Chloroplasts : structures inside plant cells that contain chlorophyll and are the sites of photosynthesis
• Stomata : tiny holes, mainly in the lower epidermis of a leaf, through which carbon dioxide enters and gases diffuse in and out

★ Must-know

• In a leaf, the palisade layer contains cells that do most of the photosynthesis, while the spongy layer contains air spaces and cells that do a small amount of photosynthesis.

• Magnesium is needed to make chlorophyll, so magnesium deficiency causes yellow leaves and reduces photosynthesis.

• Nitrate provides nitrogen needed to convert carbohydrates into proteins and to make chlorophyll, so nitrate deficiency causes dying leaves and small plants.

Further detail

• A leaf can be tested for starch by boiling it, removing its green colour with heated ethanol, softening it in warm water, and adding iodine solution; starch turns blue-black.

💡 Memory Hook

A leaf as a factory: chloroplasts capture light, veins deliver water, and stomata admit carbon dioxide.

📖 3. Carbon Movement Through Ecosystems

🔑 Key Concepts & Definitions

• Carbon Cycle : the movement of carbon atoms between the air, living organisms, decomposers, and fossil fuels

★ Must-know

📐 Formula — The word equation for respiration is $\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water}$.

• Carbon moves through ecosystems when photosynthesis transfers it from air to plants, feeding transfers it to animals, decomposition transfers it to decomposers, and respiration returns carbon dioxide to the air.

📌 Combustion burns fossil fuels so that the carbon in them combines with oxygen from the air to form carbon dioxide.

Further detail

• When organisms die in oxygen-poor places, pressure and heat gradually change their buried remains into fossil fuels such as coal, oil, and natural gas.

📌 Fossil fuels are carbon-containing fuels formed from ancient buried organisms, whereas fossils are the remains or traces of organisms that have turned to rock.

💡 Memory Hook

Air → plant → animal or decomposer → fossil fuel → combustion → air.

📖 4. Climate Change and Its Impacts

🔑 Key Concepts & Definitions

• Greenhouse gas : a gas that traps heat energy in the atmosphere and helps keep Earth warm

★ Must-know

• Extracting and burning fossil fuels releases carbon stored for millions of years into the atmosphere as carbon dioxide.

• Around 67 million years ago, an asteroid collided with Earth, producing dust, reduced sunlight and heat, disrupted food chains, and contributed to a mass extinction.

• Up to three-quarters (75%) of the species alive at the time are thought to have become extinct because of the asteroid collision.

• Increasing carbon dioxide concentration traps more heat near Earth's surface, increasing mean temperature and contributing to more extreme weather, less predictable rainfall, droughts, wildfires and flooding.

• Sea level rises because warmer water expands and melting ice caps and glaciers add water to the oceans.

Further detail

• Sea level has been rising at about 3 mm per year, and more than 600 million people are estimated to be at risk from sea-level flooding by the end of this century.

💡 Memory Hook

More atmospheric carbon dioxide → more trapped heat → climate change and rising sea levels

📖 5. Atomic Structure and Periodic Trends

🔑 Key Concepts & Definitions

• Atomic number : the number of protons in an atom of an element
• Mass number : the total number of protons and neutrons in an atom

★ Must-know

• An atom has no overall charge because it contains equal numbers of positively charged protons and negatively charged electrons, while neutrons have no charge.

• Electrons occupy shells around the nucleus; the first shell holds two electrons, while the second and third shells hold up to eight electrons each.

📌 Elements in Group 1 have one electron in their outermost shell, Group 7 elements have seven, and Group 8 elements have full outermost shells.

Further detail

• A lithium atom with atomic number 3 and mass number 7 contains 3 protons, 3 electrons and 4 neutrons.

• In Group 1, atomic size increases and melting point decreases down the group; lithium melts at 180 °C, sodium at 98 °C and potassium at 63 °C.

💡 Memory Hook

Atomic number → protons → electrons → electron-shell structure

📖 6. Ions and Chemical Bonding

🔑 Key Concepts & Definitions

• Ion : an atom or group of atoms with an electrical charge caused by gaining or losing electrons

★ Must-know

• Atoms react to achieve a more stable arrangement by gaining or losing electrons so that their outermost electron shell becomes full.

📌 Metals such as sodium lose electrons to form positive ions, whereas non-metals such as chlorine gain electrons to form negative ions.

Further detail

• Sodium chloride forms when sodium loses one electron to become Na⁺ and chlorine gains one electron to become Cl⁻; the ions form NaCl through ionic bonding.

📌 Magnesium oxide forms when magnesium becomes Mg²⁺ by losing two electrons and oxygen becomes O²⁻ by gaining two electrons, producing MgO.

• Among lithium, sodium and potassium, potassium is the most reactive because its outer electron is furthest from the nucleus and is lost most easily.

💡 Memory Hook

Metals lose electrons to form positive ions, whereas non-metals gain electrons to form negative ions

📖 7. Ionic and Covalent Bonding

🔑 Key Concepts & Definitions

• Ionic bond : the electrostatic attraction between oppositely charged ions formed when electrons are transferred between a metal and a non-metal
• Covalent bond : a chemical bond formed when atoms share electrons to fill their outermost electron shells

★ Must-know

• 🔄 Magnesium oxide forms through these steps:
  1. A magnesium atom loses two electrons and becomes Mg²⁺.
  2. An oxygen atom gains two electrons and becomes O²⁻.
  3. The oppositely charged ions attract each other to form magnesium oxide.

Further detail

• Hydrogen chloride has the formula HCl because hydrogen and chlorine share one pair of electrons.

• Ammonia has the formula NH₃ because three hydrogen atoms share three pairs of electrons with one nitrogen atom.

💡 Memory Hook

Ionic bonds transfer electrons, whereas covalent bonds share electrons.

📖 8. Giant Structures and Properties

🔑 Key Concepts & Definitions

• Lattice : a giant regular structure of ions held together by electrostatic forces in an ionic compound

★ Must-know

📌 Ionic substances have very high melting and boiling points because strong electrostatic forces hold their ions together, whereas simple covalent substances have low melting and boiling points because weak intermolecular forces act between their molecules.

• Diamond is very hard because each carbon atom forms four strong covalent bonds in a rigid three-dimensional structure.

• Graphite is soft because each carbon atom bonds to three others in layers whose weak interlayer bonds allow the layers to slide over one another.

📌 Ionic compounds conduct electricity when melted or dissolved in water because their charged ions are free to move, whereas simple covalent molecules do not conduct electricity.

Further detail

• In sodium chloride, each Na⁺ ion is surrounded by six Cl⁻ ions arranged in a regular pattern, producing crystals with a regular shape.

💡 Memory Hook

Diamond is hard because its bonds form a rigid network, whereas graphite is soft because its layers slide.

📖 9. Density and Thermal Energy

🔑 Key Concepts & Definitions

• Density : the mass per unit volume of a substance

★ Must-know

• Mendeleev predicted the properties of some undiscovered elements that would fill the gaps in his periodic table, and the predictions were correct. — Dmitri Mendeleev, 1869

📐 Formula — Density is calculated using $\text{density}=\frac{\text{mass}}{\text{volume}}$.

📌 An object more dense than water sinks, while an object less dense than water floats.

📌 Heat is the total thermal energy of all particles in an object, whereas temperature is the average energy of its particles.

Further detail

• The volume of an irregular object is found by measuring the increase in water volume when the object is placed in a measuring cylinder.

• Gases have lower densities than liquids and solids because their particles are farther apart.

• Absolute zero is −273 °C, the lowest possible temperature at which particles would reach their minimum motion.

💡 Memory Hook

More mass in the same volume increases density; greater density than water causes sinking.

📖 10. Conservation and Dissipation of Energy

🔑 Key Concepts & Definitions

• System : Something chosen to be studied, especially in terms of energy changes.

★ Must-know

📌 The law of conservation of energy states that energy cannot be created or destroyed, only changed or transferred.

• In an electric lamp, every 100 J of electrical energy supplied produces 10 J of light energy and 90 J of thermal energy, so the total output remains 100 J.

📌 Dissipated energy spreads into the surroundings and becomes less useful, whereas destroyed energy would no longer exist; energy is dissipated but never destroyed.

📌 Thermal energy always transfers from a hotter place to a colder place, and the transfer rate increases when the temperature difference is greater.

Further detail

• When thermal energy is removed from a hot object and spreads into a colder place, the thermal energy is said to have dissipated.

💡 Memory Hook

Energy transfer or storage changes its form, but conservation keeps the total constant.

📖 11. Thermal Energy Transfer Mechanisms

🔑 Key Concepts & Definitions

• Conduction : The transfer of thermal energy through vibrating particles pushing against neighbouring particles.
• Radiation : The transfer of thermal energy by invisible waves that does not require particles.

★ Must-know

• In convection, heated liquid or gas expands, becomes less dense and rises, while colder, denser material sinks and is heated in turn, producing a convection current.

• Dull, black surfaces with a large surface area are the best emitters and absorbers of thermal radiation, while shiny, white or silver surfaces with a small surface area are the worst.

Further detail

📐 Formula — Density is given by $\text{density}=\frac{\text{mass}}{\text{volume}}$, so increasing volume while mass stays constant decreases density.

• A vacuum flask reduces thermal transfer because its vacuum prevents conduction and its silver surface reflects radiation back toward the hot drink.

💡 Memory Hook

CCR: Conduction, Convection, Radiation.

📖 12. Cooling by Evaporation

🔑 Key Concepts & Definitions

• Evaporation : The change of state from liquid to gas that occurs when some high-energy particles escape from a liquid surface.

★ Must-know

• During evaporation, the highest-energy particles leave the liquid, lowering the average energy of the particles that remain and therefore lowering the liquid's temperature.

• Sweat cools the skin because thermal energy from the skin supplies the energy needed for sweat to evaporate, causing the skin to lose thermal energy.

Further detail

📌 In very humid conditions, sweat may not evaporate effectively, so body temperature can increase because the evaporative cooling effect is reduced.

📌 A liquid with weaker forces between its particles evaporates faster and feels colder than a liquid with stronger particle forces at the same temperature.

💡 Memory Hook

High-energy particles escape → the average particle energy falls → the liquid cools.

📖 13. Plant Water Transport and Transpiration

🔑 Key Concepts & Definitions

• Root hairs : specialized cells that provide a large surface area for absorbing water and mineral ions from the soil.
• Xylem vessels : long, hollow tubes made from dead cells whose walls remain to transport water from roots to the highest parts of a plant.
• Transpiration : the loss of water vapour from plant leaves through the stomata.

★ Must-know

• 🔄 Water moves through the plant in this order:

  1. from the soil into root hair cells
  2. across the root
  3. into xylem vessels
  4. up through the roots and stem
  5. into the leaves

• 🔄 Water vapour leaves a leaf through these stages: water leaves the xylem and enters leaf cells, water evaporates from the cellulose cell walls, water vapour diffuses through air spaces, water vapour exits through the stomata

Further detail

• Plants need water for:
  • cell support
  • transport of dissolved mineral salts
  • cooling by evaporation
  • photosynthesis

💡 Memory Hook

Roots → xylem → leaves → stomata

📖 14. Human Excretion and Fetal Health

🔑 Key Concepts & Definitions

• Excretion : the removal of waste substances made in cells or substances present in excess that have been inside the body.
• Fetus : a developing human before birth that depends on the mother for substances needed and removal of excretory substances.

★ Must-know

• Human excretory substances include:

  • carbon dioxide made during respiration
  • urea made in liver cells
  • excess water

• 🔄 Urine passes through the excretory system in this order: the kidneys filter urea and excess water from the blood, urea dissolves in the excess water to form urine, urine travels through the ureters, urine is stored in the bladder, urine leaves through the urethra

• The mother’s and fetus’s blood do not mix; needed substances diffuse from the mother’s blood to the fetus’s blood, while fetal excretory substances diffuse in the opposite direction.

📌 Carbon monoxide from smoking reduces the oxygen that haemoglobin can transport, so fetal cells receive less oxygen and may develop less normally.

Further detail

• Recommendations during pregnancy include:
  • check drugs with a doctor or pharmacist
  • stop smoking
  • avoid alcohol
  • avoid illegal drugs
  • avoid drinking a lot of coffee or cola

💡 Memory Hook

Liver makes urea → kidneys filter blood → urine carries it out

📖 15. Metal Reactivity and Displacement

🔑 Key Concepts & Definitions

• Reactivity series : an arrangement of metals from the most reactive at the top to the least reactive at the bottom.

★ Must-know

📌 A more reactive metal can displace a less reactive metal from a solution of its salt.

Further detail

• Potassium reacts very vigorously with cold water, zinc reacts with steam but not water, and copper shows no reaction with steam or water.

• Zinc reacts with sulfuric acid to form zinc sulfate and hydrogen.

• Magnesium reacts with oxygen to form magnesium oxide.

💡 Memory Hook

A more reactive metal displaces a less reactive metal from its salt solution

📖 16. Reactivity and Displacement Reactions

🔑 Key Concepts & Definitions

• Reactivity series : a list of metals arranged from the most reactive at the top to the least reactive at the bottom
• Displacement reaction : a reaction in which a more reactive metal replaces a less reactive metal in a salt

★ Must-know

• Iron displaces copper from copper sulfate: $\mathrm{CuSO_4 + Fe \rightarrow FeSO_4 + Cu}$.

📌 A metal can displace another metal from its salt only when the first metal is more reactive than the second metal.

Further detail

• 🔄 A mystery metal can be identified by: observing its appearance, testing its reactions with water, oxygen and dilute acid, comparing displacement reactions with metals in the reactivity series

• In the thermite reaction, aluminium displaces iron from iron oxide to produce aluminium oxide and molten iron, releasing enough energy to weld railway rails.

• Carbon displaces these metals from their ores:

  • zinc
  • iron
  • tin
  • lead

💡 Memory Hook

More reactive metals displace less reactive metals; less reactive metals cannot displace more reactive metals.

📖 17. Salts and Their Preparation

🔑 Key Concepts & Definitions

• Salt : a compound such as sodium chloride, copper sulfate, silver nitrate or calcium carbonate that can be formed from an acid

★ Must-know

• The acid families are:
  • hydrochloric acid forms chlorides
  • sulfuric acid forms sulfates
  • nitric acid forms nitrates
  • carbonic acid forms carbonates
  • citric acid forms citrates

📐 Formula — A metal reacts with an acid according to $\text{acid} + \text{metal} \rightarrow \text{salt} + \text{hydrogen}$.

📐 Formula — A metal oxide reacts with an acid according to $\text{metal oxide} + \text{acid} \rightarrow \text{salt} + \text{water}$.

📐 Formula — An acid reacts with a carbonate according to $\text{acid} + \text{carbonate} \rightarrow \text{salt} + \text{water} + \text{carbon dioxide}$.

📐 Formula — Neutralisation occurs when an acid reacts with an alkali to form a salt and water: $\text{acid} + \text{alkali} \rightarrow \text{salt} + \text{water}$.

Further detail

📌 A base is a metal oxide, while an alkali is a soluble metal base that forms an alkaline solution when dissolved in water.

💡 Memory Hook

Metal + acid, metal oxide + acid, carbonate + acid, then acid + alkali.

📖 18. Atoms, Mass and Energy

🔑 Key Concepts & Definitions

• Law of conservation of mass : mass is neither gained nor lost in a chemical reaction because the atoms are rearranged rather than created or destroyed
• Exothermic reaction : releases more energy when product bonds form than is needed to break reactant bonds
• Endothermic reaction : requires more energy to break reactant bonds than is released when product bonds form
• Law of conservation of energy : energy cannot be created or destroyed, although it can be transferred from one form to another during a chemical reaction
• Amplitude : the maximum distance that particles move from their position when there is no wave
• Frequency : the number of complete vibrations that happen each second, measured in hertz (Hz)
• Interference : the effect produced when waves meet each other
• Collision theory : a newly formed planet about the size of Mars collided with the newly formed Earth, producing rocks and dust that gathered by gravity to form the Moon
• Nebula : a cloud of dust and gas in space, containing mostly hydrogen and a smaller quantity of helium

📝 Essential Points

• 🔄 During a chemical reaction,:

  1. atoms in the reactants separate or combine
  2. the atoms form new arrangements
  3. no atoms are lost or newly produced

• When magnesium burns, oxygen from the air combines with it to form magnesium oxide, so the product has greater mass than the original magnesium.

📌 As the amplitude of a sound wave increases, the loudness of the sound increases.

📌 As the frequency of a sound wave increases, the pitch of the sound increases.

• 🔄 Reinforcement occurs when:

  1. the peaks meet together
  2. the troughs meet together
  3. the amplitudes add together
  4. the sound becomes louder

• Two sound waves cancel completely when the peak of one meets the trough of another with equal amplitude, causing zero amplitude and no sound.

• For two sound waves to cancel completely, their frequencies and amplitudes must be the same.

💡 Memory Hook

Atoms rearrange, so mass is conserved; bonds break and form, so energy is transferred.

📊 Synthesis Tables

Photosynthesis and Respiration

Process	Reactants	Products	Effect on Carbon Dioxide
Photosynthesis	Water and carbon dioxide	Glucose and oxygen	Removes carbon dioxide
Respiration	Glucose and oxygen	Carbon dioxide and water	Releases carbon dioxide

Periodic Table Group Trends

Group	Outer-shell structure	Key properties
Group 1	One outer electron	Atomic size increases and melting point decreases down the group
Group 7	Seven outer electrons	Reactivity decreases from fluorine to bromine
Group 8	Full outer shell	Gases that are inert and do not form compounds