National Year 10 Combined Science: Trilogy
Chapters: 13
1. 4.1 Cell biology
4.1.1 Cell structure · 4.1.2 Cell division · 4.1.3 Transport in cells
- The Cell: Basic Unit of Life – Every living thing is made of cells. Robert Hooke first saw cells in cork in 1665. Cells are prokaryotic (no true nucleus, like bacteria) or eukaryotic (true nucleus). Plant cells have a cell wall, chloroplasts and a big vacuole; animal cells do not. Each organelle has a job. Water enters and leaves cells by osmosis. Cells make new cells by mitosis (growth) and meiosis (sex cells).
- Cell Cycle and Cell Division – A cell grows, copies its DNA and splits in a fixed order called the cell cycle: interphase (G1, S, G2) and M phase. In S phase the DNA doubles (2C → 4C) but the chromosome number stays the same. Mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis give two cells identical to the parent – it is an equational division used for growth and repair. Meiosis has two divisions; in meiosis I homologous chromosomes pair, cross over and separate, halving the chromosome number (2n → n). It makes four haploid cells for gametes and creates variation.
- Membrane Transport: How Things Get In and Out of a Cell – The cell membrane is a thin double layer of fat-like molecules with proteins in it. It lets some substances through and stops others (selectively permeable). Diffusion moves particles from high to low concentration with no energy. Facilitated diffusion does the same through protein channels. Osmosis is the diffusion of water through a partially permeable membrane. Active transport uses ATP and a protein pump to move particles from low to high concentration. Very large things enter and leave in bubbles (endocytosis and exocytosis).
2. 4.2 Organisation
4.2.1 Principles of organisation · 4.2.2 Animal tissues, organs and organ systems · 4.2.3 Plant tissues, organs and systems
- Tissues: Plant and Animal Tissues – A tissue is a group of similar cells that do one job together. Cells form tissues, tissues form organs, organs form organ systems and systems form an organism. Plants have dividing meristematic tissue and non-dividing permanent tissue, including xylem (water up) and phloem (food both ways). Animals have epithelial, connective, muscular and nervous tissue. Bones, muscles and joints need good posture, exercise and food rich in calcium.
- Human Body Systems – Your body is organised in levels: cells make tissues, tissues make organs, organs make organ systems, and all systems together make you, the organism. Each system has a main job: skeletal (frame), muscular (movement), circulatory (transport), respiratory (gas exchange), digestive (food), excretory (waste), nervous and endocrine (control), immune (defence), integumentary (skin, hair, nails) and reproductive. No system works alone: during exercise the muscles, heart, lungs and nerves all change together to keep the inside of the body steady (homeostasis).
3. 4.3 Infection and response
4.3.1 Communicable diseases
- Infectious Diseases: How Germs Spread and How We Stop Them – An infectious (communicable) disease is caused by a tiny living thing called a pathogen: a bacterium, virus, fungus or protist. It passes from one person to another through air, water and food, touch, or a vector such as a mosquito. The body fights back with skin, mucus, stomach acid and white blood cells. Vaccines train the immune system in advance. Hand washing, clean water, cooking food well, mosquito nets and staying home when sick all cut the spread.
4. 4.4 Bioenergetics
4.4.1 Photosynthesis · 4.4.2 Respiration
- Life Processes and Photosynthesis – Life processes are the jobs every living body must keep doing to stay alive: nutrition, respiration, transport and excretion. Green plants do nutrition by photosynthesis: using sunlight and chlorophyll, they turn carbon dioxide and water into glucose and give out oxygen.
- Respiration: Aerobic, Anaerobic and the Human Lungs – Respiration is the breakdown of food, usually glucose, inside cells to release energy, stored as ATP. With oxygen (aerobic) glucose is fully broken into carbon dioxide and water and gives much energy; without oxygen (anaerobic) it gives little energy and makes ethanol (yeast) or lactic acid (muscles). Our lungs bring oxygen to the blood through millions of alveoli.
5. 5.1 Atomic structure and the periodic table
5.1.1 A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes · 5.1.2 The periodic table
- Structure of the Atom – An atom has a tiny, heavy, positive nucleus made of protons and neutrons. Electrons move around it in fixed shells K, L, M, N. The number of protons (Z) tells the element; protons + neutrons give the mass number (A). Outer electrons decide valency. Isotopes share Z; isobars share A.
- The Periodic Table: Groups, Periods and Trends – The periodic table lists elements in order of atomic number (number of protons). Rows are periods; columns are groups. Elements in the same group have the same number of outer-shell electrons, so they react in similar ways. Mendeleev built an early table, left gaps for unknown elements and predicted their properties. Metals are on the left and bottom, non-metals on the right and top. Group 0 noble gases have full outer shells and are unreactive. Group 1 alkali metals get more reactive going down. Group 7 halogens get less reactive going down.
6. 5.2 Bonding, structure, and the properties of matter
5.2.1 Chemical bonds, ionic, covalent and metallic · 5.2.2 How bonding and structure are related to the properties of substances · 5.2.3 Structure and bonding of carbon
- Chemical Bonding: Ionic, Covalent and Metallic Bonds – Atoms join together (bond) to become more stable. Only their outer electrons take part. Most atoms are most stable with 8 outer electrons: the octet rule. There are three main ways to reach it. In an ionic bond, a metal gives electrons to a non-metal, making oppositely charged ions that attract. In a covalent bond, two non-metals share pairs of electrons to make molecules. In a metallic bond, metal atoms release outer electrons into a shared 'sea' that holds positive ions together. The difference in electronegativity (how strongly an atom pulls shared electrons) tells us which kind of bond forms. The type of bond explains melting points, whether a substance conducts electricity, and whether it dissolves in water.
- How Structure Decides the Properties of Substances – The way particles are held together decides how a substance behaves. Ionic and giant covalent substances have strong bonds all through, so they melt very high. Small molecules have weak forces between molecules, so they melt and boil low. Metals have free electrons, so they conduct.
- Allotropes of Carbon: Diamond, Graphite, Graphene and Fullerenes – Allotropes are different forms of the same element in the same state. Carbon has several. In diamond each atom makes 4 strong covalent bonds in a giant 3D network, so it is very hard, has a very high melting point and does not conduct electricity. In graphite each atom bonds to 3 others in flat layers of hexagons; the layers slide (soft, slippery) and one spare electron per atom is free to move, so graphite conducts. Graphene is a single graphite layer: strong, light and an excellent conductor. Fullerenes such as C₆₀ are hollow cages; nanotubes are rolled-up tubes. All of them burn in oxygen to make carbon dioxide.
7. 5.3 Quantitative chemistry
5.3.1 Chemical measurements, conservation of mass and quantitative interpretation of equations · 5.3.2 Use of amount of substance in relation to masses of pure substances
- Atoms and Molecules – In a chemical reaction mass is neither created nor destroyed (conservation of mass), and a compound always has its elements in the same ratio by mass (constant proportions). Dalton explained both: matter is made of tiny atoms that join in small whole numbers. Atoms join to form molecules; charged atoms or groups are ions. Formulae are written by crossing valencies. Molecular mass (or formula unit mass for ionic compounds) is the sum of the atomic masses in the formula, in u.
- Moles: Counting Particles by Weighing – A mole is a fixed number of particles: 6.02 × 10²³ (the Avogadro constant). One mole of a substance has a mass in grams equal to its relative formula mass (Mr). So moles = mass ÷ Mr. Balanced equations tell you the ratio of moles that react, and the reactant that runs out first is the limiting reactant.
8. 5.4 Chemical changes
5.4.1 Reactivity of metals · 5.4.2 Reactions of acids · 5.4.3 Electrolysis
- Corrosion, Its Prevention and Alloys – Corrosion is the slow eating away of a metal by air, moisture or chemicals around it. Iron rusts only when both air (oxygen) and water are present, forming hydrated iron oxide. It can be prevented by painting, oiling, galvanising, chrome plating, anodising or making alloys. An alloy is a uniform mixture of a metal with other metals or a non-metal; alloys are usually harder, stronger and more corrosion-resistant than the pure metal.
- Occurrence and Extraction of Metals – Metals are found in the earth's crust, mostly as compounds called minerals; a mineral from which a metal can be taken out profitably is an ore. Extraction has three stages: enrichment (removing gangue), getting the crude metal (roasting or calcination, then reduction or electrolysis, chosen by the metal's place in the reactivity series), and refining (usually electrolytic).
- Ionic Compounds: How Metals and Non-metals React – A metal atom gives its outer electrons to a non-metal atom so that both get a full outer shell (octet). The metal becomes a positive ion (cation), the non-metal a negative ion (anion), and the strong pull between them is an ionic (electrovalent) bond. Ionic compounds are hard crystalline solids with high melting points, dissolve in water, and conduct electricity only when molten or dissolved.
- Metals and Non-metals: Properties and the Reactivity Series – Metals are usually shiny, hard, malleable, ductile and good conductors; non-metals are usually dull, brittle and poor conductors. Metals form basic oxides, react with water and dilute acids (giving hydrogen) and a more reactive metal pushes a less reactive one out of its salt solution. Listing metals from most to least reactive gives the reactivity series.
- Acids and Bases: Properties, Indicators and Reactions – An acid gives H⁺ ions in water and a base gives OH⁻ ions. Indicators show which one is present by a colour or smell change, and when H⁺ meets OH⁻ they make water, leaving a salt behind.
- Electrolysis: Splitting Compounds with Electricity – Electrolysis uses a direct current to break down an ionic compound that is melted or dissolved (the electrolyte). Positive ions move to the cathode (−) and gain electrons (reduction). Negative ions move to the anode (+) and lose electrons (oxidation). Molten compounds give the metal and the non-metal. In solutions, water also gives H⁺ and OH⁻: hydrogen forms at the cathode unless the metal is less reactive than hydrogen, and oxygen forms at the anode unless a halide is present. Reactive metals like aluminium are extracted by electrolysis.
9. 5.5 Energy changes
5.5.1 Exothermic and endothermic reactions
- Exothermic and Endothermic Reactions – Energy is conserved in every reaction; it only moves between the chemicals and the surroundings. An exothermic reaction transfers energy to the surroundings, so the temperature rises (burning, neutralisation, respiration, hand warmers). An endothermic reaction takes energy in, so the temperature falls (thermal decomposition, citric acid + sodium hydrogencarbonate, photosynthesis, cold packs). A reaction profile shows reactants, products and the activation energy (the minimum energy needed to react). Breaking bonds takes energy in; making bonds gives energy out. ΔH = energy to break bonds − energy released making bonds; negative means exothermic.
10. 6.1 Energy
6.1.1 Energy changes in a system and ways energy is stored · 6.1.2 Conservation and dissipation of energy · 6.1.3 National and global energy resources
- Work, Energy and Power – Work is done when a force moves an object: W = F × s, measured in joules (J). Energy is the ability to do work. A moving body has kinetic energy ½mv²; a raised body has potential energy mgh. Energy is never made or destroyed, only changed from one form to another. Power is how fast work is done: P = W ÷ t, in watts. Simple machines like levers and pulleys let a small effort move a big load.
- Minerals and Energy Resources – Minerals are natural substances found in rocks. They are metallic (ferrous or non-ferrous), non-metallic, or energy minerals. Energy comes from conventional sources like coal, petroleum, natural gas and electricity, and from non-conventional sources like sun, wind, nuclear, biogas, tides and heat from the Earth. Both minerals and energy must be conserved.
11. 6.2 Electricity
6.2.1 Current, potential difference and resistance · 6.2.2 Series and parallel circuits · 6.2.3 Domestic uses and safety · 6.2.4 Energy transfers
- Ohm's Law – At constant temperature, the current through a conductor is directly proportional to the potential difference across it: V = I × R. R is the resistance, measured in ohms (Ω); 1 Ω = 1 V/1 A. The V–I graph of an ohmic conductor is a straight line through the origin.
- Resistors in Series and Parallel – In series, resistors form one path: the same current flows through each, voltages add up and R_s = R₁ + R₂ + R₃. In parallel, each resistor gets its own branch: the voltage across each is the same, currents add up and 1/R_p = 1/R₁ + 1/R₂ + 1/R₃, so R_p is smaller than the smallest resistor.
- Domestic Electric Circuits – A house gets 220 V, 50 Hz AC through a live and a neutral wire; appliances are joined in parallel on separate 5 A and 15 A circuits, and a fuse or MCB in the live wire plus an earth wire keep the house safe.
- Electric Power and Electrical Energy – Electric power is the rate of using electrical energy: P = VI = I²R = V²/R, in watts. Energy used = power × time. At home energy is measured in kilowatt-hours: 1 kWh = 1 unit = 3.6 × 10⁶ J. Bill = units × rate.
12. 6.3 Particle model of matter
6.3.1 Changes of state and the particle model · 6.3.2 Internal energy and energy transfers · 6.3.3 Particle model and pressure
- The Particle Model of Matter – All matter is made of tiny particles that are always moving. In a solid they are close and only vibrate; in a liquid they are close but slide past each other; in a gas they are far apart and move fast in all directions. Heating gives particles more energy: either they move faster (temperature rises) or the forces between them are broken (the state changes while the temperature stays the same). Gas pressure comes from particles hitting the walls.
- Internal Energy – Everything is made of tiny particles. They move (kinetic energy) and are held by forces between them (potential energy). The total of all these energies is the internal energy U. Heating a substance raises its internal energy: either the particles move faster (temperature rises, Q = mcΔT) or bonds are broken (state changes at constant temperature, Q = mL). Doing work on it, like rubbing or squashing, also raises U.
- Gas Laws: How Pressure, Volume and Temperature Are Linked – Gas pressure comes from particles hitting the walls. For a fixed amount of gas: Boyle's law P₁V₁ = P₂V₂ (constant T); Charles's law V₁/T₁ = V₂/T₂ (constant P); pressure (Gay-Lussac's) law P₁/T₁ = P₂/T₂ (constant V). Temperature must be in kelvin. Combined: P₁V₁/T₁ = P₂V₂/T₂. Dalton's law: in a mixture, total pressure = sum of partial pressures, and each partial pressure = mole fraction × total pressure.
13. 6.4 Atomic structure
6.4.1 Atoms and isotopes · 6.4.2 Atoms and nuclear radiation
- Structure of the Atom – An atom has a tiny, heavy, positive nucleus made of protons and neutrons. Electrons move around it in fixed shells K, L, M, N. The number of protons (Z) tells the element; protons + neutrons give the mass number (A). Outer electrons decide valency. Isotopes share Z; isobars share A.
- Radioactivity: Alpha, Beta, Gamma and Half-Life – Some atomic nuclei are unstable. They give out radiation at random to become more stable. This is radioactive decay. Alpha (2 protons + 2 neutrons), beta (a fast electron) and gamma (a wave of energy) are the three main kinds. Half-life is the time for half of the unstable nuclei to decay.