Comprehensive Knowledge Organiser: Science Year 7 and 8

Acids and Alkalis (Year 7)

• Key Scientific Words and Definitions:     * Hazard: Something that could cause harm.     * Risk: The likelihood that a hazard will cause damage or harm.     * Precaution: Action taken to reduce risk of harm from a hazard.     * Solution: Formed when a substance dissolves in a liquid.     * Acid: A substance with a pH of less than $7$. The lower the pH, the more acidic the solution.     * Alkali: A substance that can dissolve in water to give a solution with a pH of more than $7$. The higher the pH, the more alkaline the solution.     * Neutral: Substance that is neither acidic or alkaline. It has a pH of $7$.     * Dilute: To add water to a solution to make it less concentrated.     * pH scale: A numerical scale that goes from $0$ to $14$ that shows how acidic or alkaline a substance is.     * Indicators: A substance that changes different colours depending upon the pH of the solution it is in.     * Neutralisation: A reaction in which an acid and alkali (base) react to produce a salt and water only.     * Base: Any substance, soluble or insoluble in water, that neutralises an acid.     * Salt: A compound containing a metal and a non-metal.

• Safety and Symbols:     * Symbols show the type of harm caused by a substance.     * Risks can be reduced by taking precautions. Examples include:         * Wearing eye protection to prevent chemicals splashing in your eyes.         * Tying long hair back to prevent it catching fire in a Bunsen flame.

• Acids in the Laboratory:     * Hydrochloric acid ($HCl$)     * Sulfuric acid ($H_2SO_4$)     * Nitric acid ($HNO_3$)

• Neutralisation Reactions and Salt Formation:     * General Equation: $\text{ACID} + \text{BASE} \rightarrow \text{SALT} + \text{WATER}$     * Reaction Components: Reactants are on the left, Products are on the right.     * Naming Convention for Salts:         * The first part of the salt name is the same as the metal in the alkali or base.         * The second part of the salt name comes from the acid.     * Specific Acid-to-Salt Second Names:         * Hydrochloric acid ($HCl$) produces a chloride.         * Sulfuric acid ($H_2SO_4$) produces a sulfate.         * Nitric acid ($HNO_3$) produces a nitrate.     * Examples of Neutralisation Reactions:         * $magnesium\,hydroxide + hydrochloric\,acid \rightarrow magnesium\,chloride + water$         * $lithium\,hydroxide + sulfuric\,acid \rightarrow lithium\,sulfate + water$         * $zinc\,oxide + nitric\,acid \rightarrow zinc\,nitrate + water$         * $Sulfuric\,acid + copper\,oxide \rightarrow copper\,sulfate + water$

• Everyday Applications of Neutralisation:     * Antacids: Medicines taken if people have indigestion caused by too much acid in the stomach. The antacid contains a base to neutralise the acid.     * Soil Treatment: Soil can become too acidic for some crops to grow. Farmers spread lime (calcium oxide, which is a base) on the soil to neutralise the acid.     * Toothpaste: Contains a mild alkali to neutralise the acid in the mouth.

• Scientific Graphing Rules:     * Mnemonic (Dairy Milk): Dependent variable is what we Measure. It is plotted on the vertical y-axis.     * Mnemonic (Ice Cream): Independent variable is what we Choose to Change.     * Graph Titles: Written in the form: ‘How [dependent variable] depends on [independent variable]’.     * Example: "How the pH depends on the type of soft drink".

Food and Nutrition (Year 8)

• Key Scientific Words and Definitions:     * Diet: The food that you eat.     * Nutrients: Substances needed in the diet to provide raw materials for making new materials and for energy release.     * Constipation: When the intestines get blocked.     * Absorb: To soak up or take in.     * Bias: A shift away from a correct meaning or value.     * Deficiency disease: A disease caused by a lack of a nutrient.     * Malnutrition: A problem caused by having too much or too little of a nutrient in the diet.     * Soluble: Describes a substance that can dissolve in a liquid.     * Enzymes: Substances that can speed up some processes in living cells, such as breaking down food molecules.     * Diffusion: When particles spread and mix with each other without anything moving them.

• Food Testing Procedures:     * Starch: Add $2$ drops of iodine solution.         * Positive result: Blue/Black.         * Negative result: Yellow/brown.     * Fats: Rub a small dry food sample on some white paper. Fats will leave a greasy, translucent mark on the paper.     * Proteins: Place a $1\,cm^3$ food sample in a test tube and add $5$ drops of Biuret solution.         * Positive result: Purple.         * Negative result: Blue.

• Deficiency Diseases and Malnutrition:     * Kwashiorkor: Caused by a lack of protein. Symptoms include a ‘pot belly’ caused by fluids collecting around intestines and weak muscles that cannot hold the stomach in.     * Night blindness: Caused by a lack of Vitamin A. Symptoms include an inability to see well at night.     * Scurvy: Caused by a lack of Vitamin C. Symptoms include painful joints and bleeding gums.     * Rickets: Caused by a lack of Vitamin D. Symptoms include bent legs due to weak bones that do not form properly.     * Anaemia: Caused by a lack of Iron. Symptoms include tiredness and shortness of breath.     * Obesity: Caused by too much fat, which may cause heart disease; very overweight people are described as obese.     * Starvation: Caused by eating too little, leading to weakness. Both starvation and obesity are forms of malnutrition.

• The Digestive System: Organs and Functions:     * Mouth: Contains teeth to chew food to make it smaller.     * Salivary gland: Produces enzymes to break down food.     * Oesophagus: A tube connecting the mouth to the stomach; muscles contract to push food down.     * Liver: Produces bile that emulsifies fat (turning large droplets into smaller droplets) and reduces the pH of the stomach.     * Gall bladder: Stores bile.     * Stomach: Produces hydrochloric acid to kill bacteria and produces enzymes to break down food.     * Pancreas: Produces enzymes to break down food.     * Small intestine: Absorbs nutrients and produces enzymes; specialized for diffusion.     * Large intestine: Absorbs water.     * Anus: Where faeces exits the body.

• Adaptations of the Small Intestine:     * The wall is folded and covered with villi to provide a large surface area.     * Cells have microvilli to increase surface area further.     * The wall is only one-cell thick, facilitating easier diffusion into the blood.     * A good blood supply allows fast diffusion; digested molecules are carried in the blood plasma.

Periodic Table (Year 8)

• Key Scientific Words and Definitions:     * Chemical reaction: A change in which one or more new substances are formed.     * Physical change: A change in which no new substances are formed (e.g., changes of state).     * Group: A vertical column of elements. Elements in the same group generally have similar properties.     * Period: A process in which energy is released from substances so it can be used by an organism. (Note: Transcript definition deviates from standard chemical 'period').     * Chemical formula: A combination of symbols and numbers showing the count of atoms of different elements in a molecule or the ratio of elements in a compound regardless of molecular structure.     * Halogen: An element in group $7$ of the periodic table, such as fluorine and chlorine.     * Alkali Metal: A group of very reactive metals found in group $1$.     * Noble gas: A group of very unreactive non-metal gases found in group $0$.     * Anomalous Result: A measurement that doesn’t fit the same pattern as other measurements in an experiment.     * Range: The difference between the highest and lowest values in a data set (ignoring anomalies).

• Dalton’s Atomic Theory:     * All matter is made up of tiny particles called atoms.     * Atoms are indestructible and cannot be created or destroyed.     * Atoms in an element are all identical.     * In compounds, each atom of an element is always joined to a fixed number of atoms of other elements.     * During chemical reactions, atoms rearrange to make new substances.

• Conservation of Mass: No atoms are lost or gained, so the mass of the reactants is equal to the mass of the products.

• Signs of a Chemical Reaction:     * Colour change.     * Temperature change.     * Gas given off.     * Solid formed.

• Oxides and Element Properties:     * Elements are described by symbols ($1$ or $2$ letters). The first letter is always a CAPITAL and the second is LOWER CASE (e.g., Nitrogen is $N$, Iron is $Fe$).     * Elements burn in air/oxygen to form oxides:         * $calcium + oxygen \rightarrow calcium\,oxide$ (Metal oxide, tends to form alkaline solutions).         * $carbon + oxygen \rightarrow carbon\,dioxide$ (Non-metal oxide, tends to form acidic solutions).

• Evolution of the Periodic Table:     * Dobereiner: Arranged elements in Triads based on similar chemical reactivity.     * Newlands: Law of octaves based on increasing mass.     * Mendeleev: Arranged by increasing atomic mass and grouped by similar properties; notably left GAPS for undiscovered elements.

Energy Transfers (Year 8)

• Key Scientific Words and Definitions:     * Internal energy: Also called thermal energy. The energy stored in the movement of particles.     * Evaporation: When part of a liquid evaporates, the fastest-moving particles escape to form a gas ($Note$: Transcript also maps this to catalyst definition erroneously under the list).     * Radiation: The way energy is transferred through empty space and transparent materials; involves infrared waves.     * Conduction: Energy transfer through solids by heating.     * Convection: Energy transfer by heating in fluids (liquids and gases).     * Emit: To give out.     * Absorbed: Taken into an object.     * Reflected: To bounce off a surface.     * Medium: Any substance through which something travels.     * Fluid: A gas or a liquid.     * Efficiency: A measure of how much energy something wastes.     * Payback time: Time taken to recover costs of energy-saving measures via savings.

• Energy and Temperature:     * Temperature is measured in degrees Celsius ($^{\circ}C$).     * Interal energy is measured in joules ($J$).     * Thermal energy storage depends on: temperature, material, and mass.     * Power: Amount of Energy in $J$ transferred per second. Measured in watts ($W$) or kilowatts ($kW$).     * $1\,kilowatt\text{-}hour\,(kWh)$ is energy transferred in $1$ hour by a $1\,kW$ appliance.     * Energy cannot be created or destroyed.

• Mechanisms of Heat Transfer:     * Conduction: Best in solids where particles are held tightly. Vibrations are passed on. Metals are best; wood, glass, and plastic are insulators. Gases hardly conduct because particles are far apart.     * Convection: Occurs in fluids. Heated particles spread apart, fluid becomes less dense and rises, replacement by cool fluid creates a convection current.     * Radiation: Does not require particles. Hot objects emit it; it can be focused, reflected, or absorbed. Dark/dull surfaces are good absorbers; shiny surfaces are good reflectors.

• Vacuum Flask Insulation:     * Conduction reduced by vacuum, stopper, glass, cork, and air spaces.     * Convection reduced by vacuum, stopper, and trapped air spaces.     * Radiation reduced by silvered glass walls.

Breathing and Respiration (Year 8)

• Key Scientific Words and Definitions:     * Respiration: An exothermic reaction releasing energy from glucose.     * Aerobic respiration: Respiration using oxygen.     * Anaerobic respiration: Respiration without oxygen.     * Trachea: Air passage connecting nasal cavity to bronchus. Contains cilia and mucus to trap dirt.     * Diaphragm: Muscle that contracts/moves down to increase chest volume.     * Alveoli: Sacks where gas exchange occurs.     * Breathing: Intercostal muscles and diaphragm changing to adjust lung size.

• Gas Exchange and Lung Anatomy:     * Lung components: Trachea, ribs, intercostal muscles, diaphragm, bronchus, bronchiole, alveoli.     * Adaptation: Millions of alveoli provide a large surface area for fast diffusion of oxygen in and carbon dioxide out.

• Respiratory Equations:     * Aerobic: $OXYGEN + GLUCOSE \rightarrow CARBON\,DIOXIDE + WATER$ (Occurs in mitochondria).     * Anaerobic (Animals): $GLUCOSE \rightarrow LACTIC\,ACID$ (Occurs in cytoplasm, less efficient).

• Smoking Risks:     * Nicotine: Narrows arteries, causes heart disease.     * Tar: Causes cancer, coats lungs, breaks alveoli (emphysema).     * Carbon monoxide: Reduces oxygen capacity of red blood cells.     * High temperatures: Stops cilia from cleaning mucus.

Metals and Their Uses (Year 8)

• Key Scientific Words and Definitions:     * Catalyst: Speeds up reactions without being used up. Found in catalytic converters.     * Corrosion: Reaction of metals with chemicals in air/water. Metal oxides form.     * Rusting: Specific corrosion of iron or steel. Requires water and oxygen.     * Alloy: A metal mixed with other elements to improve properties (e.g., harder, resistant to corrosion).     * Effervescence: Gas production in a liquid reaction.

• Properties and Specific Metals:     * Metals: Shiny, high melting point, flexible/malleable, good conductors.     * Non-metals: Dull, low melting point, brittle, poor conductors.     * Copper: Electrical circuits (conductive), water pipes (malleable, unreactive).     * Aluminium: Window frames and airplane parts (strong, light).     * Gold: Jewellery (malleable, stays shiny).     * Iron: Construction (strong, cheap).

• Reactivity and Protection:     * Protection methods: Paint, oil, plastic, powder coating, galvanisation (sacrificial protection).     * Hydrogen Test: A lit splint burns with a "squeaky pop".     * Formulas:         * $Metal + Oxygen \rightarrow Metal\,Oxide$         * $Metal + Water \rightarrow Metal\,hydroxide + Hydrogen$         * $Metal + Acid \rightarrow Salt + Hydrogen$

• Famous Alloys:     * Solder: $Pb + Sn$ (low melting point).     * Stainless Steel: $Fe + C + Cr + Ni$ (stronger, rust-resistant).     * Duralumin: $Al + Cu + Mg$ (light and strong).

Fluids (Year 8)

• Key Scientific Words and Definitions:     * Brownian motion: Erratic movement of small specks of matter caused by collisions with fluid particles.     * Density: Mass per unit volume ($g/cm^3$ or $kg/m^3$). Formula: $\text{Density} = \frac{\text{mass}}{\text{volume}}$.     * Upthrust: Force pushing upward in a fluid.     * Weight: Force of gravity in Newtons ($N$).     * Streamlined: Smooth shape to reduce drag.

• Pressure in Fluids:     * Acts in all directions due to particle collisions.     * Increases with depth (more fluid weight above).     * Decreases with altitude (less air above).     * Ways to increase gas pressure: Add more particles, heat the gas, reduce container volume.

• Floating and Sinking:     * If density of object < density of fluid ($1\,g/cm^3$ for water), it floats.     * Anomalous behavior of water: Ice expands and is less dense than liquid water, so it floats on ponds.

Unicellular Organisms (Year 8)

• Key Scientific Words and Definitions:     * Prokaryotes: Unicellular with no nuclei (e.g., bacteria).     * Protoctists: Unicellular organisms; some photosynthesise (producers).     * Microscopic Fungi (Yeast): Reproduce by budding.         * Fermentation: $glucose \rightarrow carbon\,dioxide + ethanol$.     * Movement: Pseudopods (extensions), cilia (hairs), flagella (tails).     * Growth factors: Warmth, food, moisture, oxygen (for aerobic).     * Limiting factor: Stops population growth.

• Food Chains and Decomposition:     * Decomposers release enzymes to break down insoluble molecules.     * Arrows show energy transfer.     * Pyramid of numbers: Fewer animals at higher levels due to energy loss.

Combustion (Year 8)

• Key Scientific Words and Definitions:     * Hydrocarbons: Compounds of hydrogen and carbon only.     * Exothermic: Gives out energy/heat.     * Phlogiston: Disproven theory regarding why things burn.     * Fire Triangle: Heat, Oxygen, Fuel.

• Combustion Types:     * Complete: $Hydrocarbon + oxygen \rightarrow carbon\,dioxide + water$.     * Incomplete: $Hydrocarbon + oxygen \rightarrow carbon\,dioxide + carbon\,monoxide + carbon\,(soot) + water$.

• Tests:     * Carbon Dioxide: Bubble through limewater (turns cloudy).     * Water: Blue cobalt chloride paper turns pink.

Earth and Space (Year 8)

• Key Scientific Words and Definitions:     * Weight: Force of gravity ($N$). Changes with location.     * Mass: Amount of matter ($kg$). Constant regardless of location.     * Gravity: $\text{weight}\,(N) = \text{mass}\,(kg) \times \text{gravitational\,field\,strength}\,(N/kg)$.     * Galaxy: Millions of stars grouped.

• Solar System Models:     * Ptolemy: Geocentric (Earth center).     * Copernicus: Heliocentric (Sun center).     * Galileo: Provided evidence using first telescopes.

• Cycles:     * Day/Night: Earth spins on axis ($24$ hours).     * Year: Earth orbits sun ($365.25$ days).     * Seasons: Caused by Earth's tilt.

Rocks (Year 8)

• Key Scientific Words and Definitions:     * Mineral: Naturally occurring element/compound forming grains.     * Interlocking: Crystals with no gaps.     * Porous: Tiny gaps (porosity).     * Permeable: Lets water soak through.     * Weathering/Erosion: Physical/biological breakdown and movement of rock.

• Rock Types:     * Igneous: Fast cooling (small crystals - e.g., obsidian); Slow cooling (large crystals - e.g., granite).     * Metamorphic: High pressure/temp (e.g., Slate to Schist to Gneiss).     * Sedimentary: Deposited layers (e.g., Sandstone, Limestone).