sci

Independent variable

"The one variable you deliberately change in an experiment (e.g. the type of water in Sally's boiling test)."

Dependent variable

"The variable you measure as a result (e.g. the time taken for the water to boil)."

Controlled variables

"Variables kept the same to make it a fair test (e.g. volume of water

Producer

"An organism that makes its own food by photosynthesis

Primary consumer

"A herbivore that eats producers

Secondary consumer

"An animal that eats primary consumers (eats the herbivores)."

Carnivore

"An animal that eats other animals

Community (ecology)

"All the living organisms (all the populations of all species) living together in an ecosystem."

Population

"All the organisms of ONE species in an area

Photosynthesis

"Process where producers use sunlight to convert CO2 + water into glucose + oxygen. Removes CO2 from the atmosphere in the carbon cycle."

Respiration (carbon cycle)

"Process that releases CO2 back into the atmosphere from living organisms."

Combustion

"Burning of fuels (including fossil fuels) that releases CO2 into the atmosphere."

Energy transfer between trophic levels

"Only about 10% of energy passes to the next level in a food chain."

Why only 10% of energy is passed on

"Energy is lost as heat from respiration

Pyramid of biomass

"A pyramid showing mass of organisms at each level — widest at the producer (bottom)

Abiotic factor

"A non-living factor that affects a food chain

Eutrophication

"Process where excess nutrients (from fertiliser runoff) cause algal blooms

Farming cause of algal blooms

"Overuse of fertilisers — nitrates and phosphates wash (run off) into streams and lakes."

Ribosomes

"Cell structures that make proteins."

Mitochondria

"Site of aerobic respiration in a cell — release energy. Many are found in cells that need lots of energy (e.g. root hair cells)."

Nucleus

"Controls the cell and contains the genetic material (DNA)."

Diffusion

"The net movement of particles from a high concentration to a low concentration (down the concentration gradient). No energy needed."

Osmosis

"The net movement of water molecules from a high water concentration (dilute) to a low water concentration (concentrated) across a partially permeable membrane."

Active transport

"The net movement of particles from a low to a high concentration (against the gradient)

Root hair cell adaptations

"Long thin projection for a large surface area

Why root hair cells use active transport

"Mineral ions are at a higher concentration inside the cell than in the soil

Potato in pure water (tube A)

"Water moves INTO the cells by osmosis

Potato with no change (tube B)

"The sugar solution had the SAME concentration as the inside of the potato cells (isotonic)

Red blood cell in pure water

"Water enters by osmosis; the cell swells and bursts (lyses) because it has no cell wall."

Glucose absorbed when intestine has less than blood

"By active transport (moved against the concentration gradient using energy)."

Sugar into a cell when more is outside

"By diffusion (moves down the concentration gradient)."

Right atrium

"The chamber where deoxygenated blood returns to the heart from the body."

Pulmonary vein

"The blood vessel that carries oxygenated blood (highest oxygen) from the lungs INTO the heart (to the left atrium)."

Pulmonary artery

"Carries deoxygenated blood from the right ventricle to the lungs."

Order of blood to the lungs

"Right atrium → right ventricle → pulmonary artery → lungs."

Heart valves

"Flaps that stop the backflow of blood

Aerobic respiration

"Glucose + Oxygen → Carbon dioxide + Water + Energy."

Anaerobic respiration in muscles

"Happens when there is not enough oxygen; glucose → lactic acid (+ a little energy)."

Gas exchange site

"Takes place in the alveoli (tiny air sacs) in the lungs."

Trachea

"The windpipe — carries air to the lungs."

Bronchi

"Tubes branching from the trachea into each lung."

Where most food is absorbed

"In the small intestine."

Villus capillary

"The small blood vessel (capillary) in a villus that absorbs digested food molecules."

Oxidising agent symbol

"A flame over a circle (O) — means the substance supplies oxygen and helps other things burn."

Flammable symbol

"A single flame — the substance catches fire easily."

Atomic (mass) number

"The number of protons + neutrons in an atom."

Atomic number

"The number of protons in an atom."

Aluminium ion configuration

"Al is 2

Metal + acid reaction

"Metal + acid → salt + hydrogen. e.g. magnesium + nitric acid → magnesium nitrate + hydrogen."

Acid + base (alkali) reaction

"Acid + base → salt + water. This is neutralisation."

Acid + carbonate reaction

"Acid + carbonate → salt + water + carbon dioxide."

Neutralisation

"A reaction between an acid and a base/alkali producing a salt and water

Exothermic reaction

"A reaction that releases energy to the surroundings (temperature rises)."

Endothermic reaction

"A reaction that takes in energy from the surroundings (temperature falls). Decomposition of lithium carbonate is endothermic."

Temperature (particle definition)

"A measure of the average kinetic energy (average speed) of the particles in a substance."

pH scale

"Below 7 = acid

Strong base vs weak acid pH

"pH 13 = strong base

Red litmus in acid

"Stays red (red litmus only turns blue in a base/alkali)."

Blue litmus in acid

"Turns red."

Solubility of gases and pressure

"As pressure increases

Solubility of gases and temperature

"As temperature increases

Saturated solution

"A solution that can no longer dissolve any more solute at that temperature."

Test for oxygen

"A glowing wooden splint relights."

Test for hydrogen

"A lit splint gives a squeaky pop."

Test for carbon dioxide

"Bubbled through limewater

Limewater going cloudy

"A precipitate of calcium carbonate forms

Ionic bonding

"Bonding between a metal and a non-metal where electrons are transferred to form ions

Molecule

"A particle of two or more atoms joined by covalent bonds

Covalent bond

"A shared pair of electrons between two non-metal atoms."

Electrons used per single bond

"One carbon atom uses 1 electron to form 1 single covalent bond."

Fluorine molecule (F2) bonding

"A single covalent bond — the two F atoms share one pair of electrons; each F also has 3 lone (unbonded) pairs."

Balancing sodium + oxygen

"4Na + O2 → 2Na2O."

Reactivity series (order)

"K

Displacement rule

"A more reactive metal displaces a less reactive metal from its compound (solution)."

Zinc / Copper / Magnesium with sulfates

"Mg displaces both Zn and Cu; Zn displaces only Cu; Cu displaces neither. A metal does not react with its own sulfate."

Acid to make ammonium nitrate

"Nitric acid (ammonia + nitric acid → ammonium nitrate)."

Ammonia solution type

"It is alkaline — a base (an alkali)."

Lead nitrate + potassium iodide

"→ lead iodide + potassium nitrate. A bright yellow solid (lead iodide) forms."

Precipitation reaction

"Two soluble solutions react to form an insoluble solid (a precipitate)."

Solubility of the lead iodide products

"Pb(NO3)2 = soluble (aq)

Ingredient that lowers Cola pH

"Phosphoric acid."

Ion that makes a solution acidic

"The hydrogen ion (H+)."

How to neutralise an acid like Cola

"Add a base/alkali (e.g. sodium hydroxide or an antacid) to raise the pH towards 7."

Decomposition of lithium carbonate

"Li2CO3 (s) → Li2O (s) + CO2 (g). The missing product is carbon dioxide gas."

Pressure formula

"Pressure = Force ÷ Area (P = F/A). Unit: pascals (Pa) or N/m2."

Why high heels hurt more

"They put the same weight force through a much smaller area

Distance-time graph: flat line

"The object is stationary (not moving)."

Distance-time graph: straight slope

"The object moves at a constant speed. A steeper slope = faster."

Distance-time graph: line returning to zero

"The object is travelling back towards the start (e.g. returning home)."

Newton's First Law

"An object stays still

Speed formula

"Speed = distance ÷ time (v = d/t)."

Acceleration formula

"Acceleration = change in velocity ÷ time (a = Δv/t). Unit: m/s2."

Velocity-time graph: sloped line

"The object is accelerating."

Velocity-time graph: flat line

"The object is moving at a constant velocity."

Series circuit

"One single loop. The current is the same at every point; voltage is shared between components."

Parallel circuit

"Has branches. The current splits between branches; each branch gets the full supply voltage."

Current in a series circuit

"The same through every component (e.g. equal through both bulbs)."

Ammeter

"Measures current (in amps). Always connected in series."

Voltmeter

"Measures potential difference (in volts). Always connected in parallel across a component."