NCEA L1 Science flashcards
NCEA L1 Science · Build recall with a focused review session.
36 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Electric current
- The rate at which electric charge flows past a point, measured in amperes. One ampere equals one coulomb of charge per second, calculated as I = Q/t.
- Potential difference (voltage)
- The energy transferred per unit of charge between two points in a circuit, measured in volts. One volt equals one joule per coulomb, calculated as V = E/Q.
- Ohm's law
- For an ohmic conductor at constant temperature, current is directly proportional to voltage, giving V = IR, where resistance R is measured in ohms.
- Electrical power
- The rate at which electrical energy is transferred, given by P = VI and, using Ohm's law, also P = I²R or P = V²/R, measured in watts.
- Series and parallel circuits
- In series, current is identical everywhere and voltages add. In parallel, voltage is identical across branches and branch currents add.
- Electromagnetic induction
- A changing magnetic flux through a coil induces a voltage across it. Generators use this to convert kinetic energy into electrical energy without direct contact.
- Wave equation
- Wave speed equals frequency multiplied by wavelength (v = fλ). Frequency is fixed by the source, so wavelength changes when wave speed changes between media.
- Refraction
- The change in direction of a wave as its speed changes on entering a different medium. Light bending towards the normal shows it has slowed down.
- Total internal reflection
- Occurs when light in a denser medium strikes a boundary beyond the critical angle and reflects entirely back inside, allowing optical fibres to carry signals.
- Electromagnetic spectrum order
- From longest to shortest wavelength: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. All travel at the speed of light in a vacuum.
- Resonance
- A large-amplitude vibration produced when a driving frequency matches an object's natural frequency, important in musical instruments and in structural vibration problems.
- Sound transmission
- Sound is a longitudinal wave needing a medium of vibrating particles. It travels about 340 m/s in air and cannot pass through a vacuum.
- Speed, velocity and acceleration
- Speed is distance divided by time. Velocity includes direction. Acceleration is the change in velocity divided by the time taken, measured in m/s².
- Velocity-time graph
- On a velocity-time graph the gradient gives acceleration and the area under the line gives displacement, allowing motion to be analysed from a single graph.
- Newton's second law
- The net force on an object equals its mass multiplied by its acceleration (F = ma). Acceleration is in the direction of the net force.
- Weight versus mass
- Mass is the amount of matter in kilograms and is unchanged by location. Weight is the gravitational force W = mg, measured in newtons.
- Work and power
- Work is force multiplied by distance moved in the force's direction (W = Fd), in joules. Power is work done per second (P = W/t), in watts.
- Conservation of mechanical energy
- Without friction, the sum of kinetic energy (½mv²) and gravitational potential energy (mgh) stays constant as an object moves.
- Pressure in fluids
- Pressure is force per unit area, measured in pascals. In a fluid at rest, pressure increases with depth, which is why dam walls are thicker at the base.
- Balancing chemical equations
- Atoms are conserved in reactions, so coefficients are adjusted until each element has equal numbers of atoms on both sides. Subscripts must never be altered.
- Acids and bases
- Acids release hydrogen ions in solution and have pH below 7. Bases release hydroxide ions or accept hydrogen ions and have pH above 7. pH 7 is neutral.
- Neutralisation
- An acid reacting with a base produces a salt and water. Acid plus metal carbonate instead gives a salt, water and carbon dioxide gas.
- Displacement reaction
- A more reactive metal takes the place of a less reactive metal in its salt solution, for example zinc displacing copper from copper sulfate solution.
- Rates of reaction
- Reaction rate increases with higher temperature, higher concentration, greater surface area and catalysts. A catalyst lowers activation energy without being consumed.
- Exothermic and endothermic
- Exothermic reactions transfer energy to the surroundings, raising their temperature. Endothermic reactions absorb energy, lowering the temperature of the surroundings.
- Rusting conditions
- Iron rusts only when both oxygen and water are present. Painting, greasing or galvanising excludes them, and zinc also protects iron sacrificially.
- Earth's layered structure
- Earth consists of a thin crust, a solid but slowly flowing mantle, a liquid outer core and a solid inner core. Mantle convection drives plate movement.
- Plate boundaries
- Divergent boundaries form new crust as plates separate, convergent boundaries involve subduction or collision, and transform boundaries involve plates sliding past each other.
- Earthquake focus and epicentre
- The focus is the point underground where rock breaks and seismic energy is released. The epicentre is the point on the surface directly above it.
- P waves and S waves
- P waves are longitudinal and fastest, travelling through solids and liquids. S waves are transverse, slower, and cannot pass through liquids, revealing the liquid outer core.
- The rock cycle
- Igneous rock forms from cooled magma, sedimentary rock from compacted deposits, and metamorphic rock from heat and pressure. Any type can transform into another.
- Earth's rotation and revolution
- Earth spins once on its axis every 24 hours, causing day and night, and orbits the Sun every 365.25 days, which is why leap years are needed.
- Cause of the seasons
- Earth's axis is tilted about 23.5°, so each hemisphere receives sunlight at a different angle and for different durations through the year, producing seasons.
- Phases of the Moon
- The Moon's changing appearance results from the changing angle between the Sun, Earth and Moon as the Moon orbits Earth roughly every 29.5 days.
- Eclipses
- A solar eclipse occurs at new Moon when the Moon blocks the Sun. A lunar eclipse occurs at full Moon when Earth's shadow falls on the Moon.
- Tides
- The Moon's gravity raises two tidal bulges, giving two high tides daily. Spring tides occur at new and full Moon; neap tides at quarter phases.