MATSEC SEC Core Science flashcards
MATSEC SEC Core Science · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- SI unit of force
- The newton (N) is the SI unit of force; one newton is the force that gives a one-kilogram mass an acceleration of one metre per second squared (F = m × a).
- Difference between mass and weight
- Mass is the amount of matter in an object, measured in kilograms and unchanged by location; weight is the force of gravity on that mass, measured in newtons, so it changes on other planets.
- Formula for speed
- Speed equals distance travelled divided by time taken, usually in metres per second. Average speed uses total distance over total time, even when the speed varies during the journey.
- Newton's first law
- An object remains at rest or moves at constant velocity in a straight line unless a resultant external force acts on it. This is also called the law of inertia.
- Newton's third law
- For every action force there is an equal and opposite reaction force, acting on a different object. For example, a rocket pushes gas backwards and the gas pushes the rocket forwards.
- Formula for kinetic energy
- Kinetic energy equals one half times mass times velocity squared (KE = ½mv²), measured in joules. Doubling the speed quadruples the kinetic energy of a moving object.
- Conservation of energy
- Energy cannot be created or destroyed, only transferred between stores or transformed from one form to another. The total energy in a closed system stays constant.
- Formula for density
- Density equals mass divided by volume, usually in grams per cubic centimetre or kilograms per cubic metre. It explains why a dense object such as iron sinks in water.
- Ohm's law
- Voltage equals current multiplied by resistance (V = I × R) for a conductor at constant temperature. Resistance is measured in ohms and current in amperes.
- Series versus parallel circuits
- In series, current is the same everywhere and voltage divides between components. In parallel, voltage is the same across each branch and current splits between branches.
- Electrical power formula
- Power equals voltage multiplied by current (P = V × I), measured in watts. Energy used equals power multiplied by time, often billed in kilowatt-hours.
- Difference between AC and DC
- Direct current flows in one direction only, as from a battery. Alternating current repeatedly reverses direction, as from the mains supply at about 50 hertz in Europe.
- Properties of a transverse wave
- In a transverse wave the oscillations are perpendicular to the direction of travel, as in light and water waves; amplitude is maximum displacement and wavelength is the distance between successive crests.
- Wave speed equation
- Wave speed equals frequency multiplied by wavelength (v = f × λ). Frequency is measured in hertz, wavelength in metres, and speed in metres per second.
- Law of reflection
- The angle of incidence equals the angle of reflection, both measured from the normal, an imaginary line perpendicular to the mirror surface at the point of reflection.
- Refraction of light
- Light bends when it passes between media of different optical density, changing speed. Entering a denser medium such as glass, it slows and bends towards the normal.
- Speed of light in vacuum
- Light travels at approximately 3 × 10⁸ metres per second in a vacuum, the fastest possible speed. It slows in denser media such as water or glass.
- Difference between heat and temperature
- Temperature measures the average kinetic energy of particles, in kelvin or degrees Celsius. Heat is the thermal energy transferred from a hotter body to a cooler one.
- Three methods of heat transfer
- Conduction transfers heat through solids by particle vibration; convection transfers heat through fluids by moving currents; radiation transfers heat by infrared electromagnetic waves needing no medium.
- Balancing a chemical equation
- Adjust coefficients, never subscripts, so the number of atoms of each element is identical on both sides. This reflects conservation of mass during a chemical reaction.
- Relative formula mass
- The sum of the relative atomic masses of all atoms in a chemical formula, for example water H₂O has a relative formula mass of 1 + 1 + 16 = 18.
- The mole concept
- One mole of any substance contains 6.02 × 10²³ particles, Avogadro's number. The mass of one mole in grams equals the relative formula mass of the substance.
- pH scale and indicators
- The pH scale runs from 0 to 14: below 7 is acidic, 7 is neutral, above 7 is alkaline. Universal indicator shows colour changes; litmus turns red in acid and blue in alkali.
- Neutralisation reaction
- An acid reacts with a base to form a salt and water only. For example, hydrochloric acid plus sodium hydroxide gives sodium chloride plus water, releasing heat.
- Acid plus metal reaction
- An acid reacting with a reactive metal produces a salt and hydrogen gas, which gives a squeaky pop with a lit splint. Copper does not react with dilute acids.
- Acid plus carbonate reaction
- An acid reacting with a carbonate produces a salt, water and carbon dioxide gas. The carbon dioxide turns limewater milky, a standard test for the gas.
- Difference between elements and compounds
- An element contains only one kind of atom and cannot be split chemically. A compound contains two or more elements chemically combined in fixed proportions, with properties unlike the elements.
- Structure of an atom
- An atom has a nucleus of protons and neutrons, surrounded by electrons in shells. Protons are positive, neutrons neutral, electrons negative; atoms are electrically neutral overall.
- Plant versus animal cells
- Plant cells have a cellulose cell wall, chloroplasts for photosynthesis and a permanent vacuole. Animal cells lack these but both share a nucleus, cytoplasm, membrane and mitochondria.
- Word equation for photosynthesis
- Carbon dioxide plus water, using light energy absorbed by chlorophyll, produces glucose and oxygen. It occurs in chloroplasts and is the reverse of aerobic respiration.
- Aerobic versus anaerobic respiration
- Aerobic respiration uses oxygen to release energy from glucose, producing carbon dioxide and water. Anaerobic respiration occurs without oxygen, producing lactic acid in muscles or ethanol in yeast.
- Energy transfer in food chains
- Only about ten percent of energy passes to the next trophic level; the rest is lost through respiration, heat, movement and undigested waste. Producers form the base of every food chain.