JC Science flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Hypothesis
- A testable, falsifiable prediction about the relationship between variables, stated before an investigation begins and evaluated against the evidence collected.
- Control group
- The group in an experiment that receives no treatment or a placebo, providing a baseline for comparison with the experimental group.
- Validity
- The extent to which a method measures what it claims to measure, achieved by controlling variables so only the independent variable affects the result.
- Osmosis
- The diffusion of water across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration, requiring no energy.
- Enzyme active site
- The specific region of an enzyme where the substrate binds, complementary in shape to that substrate, so each enzyme catalyses only particular reactions.
- Aerobic respiration equation
- Glucose plus oxygen produces carbon dioxide plus water, releasing energy; it occurs mainly in mitochondria and is the body's main energy source.
- Dominant allele
- An allele whose trait appears in the phenotype whenever it is present, even if only one copy is inherited alongside a recessive allele.
- Meiosis
- Cell division producing four genetically different haploid gametes, halving the chromosome number so fertilisation restores the diploid number.
- Natural selection
- The process where inherited variation means some individuals survive and reproduce more successfully, so advantageous alleles become more common over generations.
- Trophic level
- A feeding position in a food chain, such as producer or primary consumer, with roughly ten percent of energy passing to the next level.
- Biodiversity
- The variety of species and genetic variation within an ecosystem; higher biodiversity generally makes the ecosystem more stable and resilient to change.
- Eutrophication
- Nutrient enrichment of water by fertiliser run-off, causing algal growth, then oxygen depletion when algae decay, killing fish and other organisms.
- Chromatography Rf value
- The distance travelled by the spot divided by the distance travelled by the solvent front, used to identify dissolved substances in a mixture.
- Compound
- A substance formed when two or more elements are chemically combined in fixed proportions, with properties different from the elements that formed it.
- Isotopes
- Atoms of the same element with the same number of protons but different numbers of neutrons, giving different mass numbers but identical chemical properties.
- Neutralisation
- The reaction of an acid with a base to form a salt and water, for example hydrochloric acid plus sodium hydroxide gives sodium chloride and water.
- Activation energy
- The minimum energy particles must have when they collide for a reaction to occur; catalysts lower it without being used up.
- Exothermic reaction
- A reaction that transfers energy to the surroundings, usually raising the temperature, and has a negative enthalpy change.
- Resultant force
- The single force equivalent to all the forces acting on an object combined; it determines the direction and size of any acceleration.
- Kinetic energy formula
- Kinetic energy equals half the mass multiplied by the velocity squared (KE = ½mv²), measured in joules when mass is in kilograms.
- Power
- The rate at which work is done or energy is transferred, calculated as work done divided by time and measured in watts.
- Ohm's law
- The voltage across a conductor equals the current through it multiplied by its resistance (V = IR), provided temperature stays constant.
- Wave equation
- Wave speed equals frequency multiplied by wavelength (v = fλ), with speed in metres per second, frequency in hertz and wavelength in metres.
- Refraction
- The bending of light as it passes between media of different density, changing speed; it bends towards the normal entering a denser medium.
- Igneous rock
- Rock formed when molten magma or lava cools and solidifies; slow cooling underground produces large crystals, rapid cooling at the surface produces small crystals.
- Climate versus weather
- Weather is short-term atmospheric conditions such as today's rain, while climate is the long-term average pattern usually assessed over about thirty years.
- Redshift
- The stretching of light from distant galaxies towards longer wavelengths, evidence that the universe is expanding according to the Big Bang model.
- Informed consent
- Agreement to take part in research given after understanding the purpose, procedures, risks and the right to withdraw at any time.
- Sustainability
- Meeting present needs without compromising the ability of future generations to meet theirs, balancing environmental, social and economic factors.
- Renewable energy
- Energy from sources naturally replenished on a human timescale, such as solar, wind, hydro, geothermal and biomass, unlike finite fossil fuels.
- Peer review
- Independent expert scrutiny of scientific work before publication, checking methods, evidence and conclusions for quality and to reduce errors or bias.
- Quadrats
- Square frames placed randomly to sample organisms in an area; the mean count per quadrat is scaled up to estimate population size.