JCE General Science (Syllabus 43) flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Independent variable
- The factor deliberately changed in an investigation; all other factors are kept constant so its effect on the dependent variable can be measured.
- Dependent variable
- The factor measured or observed in an experiment; it is expected to respond to changes in the independent variable.
- Control variable
- A factor kept the same across all trials so it cannot explain differences in the dependent variable.
- Accuracy vs precision
- Accuracy is closeness to the true value; precision is closeness of repeated measurements to each other, regardless of closeness to the true value.
- Percentage error formula
- Percentage error equals the absolute difference between measured and accepted values, divided by the accepted value, multiplied by 100.
- SI base units
- The seven SI base units include metre for length, kilogram for mass, second for time, kelvin for temperature, and mole for amount of substance.
- Cell membrane
- A selectively permeable barrier around a cell that controls which substances enter and leave, maintaining internal conditions.
- Photosynthesis equation
- Carbon dioxide plus water, using light energy and chlorophyll, produces glucose and oxygen; the balanced equation is 6CO2 + 6H2O -> C6H12O6 + 6O2.
- Aerobic respiration
- Glucose reacts with oxygen to release energy, producing carbon dioxide and water; word equation: glucose + oxygen -> carbon dioxide + water.
- Osmosis
- The diffusion of water molecules across a partially permeable membrane from a region of higher water concentration to lower water concentration.
- Enzyme
- A biological catalyst made of protein that speeds up a specific reaction without being used up; high temperature or wrong pH can denature it.
- Food test for starch
- Add iodine solution to the sample; a blue-black colour indicates starch, while a yellow-brown colour indicates starch is absent.
- Dominant allele
- An allele that is expressed in the phenotype even when only one copy is present; a recessive allele is expressed only with two copies.
- Atomic number
- The number of protons in an atom's nucleus; it identifies the element and equals the number of electrons in a neutral atom.
- Mass number
- The total number of protons and neutrons in an atom's nucleus; electrons are ignored because their mass is negligible.
- Conservation of mass
- In a closed system, the total mass of reactants equals the total mass of products because atoms are rearranged, not created or destroyed.
- pH scale
- A scale from 0 to 14: values below 7 are acidic, 7 is neutral, and values above 7 are alkaline; each unit represents a tenfold change in hydrogen ion concentration.
- Neutralisation reaction
- An acid reacts with a base to form a salt and water; the reaction reduces acidity and produces a solution closer to neutral.
- Filtration
- A separation method that uses a filter to trap insoluble solid particles while allowing a liquid or solution to pass through.
- Chemical change
- A change that produces new substances with different properties; common signs include gas release, colour change, precipitate, or energy change.
- Speed formula
- Speed equals distance travelled divided by time taken; average speed uses total distance divided by total time.
- Acceleration formula
- Acceleration equals change in velocity divided by the time taken; it is measured in metres per second squared.
- Balanced forces
- Forces equal in size and opposite in direction produce zero resultant force, so an object remains at rest or moves at constant velocity.
- Weight formula
- Weight equals mass multiplied by gravitational field strength; mass is measured in kilograms and weight in newtons.
- Ohm's law
- For a conductor at constant temperature, voltage equals current multiplied by resistance; V = IR, with V in volts, I in amperes, and R in ohms.
- Wave equation
- Wave speed equals frequency multiplied by wavelength; frequency is in hertz and wavelength in metres.
- Rock cycle
- A continuous set of processes that change rock among igneous, sedimentary, and metamorphic types through melting, cooling, weathering, deposition, and heat or pressure.
- Water cycle
- The continuous movement of water through evaporation, condensation, precipitation, and collection or runoff, driven mainly by solar energy and gravity.
- Greenhouse effect
- Atmospheric gases absorb and re-emit infrared radiation from Earth's surface, warming the lower atmosphere; the effect is enhanced by human-produced carbon dioxide and methane.
- Renewable resource
- A natural resource that is replenished faster than it is used, such as sunlight, wind, flowing water, and sustainably managed biomass.
- Weather versus climate
- Weather is short-term atmospheric conditions in a place; climate is the average pattern of weather over many years.
- Tectonic plates
- Large moving sections of Earth's lithosphere; their interactions at boundaries cause earthquakes, volcanic activity, and mountain formation.