Science
Core concepts
Science questions cover scientific inquiry, life science, physical science, and Earth/space science. Inquiry requires distinguishing observation (using senses or instruments) from inference (an interpretation), a hypothesis (a testable prediction) from a theory (a well-supported explanation), and independent from dependent variables. Life science includes cells, photosynthesis and respiration, food webs, ecosystems, adaptation, and heredity. Physical science includes states of matter, physical versus chemical change, forces and motion, energy transfer, electricity and magnetism, and waves. Earth/space science includes the rock cycle, weathering and erosion, plate tectonics, the water cycle, weather versus climate, and the causes of seasons.
Traps
A controlled experiment changes one independent variable and holds others constant. Mass is the amount of matter; weight depends on gravity. Weathering breaks rock in place; erosion transports the pieces. Rotation causes day and night; revolution plus axial tilt causes seasons-not distance from the Sun. Physical changes do not create new substances; chemical changes do. Energy flows through food webs while matter cycles.
Worked example
Students test whether fertilizer affects plant height. Fertilizer amount is the independent variable; plant height is the dependent variable; light, water, soil, and pot size are controlled variables. Rule of thumb: the independent variable is what the experimenter changes; the dependent variable is what is measured.