Grade 12 · Science review
Biology, chemistry, and physics questions from US classrooms. Written in American English for students, parents, and teachers in the United States.
Open a card to see the answer. These are original practice items for US elementary students — not a state test copy.
Answer: photosynthesis, respiration, and fossil-fuel burning
CO₂ is a key greenhouse gas.
Answer: variety of life in an ecosystem
More diversity often means more resilience.
Answer: stores more carbon than it releases, like a healthy forest
Oceans and forests can act as sinks.
Answer: excess fertilizer runoff that overfeeds algae
Algal blooms can steal oxygen when they decay.
Answer: spreads in a new habitat and can harm natives
Zebra mussels in the Great Lakes are a US example.
Answer: wind, solar, and hydro
They replenish on a human timescale.
Answer: blocks much harmful UV from the Sun
Stratospheric ozone is helpful; ground-level ozone is a pollutant.
Answer: has an outsized effect on its ecosystem
Sea otters and wolves are textbook cases.
Answer: how many cycles occur per second (hertz)
f = 1/T.
Answer: wave speed equals frequency times wavelength
In air, sound is much slower than light.
Answer: the same through each resistor
Voltage drops add to the battery voltage.
Answer: the same as the source (ideal wires)
Currents in the branches add.
Answer: V = IR
Voltage, current, resistance.
Answer: mass times velocity (p = mv)
It is conserved in a closed system with no external impulse.
Answer: perpendicular to the direction of travel
Light and string waves are transverse.
Answer: longitudinal mechanical wave
It needs a medium; light does not.
Pick the next article in this topic — that is how a magazine issue is meant to be used.
