General Science

air is generally less dense than liquid water because …

air molecules are farther apart

which gas makes up the largest share of Earth’s atmosphere?

nitrogen

which subatomic particle has a negative charge?

electron

liquid water changing to water vapor is called…

evaporation

how does most energy from the Sun travel through the vacuum of space?

radiation

warm air rising above a heater is an example of…

convection

a 60-gram sample occupies 20 cubic centimeters. Its density is…

3 g/cm³

salt helps melt ice in cold conditions mainly because it…

lowers water’s freezing point

a solution with pH 3 is generally …

acidic

which cell structure contains most of the DNA in a typical human cell?

nucleus

which blood cells primarily carry oxygen?

red blood cells

which organ pumps blood through the circulatory system?

heart

photosynthesis converts light energy primarily into…

chemical energy

the regular day / night cycle is caused mainly by Earth’s …

rotain

Earth’s seasons are caused mainly by …

Earth’s axial tilt as it orbits the Sun

ocean tides are strongly influenced by the gravity of the …

moon

rock formed when magma or lava cools is …

igneous

fog forming on a cool surface is an example of …

condensation

which material is typically the best thermal insulator?

fiberglass

a catalyst generally …

speeds a reaction without being used up overall

which change is a physical change rather than a chemical change?

ice melting

which is the basic functional unit of the kidney?

nephron

sound travels fastest, in general, through …

solids

at standard atmospheric pressure, pure water freezes at approximately…

0°C

which gas do plants take in for photosynthesis?

carbon dioxide