act science

atoms

the basic units of matter

molecules

two or more atoms chemically bonded together

elements

pure substances made of one type of atom

compounds

substances made of multiple elements chemically bonded together

chemical formulas

Subscripts indicate the number of atoms.

chemical reaction arrows

→ means “produces” or “yields,” while ⇌ indicates that a reaction occurs in both directions (equilibrium)

concentration

The amount of substance present in a certain volume

dissolving

When one substance becomes evenly distributed in another.

gas vs liquid vs solid

Solids have a fixed shape and volume, liquids have a fixed volume and change shape, and gasses have no fixed shape or volume.

condensation

gas to liquid

evaporation

liquid to gas

melting

solid to liquid

freezing

liquid to solid

density

Objects with high density have more mass packed into a given volume. Objects float if they are less dense than the fluid around them.

conservation of mass

Matter is not created or destroyed during chemical reactions.

cell

basic unit of life

tissue

Group of similar cells working together.

organ

Group of tissues working together for a specific function.

organism

living thing

species

A group of organisms capable of reproducing together.

ecosystem

Living organisms interacting with their environment.

photosynthesis

Plants use sunlight to produce glucose. Plants need sunlight, water, and carbon dioxide.

cellular respiration

Cells break down glucose to release energy.

hormones

Chemical messengers in organisms

DNA

Genetic material carrying instructions for life.

endotherm

Animals that generate body heat internally, like mammals and birds.

ectotherm

Animals that rely mostly on environmental heat, like reptiles and amphibians.

reptiles

Cold-blooded vertebrates with scales.

amphibians

Cold-blooded vertebrates that usually live partly in water.

mammals

Warm-blooded vertebrates with hair/fur that produce milk.

fish

Aquatic vertebrates that use gills.

osmosis

Movement of water across a membrane from high water concentration to low water concentration.

speed

Distance traveled per unit time.

velocity

Speed with direction.

acceleration

Rate of change in velocity.

force

A push or pull.

gravity

Force pulling objects toward Earth.

friction

Force resisting motion between surfaces.

energy

Ability to do work.

kinetic energy

Energy of motion.

potential energy

Stored energy.

temperature

Measure of average particle motion.

heat

Transfer of thermal energy.

frequency

How often something occurs. A common example is sound waves per second.

waves

Transfer energy through matter or space.

sound waves

Mechanical waves that travel through matter.

light

Electromagnetic radiation.

electrons

Negatively charged particles.

protons

Positively charged particles.

neutrons

Neutral particles.

electrical charges

Opposite charges attract while like charges repel.

magnetic fields

Regions where magnetic forces act.

mass

Amount of matter in an object.

weather

Short-term atmospheric conditions

climate

Long-term weather patterns.

erosion

Movement of sediment by wind, water, or ice.

sediment

Small particles of rock or soil.

albedo

Reflectiveness of a surface.

solar radiation Energy coming from the Sun.

Energy coming from the Sun.

atmosphere

Layer of gases surrounding Earth.

tectonic plates

Large moving sections of Earth’s crust.

fault line Boundary where tectonic plates meet.

Boundary where tectonic plates meet.

fossils

Preserved remains or traces of ancient organisms.