AP Environmental Science Chapter 2

Chemistry unit of environmental science

Basic

A substance with a pH greater than 7; also known as alkaline.

Carbohydrates

Organic compounds made of carbon, hydrogen, and oxygen; used for energy by organisms.

Carbon

A key element in all living organisms; central to organic compounds.

Carbon Dioxide (CO₂)

A colorless gas produced by respiration and combustion; used by plants in photosynthesis.

Cellular Respiration

Process where organisms convert glucose and oxygen into energy, releasing CO₂ and water.

Chemistry

The study of matter and how it interacts with energy and other matter.

Chemosynthesis

Process where some organisms use chemical energy (not sunlight) to produce food.

Compound

A substance made of two or more different elements chemically bonded.

Continental Collision

When two continental plates converge, forming mountain ranges.

Convergent Plate Boundary

Where two plates move toward each other, often forming mountains or subduction zones.

Core

The innermost layer of Earth, composed mostly of iron and nickel.

Covalent Bond

A chemical bond where atoms share electrons.

Crust

Earth's outermost solid layer.

Deoxyribonucleic Acid (DNA)

The molecule that carries genetic information in organisms.

Divergent Plate Boundary

Where tectonic plates move apart, creating new crust (e.g., mid-ocean ridges).

Efficiency

The ratio of useful energy output to total energy input in a system.

Energy

The capacity to do work or cause change.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed.

Genes

Segments of DNA that code for traits or proteins.

Geology

The study of Earth's physical structure and substances.

Half-Life

Time it takes for half of a radioactive substance to decay.

Heterotrophs

Organisms that consume other organisms for energy (e.g., animals).

Hydrocarbons

Organic compounds made of hydrogen and carbon; found in fossil fuels.

Hydrothermal Vents

Openings on the seafloor that release heated, mineral-rich water.

Igneous Rocks

Formed from cooled molten rock (magma or lava).

Ionic Bonds

Chemical bonds formed by the transfer of electrons between atoms.

Ionizing Radiation

High-energy radiation that can remove electrons from atoms and damage DNA.

Ions

Charged atoms or molecules (positive = cation, negative = anion).

Isotopes

Atoms of the same element with different numbers of neutrons.

Matter

Anything that has mass and takes up space.

Metamorphic Rock

Rock altered by heat, pressure, or chemically active fluids.

Methane (CH₄)

A potent greenhouse gas produced naturally and by human activity.

Mineral

A naturally occurring, inorganic solid with a definite chemical composition.

Molecules

Two or more atoms bonded together.

Neutrons

Neutral particles in an atom's nucleus.

Nitrogen

A major component of the atmosphere; essential for proteins and DNA.

Nucleic Acids

DNA and RNA; molecules that store and transmit genetic information.

Organic Compounds

Carbon-based compounds typically found in living organisms.

Oxygen

An essential gas for most life; used in respiration, byproduct of photosynthesis.

Ozone (O₃)

A molecule that absorbs UV radiation in the stratosphere.

pH

A measure of acidity or alkalinity on a scale of 0–14.

Photosynthesis

Process by which plants convert sunlight, CO₂, and water into glucose and O₂.

Plastics

Synthetic polymers made from petrochemicals; widely used and persistent in the environment.

Plate Tectonics

The theory that Earth's crust is divided into plates that move.

Protons

Positively charged particles in an atom’s nucleus.

Radioactive

Materials that emit radiation as their nuclei decay.

Ribonucleic Acid (RNA)

A molecule involved in protein synthesis; works with DNA.

Rock

A solid aggregate of minerals.

Rock Cycle

The continuous transformation of rocks from one type to another.

Second Law of Thermodynamics

In energy transformations, some energy is lost as heat; entropy increases.

Sedimentary Rocks

Rocks formed by the compaction and cementation of sediments.

Sediments

Particles of rock, sand, or organic material transported and deposited by wind, water, or ice.

Silicon

A common element in Earth’s crust, especially in silicate minerals.

Subduction

When one tectonic plate sinks beneath another.

Transform Plate Boundary

Where two plates slide past each other, causing earthquakes.

Tsunami

A large sea wave caused by underwater earthquakes or volcanic eruptions.

Uranium

A radioactive element used as fuel in nuclear reactors.

Volcano

An opening in Earth’s surface where magma, gases, and ash erupt.

Water

A vital molecule (H₂O) essential for life and many environmental processes.