biology ch 2 quiz

Matter : Anything that occupies space and has mass.

Element : A substance that cannot be broken down into other substances by ordinary chemical means.

Compound : A substance made of two or more different elements combined in a fixed ratio.

Emergent property : A property that appears when components are combined and differs from the properties of the individual components.

Essential elements : Elements required by organisms to survive and function.

CHNOPS : Carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur—the major elements associated with living matter.

Trace element : An element required by an organism in very small amounts.

Atom : The smallest unit of matter that retains the properties of an element.

Subatomic particles : Protons, neutrons, and electrons.

Proton : A positively charged particle found in the nucleus.

Neutron : A neutral particle found in the nucleus.

Electron : A negatively charged particle found outside the nucleus.

Nucleus : The dense central region of an atom containing protons and neutrons.

Atomic number : The number of protons in an atom.

Mass number : The total number of protons and neutrons in an atom.

Isotope : A form of an element with the same number of protons but a different number of neutrons.

Radioactive isotope : An unstable isotope whose nucleus decays spontaneously and releases particles and energy.

Radioactive tracer : A radioactive isotope used to track atoms during biological processes.

Electron shell : An energy level surrounding the nucleus where electrons are found.

Electron orbital : A region of space where an electron is most likely to be found.

Valence shell : The outermost electron shell of an atom.

Valence electrons : Electrons located in the outermost electron shell that determine an atom's chemical behavior.

Chemical bond : An attraction that holds atoms together.

Covalent bond : A bond formed when atoms share electrons.

Molecule : Two or more atoms held together by covalent bonds.

Nonpolar covalent bond : A covalent bond in which electrons are shared equally.

Polar covalent bond : A covalent bond in which electrons are shared unequally.

Electronegativity : An atom's ability to attract shared electrons toward itself.

Polar molecule : A molecule with an uneven distribution of electrical charge.

Ion : An atom or molecule with an electrical charge caused by gaining or losing electrons.

Cation : A positively charged ion.

Anion : A negatively charged ion.

Ionic bond : An attraction between oppositely charged ions.

Hydrogen bond : A weak attraction between a partially positive hydrogen and a nearby electronegative atom.

Chemical reaction : A process that breaks and forms chemical bonds and rearranges atoms.

Reactants : The starting substances in a chemical reaction.

Products : The substances produced by a chemical reaction.

Law of conservation of matter : Chemical reactions rearrange atoms but do not create or destroy them.

Cohesion : Attraction between molecules of the same substance.

Adhesion : Attraction between molecules of different substances.

Surface tension : A measure of how difficult it is to stretch or break the surface of a liquid.

Heat : The total energy associated with the movement of molecules in a substance.

Temperature : A measure of the average speed of molecules in a substance.

Evaporative cooling : Cooling that occurs when high-energy molecules evaporate, leaving behind molecules with lower average energy.

Solution : A uniform mixture of two or more substances.

Solvent : The substance that does the dissolving in a solution.

Solute : The substance being dissolved in a solution.

Aqueous solution : A solution in which water is the solvent.

Acid : A substance that donates H+ to a solution.

Base : A substance that accepts H+ from a solution.

Hydrogen ion (H+) : A positively charged hydrogen ion.

Hydroxide ion (OH−) : A negatively charged hydroxide ion.

pH scale : A scale from 0 to 14 that measures the H+ concentration of a solution.

Acidic solution : A solution with a pH below 7 and a relatively high H+ concentration.

Neutral solution : A solution with a pH of 7.

Basic solution : A solution with a pH above 7 and a relatively low H+ concentration.

Buffer : A substance that minimizes changes in pH by accepting or donating H+.

Acid precipitation : Rain, snow, or fog with a pH below about 5.2.

Ocean acidification : A decrease in ocean pH caused largely by increased CO2 dissolving in seawater.

Carbonic acid : An acid formed when CO2 dissolves in water.

Calcification : The process by which organisms such as corals produce shells or skeletons using carbonate ions.