Ch 2

• Science - attempts to discover order in nature and use that knowledge to make predictions about what it likely to happen in nature.
• Scientific method - the ways scientists gather data and formulate and test scientific hypotheses, models, theories, and laws.
• Data - factual information collected by scientists.
• Scientific hypothesis - a tentative explanation of a scientific law or certain scientific observations.
• Model - approximate representation or simulation of a system being studied.
• Scientific theory - a well-tested and widely accepted scientific hypothesis.
• Peer review - process of scientists reporting details of the methods and models they used, the results of their experiments, and the reasoning behind their hypotheses for other scientists working in the same field (their peers) to examine and criticize.
• Scientific law/Law of nature - description of what scientists find happening in nature repeatedly in the same way, without known exception.
• Reliable science - concepts and ideas that are widely accepted by experts in a particular field of science.
• Unreliable science - scientific results or hypotheses presented as reliable science without having undergone the rigors of the peer review process.
• Tentative science - preliminary scientific data, hypotheses, and models that have not been widely tested and accepted.
• Matter - anything that has mass (the amount of material in an object) and takes up space. On the earth, where gravity is present, we weigh an object to determine its mass.
• Element - chemical, such as hydrogen (H), iron (Fe), etc., whose distinctly different atoms serve as the basic building blocks of all matter. Two or more elements combine to form compounds that make up most of the world’s matter.
• Periodic table of elements - the organization of all known chemical elements according to atomic number, chemical properties, and electron configurations.
• Compounds - combination of atoms, or oppositely charged ions, of two or more elements held together by attractive forces called chemical bonds.
• Atom - minute unit made of subatomic particles that is the basic building block of all chemical elements and thus all matter; the smallest unit of an element that can exist and still have the unique characteristics of that element.
• Atomic theory - idea that all elements are made up of atoms; the most widely accepted scientific theory in chemistry.
• Neutrons - elementary particle in the nuclei of all atoms (except hydrogen-1). It has a relative mass of 1 and no electric charge.
• Protons - positively charged particle in the nuclei of all atoms. Each proton has a relative mass of 1 and a single positive charge.
• Electrons - tiny particle moving around outside the nucleus of an atom. Each electron has one unit of negative charge and almost no mass.
• Nucleus - extremely tiny center of an atom, making up most of the atom’s mass. It contains one or more positively charged protons and one or more neutrons with no electrical charge (except for hydrogen-1 atom, which has one proton and no neutrons in its nucleus).
• Atomic number - number of protons in the nucleus of an atom.
• Mass number - sum of the number of neutrons (n) and the number of protons (p) in the nucleus of an atom. It gives the approximate mass of that atom.
• Isotopes - two or more forms of a chemical element that have the same number of protons but different mass numbers because they have different numbers of neutrons in their nuclei.
• Molecule - combination of two or more atoms of the same chemical element (such as O 2 ) or different chemical elements (such as H 2 O ) held together by chemical bonds.
• Ion - atom or group of atoms with one or more positive (+) or negative (−) electrical charges.
• Acidity - comparative amounts of hydrogen ions (H+) and hydroxide ions (OH–) contained in a particular volume of a solution when a substance is dissolved in water. An acid solution has more hydrogen ions than hydroxide ions and a basic solution has more hydroxide ions than hydrogen ions.
• pH - numeric value that indicates the relative acidity or alkalinity of a substance on a scale of 0 to 14, with the neutral point at 7. Acidic solutions have a pH less than 7 and basic solutions have a pH greater than 7.
• Chemical formula - shorthand way to show the number of atoms (or ions) in the basic structural unit of a compound.
• Organic compounds - Compounds containing carbon atoms combined with each other and with atoms of one or more other elements such as hydrogen, oxygen, nitrogen, sulfur, phosphorus, chlorine, and fluorine. All other compounds are called inorganic compounds.
• Complex carbohydrates - molecules consisting of carbon, hydrogen, and oxygen that provide energy to living organisms. Sugar, starch, and cellulose are examples.
• Proteins - structural molecules consisting of a specific sequence of amino acids that serve as components of body tissue and as enzymes.
• Nucleic acids - informational molecules such as DNA or RNA in a double-helix shape consisting of complementary nucleotides in a specific sequence.
• Lipids - energy storing organic molecule such as fats, oils, and waxes.
• Cells - smallest living unit of an organism.
• Cell theory - the idea that all living things are comprised of cells.
• Genes - coded units of information about specific traits that are passed from parents to offspring during reproduction. They consist of segments of DNA molecules found in chromosomes.
• Trait - characteristic passed on from parents to offspring during preproduction in an animal or plant.
• Chromosome - a grouping of genes and associated proteins in plant and animal cells that carry certain types of genetic information.
• Physical change - process that alters one or more physical properties of an element or a compound without changing its chemical composition.