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Term
Definition
Constant   variable that stays the same during an experiment  
Control   sample that is treated like other experimental groups except that the independent variable is not applied to it  
Dependent Variable   factor that is being measured during an experiment  
Experimental Research Design   used to answer scientific questions by testing a hypothesis through the use of a series of carefully controlled steps  
Hypothesis   prediction or statement that can be tested and may be formed by prior knowledge, any previous observations, and new information  
Independent Variable   variable that can be changed during an experiment  
Model   represents something that is too big, too small, too dangerous, too time consuming, or too expensive to observe directly  
Science   process used to investigate what is happening around us in order to solve problems or answer questions  
Scientific Method   ways to solve problems that can include step by step plans, making models, and carefully thought out experiments  
Technology   application of science to make useful products and tools, such as computers  
Alpha Particle   consists of a particle containing two protons and two neutrons  
Atomic Number   number of protons in the nucleus of an atom of a given element  
Beta Particle   a high-energy electron that comes from the nucleus  
Electron   negatively- charged particle that exists in an electron cloud formation around an atom's nucleus  
Electron Cloud   region surrounding the nucleus of an atom, where electrons are most likely to be found  
Element   substance that cannon be broken down into simpler substances  
Half-Life   time needed for one half of the mass of a sample of a radioactive isotope to decay  
Isotope   atoms of the same element that have different numbers of neutrons  
Mass Number   the sum of neutrons and protons in the nucleus of an atom  
Neutron   electrically neutral particle that has the same mass as a proton and is found in an atom's nucleus  
Proton   positively charged particle in the nucleus of an atom  
Radioactive Decay   release of nuclear particles and energy from unstable atomic nuclei  
Transmutation   the change of one element into another through radioactive decay  
Actinides   the second series of inner transition elements which goes from thorium to lawrencium  
Alkali Metals   elements in group 1 of the periodic table  
Alkaline Earth Metals   elements in group 2 of the periodic table  
Catalyst   substance that speeds up a chemical reaction but is not used up itself or permanently changed  
Group   family of elements in the periodic table that have similar physical or chemical properties  
Halogens   any element in group 17 of the periodic table  
Lanthanides   the first series of inner transition elements which goes from cerium to lutetium  
Metal   element that has luster, is malleable, ductile, and a good conductor of heat and electricity  
Metalloid   element that shares some properties with both metal and nonmetals  
Nobel Gases   elements in group 18 of the periodic table  
Nonmetal   element that is usually a gas or brittle solid at room temperature and is a poor conductor of heat and electricity  
Period   horizontal row of elements in the periodic table whose properties change gradually and predictably  
Representative Element   elements in groups 1 and 2 and 13-18 in the periodic table that include metals, metalloids, and nonmetals  
Semiconductor   element that does not conduct electricity as well as a metal but conducts it better than a nonmetal  
Transition Elements   elements in groups 3-12 in the periodic table, all of which are metals  
Chemical Bond   force that holds two atoms together  
Chemical Formula   combination of chemical symbols and numbers that indicates which elements and how many atoms of each element are present in a molecule  
Compound   pure substance that contains two or more elements  
Covalent Bond   chemical bond formed when atoms share electrons  
Electron Cloud   region surrounding the nucleus of an atom, where electrons are most likely to be found  
Electron Dot Diagram   chemical symbol for an element surrounded by as many dots as there are elements in its outer energy level  
Energy Level   the different positions for an electron in an atom  
Ion   atom that is positively or negatively charged because it has gained or lost one or more electrons  
Ionic Bond   attraction that holds oppositely charged ions close together  
Metallic Bond   bond formed when metal atoms share their pooled electrons  
Molecule   neutral particle formed when atoms share electrons  
Polar Bond   bond resulting from the unequal sharing of electrons  
Activation Energy   minimum amount of energy needed to start a chemical reaction  
Catalyst   substance that speeds up a chemical reaction but is not used up itself or permanently changed  
Chemical Equation   shorthand form for writing what reactants are used and what products are formed in a chemical reaction  
Chemical Reaction   process that produces chemical change, resulting in new substances that have properties different from those of the original substances  
Concentration   describes how much solute is present in a solution compared to the amount of solvent  
Endothermic Reaction   chemical reaction in which heat energy is absorbed  
Enzyme   a type of protein that regulates chemical reactions in cells without being changed or used up itself  
Exothermic Reaction   chemical reaction in which heat energy is released  
Inhibitor   substance that slows down a chemical reaction, making the formation of a certain amount of product take longer  
Rate of Reaction   measure of how fast a chemical reaction occurs  
Acceleration   equals the change in velocity divided by the time for the chance to take place, occurs when an object speeds up or slows down  
Average Speed   equals the total distance traveled divided by the total time taken to travel the distance  
Inertia   tendency of an object to resist a change in its motion  
Instantaneous Speed   the speed of an object at one instant of time  
Law of Conservation of Momentum   states that the total momentum of objects that collide with each other is the same before and after the collision  
Mass   amount of matter in an object  
Momentum   a measure of how difficult it is to stop a moving object; equals the product of mass and velocity  
Speed   equals the distance traveled divided by the time it takes to travel that distance  
Velocity   speed and direction of a moving object  
Second   SI unit of measurement for time  
Meter   SI unit of measurement for length  
Kilogram   SI unit of measurement for mass  
Kelvin   SI unit of measurement for temperature  
Amperage   SI unit of measurement for electrical current  
Candle   SI unit of measurement for luminous intensity  
Mole   SI unit of measurement for amount of a substance