HESI-A2 CHEMISTRY

Chemistry note cards for HESI entrance exam Question Answer Matter that has a definite shape and volume solid Matter that changes in volume with changes in temperature and pressure gas A change of matter is when no change is made to the chemical composition of a substance. physical Simplest of substances and is represented by a letter or letters element Law that states matter can neither be created nor destroyed during a chemical reaction Law of conservation of mass The breaking of bonds and reforming of new bonds to create new chemical compounds with different chemical formulas and different chemical properties Chemical reaction 5 main chemical reactions synthesis, decomposition, combustion, single replacement, double replacement Chemical reaction in which 2 elements combine to form a product synthesis Chemical reaction that is the breaking of a compound into component parts decomposition The chemical reaction that is the reaction of a compound with oxygen combustion Chemical reaction that consists of an active metal reaction with an ionic compound creating a new compound single replacement Chemical reaction involving 2 ionic compounds; the reactant yields "switched partners" double replacement how elements are arranged on the periodic table by their chemical properties Number that represents the # of protons an element has atomic number average of the masses of each of its isotopes as they occur in nature atomic mass Mass number - atomic number = # of neutrons in an element Columns of the periodic table = groups Rows of the periodic table = periods Group IA = charge +1 Group IIA = charge +2 Group IIIA = charge +3 Group VA = charge -3 Group VIA = charge -2 Group VIIA = charge -1 Charge of noble gases 0 Positively charged ions protons Negatively charged ions electrons Neutral ions neutrons # of proteins in an element = atomic number proteins + neutrons = mass number In reactions, atoms try to reach stable electron configurations. chemical reactions take place in the nucleus, to obtain stable nuclear configurations. nuclear Word used to describe the emission of particles from an unstable nucleus. radioactivity The particles that are emitted during radioactivity radiation 3 types of radiation alpha, beta, gamma Radiation that is the emission of helium ions alpha Alpha radiation particles have a charge of +2 How can penetration from alpha particles be stopped? piece of paper Radiation that is a product of the decomposition of a neutron. It is composed of high-speed, high- energy electrons. beta radiation How can beta radiation particles be stopped? aluminum foil radiation is high-energy electromagnetic radiation that lacks charge and mass. gamma What radiation can be stopped by several feet of concrete or several inches of lead? gamma radiation 2 types of chemical bonding ionic & covalent What bond is an electrostatic attraction between 2 oppositely charged ions? (between metals & nonmetals) ionic A single bond is formed when 2 atoms share a pair of electrons. covalent A bond is formed when 2 electron pairs are shared. double covalent A bond is formed when 3 electron pairs are shared. triple covalent What is the strongest type of chemical bond? What is it formed by? covalent bond; non-metals In a covalent bond compound, if the electrons are shared equally, then the bond is . non-polar If electrons are not shared equally in a covalent bond, the bond is . polar is based on the difference in electronegativity values for the elements involved polarity Hydrogen bonding, dipole interactions and dispersion forces. intermolecular forces Bond that is the attraction for a hydrogen atom by a highly electronegative element. hydrogen bond Elements fluorine, chlorine, oxygen and nitrogen are generally involved in a bond. hydrogen Bond that is the strongest of the intermolecular forces hydrogen The attractions of one dipole for another dipole interactions A is created when an dipole electron pair in a covalent bond is shared unequally A dipole attraction is a intermolecular force. weak The weakest of all intermolecular forces. dispersion forces Dispersion forces are typically found in covalent compounds. Non-polar 6.02 x 10^23 is a mole The mass of one mole of a substance atomic mass The part of chemistry that deals with the quantities and numeric relationships between compounds in a chemical reaction. stoichiometry To balance an equation, are placed in front of each component. coefficient 4 ways to increase the reaction rate increase temperature, increase surface area, increase concentrations and reactants and add a catalyst Increasing the causes the particles to have greater kinetic energy, allowing them to move faster and have a greater chance temperature Accelerates a reaction by reducing the activation energy, or the amount of energy needed for a reaction to occur. catalyst reaction involve the transfer of electrons from one element to another redox The loss of electrons oxidation The gain of electrons reduction