Download 8th Grade - Chemistry

8th Grade Chemistry Core Science Vocabulary
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acid
A substance that tastes sour, reacts with metals and carbonates, and turns blue litmus
paper red. An acid is a solution that contains more than 50% of H+. For example, acidic
foods include lemons, grapefruits, oranges, and limes. (pg. 268)
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base
(alkaline)
A substance that tastes bitter, feels slippery, and turns red litmus paper blue. A base is
a solution that contains more than 50% of OH-. For example, common bases are
sodium hydroxide (baking soda), soaps, and detergents. (pg. 271)
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catalyst
A material that increases the rate of a reaction by lowering the activation energy
needed for the reaction to occur. For example, heat and enzymes are catalysts which
can speed up chemical reactions. (pg. 239)
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endothermic
reaction
A reaction that absorbs energy from the environment in the form of heat (thermal
energy). For example, ice turning into liquid water is an endothermic reaction. (pg. 220)
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exothermic
reaction
A reaction that releases energy in the form of heat. For example, liquid water turning
into ice, and the combustion of fuel are exothermic reaction (pg. 221)
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ion
An atom or group of atoms that has become electrically charged.
Examples of ions are H+ (hydrogen ion), OH- (hydroxide ion), Na+
(sodium ion), and Cl- (chloride ion). (pg. 185)
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isotope
An atom with the same number of protons and a different number of neutrons from
other atoms of the same element. For example, hydrogen has three isotopes. Protium
has zero neutrons, deuterium has one neutron, and tritium has two neutrons. (pg. 130)
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organic
compounds
Compounds that contain the element carbon. Organic compounds are found in all
living things, in products from living things, and in many man-made materials. For
example, skin, paper, and gasoline are examples of organic compounds. (pg. 297)
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Periodic
Table of
Elements
A chart of the elements showing the repeating patterns of their properties. The
elements in a group, or family, have similar properties, and the properties such as the
number of valence electrons can be predicted from their location. The reactivity of
metals decreases from left to right across the periodic table. (pg. 132)
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pH scale
A range of values used to express the concentration of hydrogen ions (H+) in a
solution. An acidic solution has more concentration of hydrogen ions than a basic
solution. Acids are found from 0 to 6 pH; neutrals such as pure water are 7 pH and
bases are from 8 to 14 pH. (pg. 276)
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Polymer
A large organic molecule in which many smaller molecules are bonded together. The
smaller molecules are called monomers. The prefix poly- means “many”, and the prefix
mono- means “one.” Examples: alcohols, esters, plastics, Styrofoam, and DNA
molecules are all polymers. (pg.304)
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product
Substances formed as a result of a chemical reaction. Products are found on the right
side of a chemical equation. (pg. 216)
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reactant
Substances that enter into a chemical reaction that are changed into new substances
when the reaction is complete. The reactants are found on the left side of a chemical
equation. (pg. 216)
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sublimation
The change in state from a solid directly to a gas without passing through the liquid
state. For example, dry ice when exposed to room temperature goes from a solid to a
gas. (pg. 101)
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valence
electrons
The electrons that are in the highest energy level of an atom and that are involved in
bonding and chemical reactions. This carbon model has 4 valence electrons in the
outer most level. These 4 valence electrons will bond with other valence electrons from
other atom(s) in a chemical reaction. (pg. 176)
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