WORD
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DEFINITION
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Acid
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A substance that donates hydrogen ions. Any compound that produces hydrogen ions (H+) in water thereby reducing the pH of water to a value below 7.
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Atom
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The smallest part of a substance which can exist and still retain the properties of that substance.
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Atomic Number
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Number of protons in the nucleus of one atom of an element.
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Base
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A substance that accepts hydrogen ions. Any compound that produces hydroxide ions (OH-) in water thereby raising the pH of water to a value above 7.
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Boiling Point
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The temperature at which a substance in its liquid state changes into a gas state.
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Celsius
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A temperature scale in which the freezing point of water is 0° and the boiling point of water is 100°.
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Chemical change
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A change that results in the formation of a new substance, such as the burning of wood.
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Chemical energy
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Energy stored in the chemical bonds of molecules.
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Chemical properties
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Properties which cause specific behavior of substances during chemical reactions, such as reacts with oxygen, reacts with acids, reacts with bases.
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Chemical reaction
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Change that takes place when two or more substances (reactants) interact to form new substances (products).
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Chromatography
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Process of separating small amounts of substances from mixtures by the rates at which they move through or along a medium.
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Composition
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The chemical make up of a given substance.
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Compound
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A substance in which the atoms of different elements are bonded to one another. It can be broken down into simpler parts only by a chemical change.
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Condensation
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Process in which matter changes from a gaseous state to a liquid state.
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Crystal
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A solid with a definite shape, formed from a repeating pattern of atoms.
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Electron
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The negatively charged particle that moves around the nucleus of an atom.
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Element
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A substance that consists of only one kind of atom and cannot be broken down into simpler parts during a chemical reaction.
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Evaporation
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Change of matter from a liquid state to a gaseous state at a temperature below its boiling point.
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Expand
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When most substances are heated their molecules move faster and further apart causing them to increase.
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Filtration
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Process of separating a liquid and a solid by pouring the mixture through a fine mesh.
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Gas
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The state in which a substance has no definite shape or volume.
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Indicator
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A substance that changes color when it comes in contact with an acid or a base.
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Kinetic energy
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Energy of motion.
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Law of Conservation of Mass
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Mass can be neither created nor destroyed during a chemical reaction- only changed from one form to another.
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Liquid
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The state in which a substance flows and takes up the shape of its container.
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Litmus paper
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An indicator which shows whether a solution is acidic or basic (acids turn blue litmus paper red; bases turn red litmus paper blue).
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Malleability
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Ability of a substance to be molded into different shapes.
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Mass
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A measure of the amount of matter in an object.
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Mass number
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The number of protons and neutrons in the nucleus of an atom.
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Matter
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Anything that has volume and mass.
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Mechanical energy
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Energy an object has because of its motion or position.
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Metals
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Elements that usually have luster, conduct heat energy and electricity, and usually bend without breaking.
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Mixture
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A combination of two or more substances that have not combined chemically and that can be separated by physical means.
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Molecule
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The smallest unit of a substance that has all of the physical and chemical properties of the substance and that is composed of two or more atoms.
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Neutral
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A substance that does not have the properties of an acid or a base, but has an equal number of hydrogen and hydroxide ions. It has a pH of 7.
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Neutral atom
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An atom with an equal number of protons and electrons is electrically neutral.
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Noble gases
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Group of elements in the periodic table that generally do not react with other elements, such as neon and krypton.
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Nonmetals
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Elements that in general do not conduct electricity, are poor conductors of heat, and are brittle when solid.
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Periodic table
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A chart where all elements are organized into periods and groups according to their properties.
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pH scale
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Scale ranging from 0-14, used to describe how acidic (0) or basic (14) a substance is. The pH is the measure of the hydrogen ion concentration in a solution.
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Physical change
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A change that occurs in the physical property/properties of a substance without altering its composition.
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Potential energy
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The stored energy of a body because of its position.
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Proton
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Positively charged particles in the nucleus of an atom.
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Reactant
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Compound or element that changes during a chemical reaction.
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Reactivity
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Ability of an element to gain or lose electrons which are used for bonding.
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Solid
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The state in which a substance has a definite volume and shape and resists forces which try to change these.
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Solubility
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Ability of a substance to dissolve in another substance.
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Solution
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Mixture in which the molecules of one substance (solute) are dissolved in another substance (solvent).
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State of matter
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The forms matter can take, as in liquid, solid, or gas.
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Substance
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Matter of a particular kind, or chemical makeup.
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Temperature
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The measure of the average energy of motion of the particles of a substance.
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Volume
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Amount of space an object or substance takes up; measured in liters or cubic centimeters.
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