Unit 1: Matter

Pregunta	Respuesta
Aqueous	A water solution, indicated by the notation "(aq)". For example, HCl (aq) indicates a water solution of hydrochloric acid.
Atom	The smallest particle of an element that represents its physical and chemical properties.
Average Kinetic Energy	Energy of motion; the temperature of a substance is a measure of its average kinetic energy.
Boiling Point	The temperature at which a phase change occurs from liquid to gas as energy is absorbed. A liquid will boil at the temperature at which its vapor pressure equals the pressure on the liquid (atmospheric pressure).
Celsius	A temperature scale with set points of 0° for the freezing point of water at 1 atm (the ice-water equilibrium), and 100° for the boiling point of water at 1 atm (the water-steam equilibrium); abbreviated as "°C".
Chemical Reaction (Change)	The formation of a new substance with its own physical and chemical properties. Examples of chemical reactions include: single replacement, double replacement (substitution), decomposition, and synthesis.
Compound	A substance composed of two or more different elements chemically combined in a definite ratio. A compound can be decomposed by a chemical change.
condensation	The change in state of matter from a gas (vapor) to a liquid. Heat is released in this phase change.
Crystal	A solid with a regular geometric pattern. All true solids have a crystalline structure. Crystals contain particles arranged in a regular geometric pattern. Particles of matter are constantly vibrating even in the solid phase.
Density	Mass per unit volume.
Deposition	A phase change in which a gas turns directly into a solid, skipping the liquid phase; the settling out of material from a solution.
Element	A substance that cannot be decomposed by chemical change. All known elements are listed in the Periodic Table.
Endothermic Reaction	A reaction in which the products contain more energy than the reactants. Energy is absorbed in an endothermic reaction.
Evaporation	A change in state from liquid to gas; energy is absorbed.
Exothermic Reaction	A reaction in which the products contain less energy than the reactants. Energy is released in an exothermic reaction.
freezing	The change in phase of a substance from a liquid to a solid. The substance releases energy.
Freezing Point	The temperature at which a substance changes from a liquid to the solid phase. Contrast with the melting point. At the freezing point, both the liquid and solid phases are in equilibrium at atmospheric pressure.
Gas	A phase of matter that takes the shape and volume of its container. The gaseous phase of matter is represented by the notation "(g)".
Gram	A unit of mass in the metric system; symbol is "g".
Heat	A flow of energy from an area of higher temperature to an area of lower temperature.
Heat of Vaporization	The energy required to vaporize a unit mass of a liquid at its normal boiling point.
Heating and Cooling Curve	A graph representing the changes in the phases of matter.
Kelvin	An absolute temperature scale; the temperature measured in Kelvins is equal to the temperature in degrees Celsius + 273. The span of 1 K is equal to the span of 1°C. 0 K = absolute zero = −273°C.
Joule	A unit of energy .
Kinetic Energy	The energy of motion, as opposed to potential energy (energy of position). Temperature measures average kinetic energy
Liquid	A phase of matter that has definite volume but takes the shape of its container. Matter in the liquid phase indicated by the notation "(l)".
Mass	A measure of the amount of matter; often measured in grams (g).
Matter	Anything that has mass and takes up space.
melting	A phase change from a solid to a liquid.
Mixture	A combination of two or more distinct substances differing in properties and composition. The composition of a mixture can vary.
Molecule	The smallest particle of an element or compound capable of independent existence and formed by covalently bonded atoms in a definite ratio. A molecular compound can be decomposed by a chemical change.
Phase change	Change in state of matter. The addition or removal of heat energy can cause the form of matter to change between solid, liquid, and vapor.
Physical Change	A change in the phase of matter or in its physical properties, such as shape, mass, volume, or density.
Potential Energy	Energy of position rather than of motion, such as the energy stored in a chemical bond; contrast with kinetic energy.
Specific heat capacity	The amount of energy (in joules) it takes to raise the temperature of one gram of a substance by 1 Kelvin.
Specific Heat of Water	The amount of heat needed to raise the temperature of 1 gram of water by 1 Kelvin; a heat value equal to 4.18 J/g·K.
Standard Temperature and Pressure (STP)	For any gas, STP is defined as 0°C (273 K) and 760 mm of mercury (760 torr), or 101.3 kPa (kilopascals) or 1 atmosphere, of pressure.
Sublimation	A change from a solid directly into a gas without passing through the liquid phase.
Substance	Matter in which all samples have identical properties and composition.
Temperature	A measure of the average kinetic energy of the molecules that make up a substance; how "hot" or "cold". Temperature is measured in degrees Celsius (°C) or Kelvin (K).
Vaporization	Evaporation. The change in phase or state from a liquid to a vapor (gas). Evaporation of water is a cooling process.
Volume	The amount of space occupied by matter.

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