|A water solution, indicated by the notation "(aq)". For example, HCl (aq) indicates a water solution of hydrochloric acid.
|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.
|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).
|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.
|A substance composed of two or more different elements chemically combined in a definite ratio. A compound can be decomposed by a chemical change.
|The change in state of matter from a gas (vapor) to a liquid. Heat is released in this phase change.
|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.
|Mass per unit volume.
|A phase change in which a gas turns directly into a solid, skipping the liquid phase; the settling out of material from a solution.
|A substance that cannot be decomposed by chemical change. All known elements are listed in the Periodic Table.
|A reaction in which the products contain more energy than the reactants. Energy is absorbed in an endothermic reaction.
|A change in state from liquid to gas; energy is absorbed.
|A reaction in which the products contain less energy than the reactants. Energy is released in an exothermic reaction.
|The change in phase of a substance from a liquid to a solid. The substance releases energy.
|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.
|A phase of matter that takes the shape and volume of its container. The gaseous phase of matter is represented by the notation "(g)".
|A unit of mass in the metric system; symbol is "g".
|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.
|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.
|A unit of energy .
|The energy of motion, as opposed to potential energy (energy of position). Temperature measures average kinetic energy
|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)".
|A measure of the amount of matter; often measured in grams (g).
|Anything that has mass and takes up space.
|A phase change from a solid to a liquid.
|A combination of two or more distinct substances differing in properties and composition. The composition of a mixture can vary.
|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.
|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.
|A change in the phase of matter or in its physical properties, such as shape, mass, volume, or density.
|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.
|A change from a solid directly into a gas without passing through the liquid phase.
|Matter in which all samples have identical properties and composition.
|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).
|Evaporation. The change in phase or state from a liquid to a vapor (gas). Evaporation of water is a cooling process.
|The amount of space occupied by matter.