Amorphous:

 A type of solid matter in which atoms or molecules do not have long-range order (e.g., glass and plastic).

Atoms:

The smallest identifiable unit of an element.

calorie (cal):

the amount of energy required to raise the temperature of 1 g of water by 1 °C.

Calorie (Cal):

 An energy unit equivalent to 1000 little-c calories

Celsius (C) scale:

  A temperature scale often used by scientists.  On this scale, water freezes at 0 °C and boils at 100 °C at 1 atm pressure.  Room temperature is approximately 22 °C.

Chemical change:

A change in which matter changes its composition.

Chemical energy: 

The energy associated with chemical changes. 

Chemical property:

Properties that a substance can display only through changing its composition.

Chemical reaction:

 The process by which one or more substances transform into different substances via a chemical change.  Chemical reactions often emit or absorb energy.

Compound:

A substance composed of two or more elements in fixed, definite proportions.

Compressible:

 Able to occupy a smaller volume when subjected to increased pressure.  Gasses are compressible because in the gas phase, atoms or molecules are widely separated.

Crystalline:

  A type of solid matter with atoms or molecules arranged in a well-ordered, three-dimensional array with long-range, repeating order (e.g., salt and diamond).

Decanting:

The act of carefully pouring off one substance from another (as in pouring the oil off water).

Distillation: 

The process in which a mixture is heated to boil off the more volatile (easily vaporized) liquid.

Electrical energy: 

Energy associated with the flow of electric charge.

Element: 

A substance that cannot be broken down into simpler substances.

Endothermic:

Describes a process that absorbs heat energy. 

Energy: 

The capacity to do work.

Exothermic:

Describes a process that releases heat energy.

Fahrenheit (F) scale:

 The temperature scale that is most familiar in the United States; water freezes at 32 °F and boils at 212 °F at 1 atm pressure.

Filtration:

The process of pouring a mixture though filter paper to separate the solids from the liquid.

Gas:

A state of matter in which atoms or molecules are widely separated and free to move relative to one another.

Heat: 

The transfer or exchange of thermal energy caused by a temperature difference.

Heat capacity: 

The quantity of heat energy required to change the temperature of a given amount of substance by 1 °C.

Heterogeneous mixture: 

A mixture, such as oil and water, that has two or more regions with different compositions.

Homogeneous mixture:

 A mixture, such as salt water, that has the same composition throughout.

Kelvin (K) scale :

The temperature scale that assigns 0 K to the coldest temperature possible, absolute zero (-273 °C or -459 °F), the temperature at which molecular motion stops.  The size of the kelvin is identical to that of the Celsius degree. 

Kilowatt-hour (kWh):

A unit of energy equal to 3.6 million joules.

Kinetic energy:

Energy associated with the motion of an object. 

Law of Conservation of Energy: 

A law stating that energy can be neither created nor destroyed.  The total amount of energy is constant and cannot change; it can only be transferred from one object to another or converted from one form to another.

Liquid:

  A state of matter in which atoms or molecules are packed close to each other (about as closely as in a solid) but are free to move around and by each other.

Matter:

 Anything that occupies space and has mass.  Matter exists in three different states:  solid, liquid and gas.

Mixture:

 A substance composed of two or more different types of atoms or molecules combined in variable proportions.

Molecule:

 Two or more atoms joined in a specific arrangement by chemical bonds.  A molecule is the smallest identifiable unit of a molecular compound.

Physical change:

  A change in which matter does not change its composition, even though its appearance might change.

Physical property:

Those properties that a substance displays without changing its composition.

Potential energy:

 The energy of a body that is associated with its position or the arrangement of its parts.

Product:

  The final substances produced in a chemical reaction; represented on the right side of a chemical equation.

Property:

  The characteristics we use to distinguish one substance from another.

Pure substance:

A substance composed of only one type of atom or molecule.

Reactant:

 The initial substances in a chemical reaction, represented on the left side of a chemical equation.

Solid: 

A state of matter in which atoms or molecules are packed close to each other in fixed locations.

Specific heat capacity (specific heat):

 The heat capacity of a substance in joules per gram degree Celsius (J/g °C)

State of matter:

 The three forms in which matter can exist: solid, liquid, and gas.

Temperature:

 The measure of a substance’s thermal energy.

Thermal energy:

 Energy associated with the random motions of atoms and molecules in matter.

Volatile:

  Tending to vaporize easily.

Work:

 The result of a force acting on a distance.