General Chemistry/Properties of matter
The fundamental properties that we use to measure matter in are; Inertia, Mass, Weight, Volume, Density and Specific Gravity. The periodic table is a visual method of interpreting the chemical properties of elements which effect the measurements below.
These measurements can be classified into two categories, intrinsic and extrinsic.
Extrinsic properties (also called extensive), such as volume and weight, are directly related to the amount of material being measured.
- Inertia - the resistance of an object to changes in motion (Newton's first law).
- Measured as mass because it is intimately related to mass. Mass has inertia by virtue of its nature.
- Common units: kilograms (kg), grams (g), pounds (lb).
- Fundamental property of matter.
- Mass - a) the amount of matter in an object; b) a measure of resistance to acceleration that an object has.
- Common units; kilograms (kg), grams(g), pounds (lb), ounces (oz).
- Sometimes equated with weight, but only valid when the acceleration due to gravity is understood to be 9.81 m/s2 (i.e., earthly conditions), or when a different definition of the word "weight" is used, as is normal in commerce and the medical sciences.
- Mass times the acceleration of gravity.
- Note that Weight is very different from Mass, a common misconception for students. However, weight and mass are related. An easy way to remember the difference is that no matter what planet you are on, you will always be the same mass. However, if you enter a different planet or go on the moon, your weight will change.
- The measure of the attraction between two objects, one of which is generally much larger than the other.
- Common units: newtons (N), pounds-force (lbf), ounces-force (ozf).
- Common units: pounds-force (lbf) or newtons (N).
- Relevant equation(s):
- F = m a ( Force = Mass * acceleration )
- W = m g ( Weight = Mass * Gravity )
- N = 1 kg m/s2 ( newtons = kilograms * meters per second squared )
- Notes: The acceleration of gravity near the surface of the earth is 9.81 meters per second squared or 9.81 m/s2.
- Volume - the amount of space that an object occupies.
- Common units: liters (l), cubic meters (m³), cubic feet (ft³), fluid ounces, pints, quarts, gallons.
Intrinsic properties (also called intensive) are those which are independent of the quantity of matter present. For example, the density of gold is the same no matter how much gold you have to measure. Common intrinsic properties are density and specific gravity.
- Density - units of mass per unit of volume.
- Common units: g/cm3 and kg/m3
- Relevant equation(s):
- D = m/v ( Density = mass/volume )
- These measurements are relative to temperature. The density of water (at 4 degrees Celsius) is 1.00 g/cm3. Above and below that temperature, the density will be slightly different.
- Specific Gravity - ratio of a substance's density relative to the density of water. Usually table values use a water temperature of 25 degrees Celsius. See current reference books for examples.
- Since specific gravity is a ratio with the same numerator as denominator, it has no units.
- Specific gravity is usually measured with a hydrometer.
- Specific gravity can be an ambiguous measurement if the temperatures of the two substances are different.
- Specific Heat - the amount of energy required to raise the temperature of one gram of a pure substance by one degree Kelvin.
- Common units J/(g*K) (Joules per gram-Kelvin).