Matter, Mass, Density, Pressure, Temperature

Matter, Mass, Density, Pressure, Temperature Working toward basic Thermodynamics and Fluid Theory

Matter • Defined: • Anything that occupies space and has a mass • Substances are composed of small particles called atoms.

Molecules • Atoms combine to form more complex structures we call molecule • In general – • Electrically neutral group of two or more atoms held together • Covalent bonds • Different from Ions! • Compounds versus molecules • All compounds are molecules – not all molecules are compounds • Compounds consist of 2 different elements (eg. H20) • Molecular H2, O2, N2 are NOT compounds (molecules are of a single element • CO2, H2O, CH4 are compounds (2 different types of elements

Mass • The ‘amount of substance or matter’ • A natural unit for mass is the mass of a proton or neutron • AMU – atomic mass unit • 1 slug = 14.59 kg = 8.79 x10 27amu • 1 kg = 6.02 x 10 26

Density • Mass of a sample of the material divided by the volume of the same sample

Specific Gravity • Density comparison to water • How dense is substance with respect to water

Pressure • Defined as the force divided by the area on which it acts

Atmospheric Pressure • We live under a ‘blanket of air’ • Density of air decreases with altitude Sea Level: • 14.7 psi • 29.92 in. Hg

Absolute Pressure and Gage Pressure • ATM + Gage pressure = absolute pressure

Temperature • Hot vs Cold • Kinetic Energy of molecules • Expansion of objects when heated • Use of thermometers

K = C +273 R = F + 460

Matter, Mass, Density, Pressure, Temperature