Physical Science Heat and Matter

Matter Anything that occupies space and has mass Ex. Air Law of Conservation of Matter Matter is neither created or destroyed It is only changed from one form to another Solid, liquid, gas, and plasma are states or phases of matter

Kinetic Molecular Theory All matter is made up of tiny atoms and molecules that interact physically Molecules are separated by empty space All molecules are in constant motion (kinetic energy) Kinetic energy increases as heat is added and decreases as heat is removed

Phases of Matter - Solids Definite shape and volume Rigid 3-D structure Atoms/molecules bonded in place Allowed motions restricted to vibration in place only

Phases of Matter - Liquids Definite volume, indefinite shape Only weak cohesive bonds between component molecules Constituent molecules mostly in contact Allowed motions Vibration Rotation

Phases of Matter - Gases Indefinite volume and shape Molecules mostly not in contact Allowed motions Vibration and rotation (molecules with more than one atom) Random, mostly free paths

Phases of Matter - Plasma Plasma A very hot gas consisting of atoms that have been stripped of their electrons because of high kinetic energies For a picture, see the link below 2.jpg 2.jpg

Phase Changes Solid/liquidLiquid/gasSolid/gas Temperature (Direction ->) MeltingBoilingSublimation Temperature (Direction <-) FreezingCondensationSublimation

Evaporation and Condensation Individual molecules can change phase any time Evaporation: Energy required to overcome phase cohesion Higher energy molecules near the surface can then escape Condensation: Gas molecules near the surface lose KE to liquid molecules and merge

Heat A form of energy transfer between two objects Energy always moves from higher temperature regions to lower temperature regions Calorie (cal) – unit of energy needed to raise temperature of 1 g of water 1 degree Celsius

Temperature A measure of the internal energy of an object Thermometers Used to measure temperature Temperature measured in degrees 2 temperature scales Celsius: water freezes at 0 0 and boils at Fahrenheit: water freezes at 32 0 boils at 212 0

Water Major constituent of living things “Universal solvent” Dissolves most molecules Solid phase less dense than liquid Ice floats! High specific heat Amount of heat (energy) needed to increase the temperature of 1 gram of water 1 degree Celsius Cohesion Attractive forces between like molecules Adhesion Attractive forces between unlike molecules

Heat flow Three mechanisms for heat transfer due to a temperature difference 1. Conduction 2. Convection 3. Radiation Natural flow is always from higher temperature regions to cooler ones

Conduction Heat flowing through matter (solids) Mechanism Hotter atoms collide with cooler ones, transferring some of their energy Direct physical contact required; cannot occur in a vacuum Poor conductors = insulators (Styrofoam, wool, air…)

Convection Energy transfer through the bulk motion of hot material (liquids and gases) Examples Space heater Gas furnace (forced) Natural convection mechanism - “hot air rises”

Radiation Radiant energy - energy associated with electromagnetic waves Can operate through a vacuum All objects emit and absorb radiation Temperature determines Emission rate Intensity of emitted light Type of radiation given off Temperature determined by balance between rates of emission and absorption Example: Global warming

Study Websites What Is Matter?: Properties and Classification of Matter The Particle Nature of Matter: Solids, Liquids, and Gases Physical Changes and Conservation of Matter Chemical Changes and Conservation of Matter Density and Pressure Rising and Sinking Water Properties Heat and Temperature

GACE II Information- ECE/MG Water Freezing point Kinetic energy of molecules reduced enough to allow crystallization Presence of solute particles interferes with crystal formation lowers the freezing point (freezing point depression) Example: Salt excluded from ice as seawater freezes Ice is practically pure water Salinity of seawater increases Example: Antifreeze, ethylene glycol Boiling point Normal boiling point Temperature where vapor pressure = average sea level atmospheric pressure Vapor pressure over a solution less than that of the pure solvent Solute particles displace solvent particles on surface, hindering vaporization Leads to higher boiling point

GACE II Information- MG Interpreting Diagrams that Illustrate Changes in the Physical States of Matter %20Diagrams.doc %20Diagrams.doc