The Gas Laws
Vocabulary Pressure Absolute zero Charles Law Boyle s Law (take a moment to look up and record definitions in your notes)
Key Concepts What causes gas pressure in a closed container? What factors affect gas pressure? How are the temperature, volume, and pressure of a gas related?
Pressure Pressure is the result of force applied over an area The smaller the area the greater the pressure produced SI unit of pressure comes from the units of force and area P = f(n)/a(m2); P (N/m2); 1 N/m2 = Pa (pascal)
Pressure (cont.) Objects do not need to be large to exert pressure ex.) helium molecules in a balloon Collisions between particles of a gas and the walls of the container cause the pressure in a closed container of gas.
Factors That Affect Gas Pressure Factors that affect Gas Pressure are: Temperature Volume Number of Particles
Temperature As temperature rises, the average kinetic energy of particles in the gas increase more collisions equals more pressure (with volume and #particles constant) Will a tire have more pressure on a cold morning or a warm morning? Put a balloon in the microwave and one in the freezer what happens? (don t do it without permission from your parents)
Volume Squeezing a juice box or bottle of water what happens? (similar to what happens to a gas) When you reduce the volume of a gas, the pressure increases (temp and # particles constant)
Number (#) of particles Increasing the number of particles will increase the pressure of a gas while temperature and volume are constant. Ex.) blowing up a balloon Ex.) inflating a tire/inner tube
Charles Law French Physicist, Jacques Charles (1746-1823) Invented the hydrogen balloon Absolute zero, 0K(Kelvin) not been produced in a lab The volume of a gas is directly proportional to its temperature in kelvins if the pressure and the number of particles is constant. V1/T1 = V2/T2 Temperature MUST be in Kelvins
Boyle s Law Robert Boyle, Ireland Described the relationship between pressure and volume of a gas The volume of a gas is inversely proportional to its pressure if the temperature and number of particles remains constant. P 1V 1 = P 2V 2
The Combined Gas Law When the number of particles are constant: P1V1/T1 = P2V2/T2
3.3 Phase Changes Phase change Endothermic Heat of fusion Exothermic Vaporization Heat of vaporization Evaporation Vapor pressure Condensation Sublimation deposition
Key Concepts What are six common phase changes? What happens to a substance s temperature and a system s energy during a phase change? How does the arrangement of water molecules change during melting and freezing? How are evaporation and boiling different?
Characteristics of Phase Changes Phase change reversible All phase changes share certain characteristics related to energy and temperature. Melting, freezing, vaporization, condensation, sublimation, deposition
Temperature and Phase Change The temperature of a substance does NOT change during a phase change.
Energy and Phase Change Energy is either absorbed or released during a phase change. Endothermic change absorbs energy Amount of energy absorbed depends on the substance heat of fusion (another term for melting) Exothermic change releases energy
Melting and Freezing The arrangement of molecules in water becomes less orderly as water melts and more orderly as water freezes. Melting point of water 0 degrees Celsius, 32 degree Fahrenheit
Melting As ice gains energy (solid), the molecules vibrate more quickly when the molecules gain enough energy to move from their fixed positions the melting point is reached Melting point of water is 0 degrees Celsius or 32 degrees Fahrenheit Energy gained increases the average kinetic energy which increases temperature
Freezing Opposite of melting As the average kinetic energy is reduced molecules become more fixed
Vaporization and Condensation