Chapter 3 States of Matter Matter and Energy Kinetic Theory: matter is made of atoms and molecules and these atoms and molecules act like tiny particles that are always in motion The higher the temperature the substance is, the faster the particles move. The cooler the slower the particles move. At the same temperature, more massive particles move slower than less massive ones. States of Matter Solids: have a definite shape and volume Particles cannot easily move Particles held together by strong attractions, and vibrate in place States of Matter Liquids: change shape, not volume Particles move more rapidly than in a solid but not as rapidly in a gas Particles move fast enough to overcome some of the forces of attraction between them Take the shape of their container States of Matter Gases: change both shape and volume Do not have fixed shapes Because the particles in liquids and gases can move past each other, liquids and gases are fluids States of Matter Plasma is the most common state of matter Does not have a definite shape or volume Particles are electrically charged, or ionized Lightning, fire, and aurora borealis, fluorescent lights Properties similar to gases but have some properties that are different from the properties of gases Plasmas conduct electric current, while gases do not Energy The ability to change or move matter, or to do work Kinetic energy: the energy of motion Temperature is a measure of the average kinetic energy of the particles in an object (how hot or cold something is) The more kinetic energy the particles of an object have, the higher the temperature of the object Thermal energy is the total kinetic energy of a substances atoms Depends on the number of particles in that substance Changes of State The identity of a substance does not change during a change of state, but the energy of a substance does change A transfer of energy known as heat causes the temperature of a substance to change Changes of State Evaporation: change of a substance from a liquid to a gas Boiling is evaporation that occurs throughout a liquid at a specific temperature and pressure (boiling point) Sublimation: solids can also change directly into gas Snow/dry ice/ice cubes in a freezer Changes of State Condensation: water vapor in the air becomes a liquid Energy is released Freezing: liquid to a solid Energy is released Same as melting point Changes of State Temperature is constant during changes of state Law of Conservation of Matter/Energy Mass is conserved for all physical and chemical changes Energy can change forms during physical and chemical changes, but the total amount of energy present before and after a change is the same Neither mass nor energy can be created or destroyed Fluids Pressure is the amount of force exerted on a given area of surface Fluids (gas/liquids) exert pressure evenly in all directions Pressure = Force / Area (P = F / A) The SI unit of pressure is the pascal One pascal (Pa) is the force of one newton exerted over an area of one square meter (1 N/m 2 ) Buoyant Force All fluids exert an upward buoyant force on matter Buoyant force results from the fact that pressure increases with depth The forces pushing up on an object in a fluid are greater than the forces pushing it down Thus, there is a net upward force (BUOYANT FORCE) Archimedes Principle The buoyant force on an object in a fluid is an upward force equal to the weight of the fluid that the object displaces Floating Based on density Water density is 1.00 g/cm 3 Greater: sink / less: float Pascals Principle A change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of the fluid The pressure in a container is increased at any point, the pressure increases at all points by the same amount P 1 = P 2 (P = F / A) F 1 / A 1 = F 2 / A 2 Toothpaste tube / hydraulic devices (multiplies the force) / power brakes / power steering Fluids in Motion Fluids move faster through small areas than through larger areas, if the overall flow rate remains constant Fluids also vary in the rate at which they flow Viscosity: a liquids resistance to flow Bernoullis Principle States that as the speed of a moving fluid increases, the pressure of the moving fluid decreases Large (circumference) pipe (water slower) connected to smaller (circumference) pipe (water faster) Wing of airplane: Air flows over the top faster (lower pressure) than the bottom of the wing (higher pressure) Behavior of Gases Gases expand to fill their containers and exert pressure on their containers They spread out easily and mix with one another They have low densities and are compressible Unlike solids and liquids, gases are mostly empty space Gas Laws Boyles Law Relates the pressure of a gas to its volume For a fixed amount of gas at a constant temperature, the volume of a gas increases as the gass pressure decreases Likewise, the volume of a gas decreases as the gass pressure increases P 1 V 1 = P 2 V 2 Gas Laws Gay-Lussacs Law The pressure of a gas increases as the temperature increases, if the volume of the gas does not change (constant) The pressure decreases as the temperature decreases P 1 / T 1 = P 2 / T 2 Gas Laws Charless Law For a fixed amount of gas at a constant pressure, the volume of the gas increases as the gass temperature increases Likewise, the volume of the gas decreases as the gass temperature decreases V 1 /T 1 = V 2 /T 2