Molecular Motion Chapter 3

Matter and Energy Matter- anything that has mass and volume 4 states: solids, liquids, gases, plasma Energy- ability to do work: Potential Kinetic

Kinetic Molecular Theory Kinetic Molecular Theory (KMT): All matter is made of constantly moving particles (atoms, molecules) All particles have kinetic energy (KE)

Temperature and Kinetic Energy measure of average kinetic energy the more KE an object has, the higher its temperature Thermal energy= total KE; depends on: particle speed- faster particles have more KE number of particles- more particles have greater thermal energy

Energy and Solids Solids low KE - particles vibrate but can’t move around definite shape, volume: *crystalline - repeating geometric pattern *amorphous - no pattern (e.g. glass, wax)

Energy and Liquids Liquids higher KE - particles can move, but are still close together indefinite shape, not volume flows-fluid

Energy and Gases Gases high KE – particles move freely indefinite shape and volume flows- fluid

Energy and Plasma Plasma very high KE- particles collide with enough energy to ionize (break into charged particles) lacks definite shape or volume can conduct electric current (unlike gases) most common state of matter

States of Matter Matter Shape Volume Solids Definite Liquids Not definite Gases

Changes of States Requiring Energy (Remember: heated particles move faster; cool particles move slower Melting point- solid to liquid Evaporation- liquid to gas Sublimation- solids to gas

Changes of State Releasing Energy Condensation- gas to liquid Freezing- liquid to solid Temperature is constant during all changes in state of matter (ex: If energy is added to ice, the temperature of ice will not rise until all the ice has melted)

Conservation of Matter and Energy Neither mass nor energy can be created or destroyed during changes of state

Pressure and Fluids Fluids: (liquids, gases) exert pressure evenly in all directions Pressure: amount of force exerted on a given surface Pressure = force area Pascal (Pa): unit of pressure; 1N/m²

Buoyant Force * bouyant force > weight object rises Buoyant force: the ability of a fluid to exert an upward force on an object immersed in it (forces pushing up > forces pushing down) * bouyant force > weight object rises ** bouyant force < weight object sinks ***bouyant force = weight object floats

Buoyancy and Density Density: = mass ÷ volume; D= m v An object with D less than 1 g/cm³ will float

Archimedes Principle Archimedes principle: the bouyant force on an object in a fluid is equal to the weight of fluid displaced by the object

Pascal’s Principle Pascal’s Principle: a change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of the fluid F₁ = F₂ A₁ A₂

Pascal’s Principle Hydraulic devices: use liquid to transmit pressure from one point to another ex: hydraulic breaks in cars, movement in starfish

Pascal’s Principle Practice A car weighing 1000 N sits on a 250 m2 platform. What force is needed on the 10 m2 plunger to keep the car from sinking? Given: Platform: F= 1000 A= 250m² Plunger: F= ? A= 10m² Remember: F₁ = F₂ A₁ A₂ Solve: 1000 N= F₂ 250m² 10m² (1000N)(10m²)=(250m²)F₂ F₂ = 40N

Bernoulli’s Principle Bernoulli’s Principle: as the velocity of a fluid increases, the pressure exerted by the fluid decreases

Bernoulli’s Principle Viscosity: a fluid’s resistance to flow (usually, the stronger the attraction between particles in a liquid, the slower it flows)

Bernoulli’s Principle Venturi Effect: fluids flow faster through narrow spaces causing reduced pressure