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 substance’s 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

Pascal’s 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 liquid’s resistance to flow

Bernoulli’s 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 Boyle’s 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 gas’s pressure decreases –Likewise, the volume of a gas decreases as the gas’s pressure increases –P 1 V 1 = P 2 V 2

Gas Laws Gay-Lussac’s 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 Charles’s Law –For a fixed amount of gas at a constant pressure, the volume of the gas increases as the gas’s temperature increases –Likewise, the volume of the gas decreases as the gas’s temperature decreases –V 1 /T 1 = V 2 /T 2