Solids, Liquids, and gases

Kinetic theory explanation of the behavior of particles in gases: 1. gas is made of tiny particles 2. particles are in constant, random motion 3. collisions between particles are elastic-- no kinetic energy lost

temperature Measure of the average kinetic energy of particles that make up a substance. Kinetic Energy: energy of motion. Faster movement, more KE

gas Substance made of quickly-moving, mostly non-interacting particles fills up the volume and shape of a container holding it.

Liquid Substances made of interacting particles that has a constant volume and takes the shape of its container. Have less kinetic energy than particles that are gases.

solid Substance made of closely packed particles that have a definite shape and volume. Lower kinetic energy of the particles occurs as vibrations.

plasma the fourth state of matter consisting of particles with kinetic energy high enough such that electrons are stripped off of atoms Most of the matter in the universe is in this state.

Melting point temperature at which a solid begins to liquefy. Water: 0°C At this temperature particles have the kinetic energy to break free from tighter interactions of the solid state

Heat of fusion amount of energy required to change a substance from the solid phase to the liquid phase. Any energy absorbed by the solid goes to phase change, and NOT temperature change.

Boiling point the temperature at which the pressure of vapor of a liquid is equal to the external pressure acting on the surface of the liquid. 100°C for water. Vapor pressure is how much force per area particles exert on their surroundings. Increased temperatureincreased K.E.increased vapor pressure

Heat of vaporization amount of energy required for a liquid at its boiling point to become a gas. Water may reach 100°C and not boil. MORE energy is needed to give particles enough K.E. to escape interactions Boiling fluid will remain at the boiling point temp until all particles are in gas state

Melting curve

Think: What would happen to the boiling point of water if the atmospheric pressure were lowered? Hint: look at boiling point definition Turn and Talk Share

sublimation the process of a solid changing directly to a vapor without forming a liquid.

Density How much matter (mass) is contained within a given space (volume) OR, density = mass/volume ρ = m/V

Density Generally, a solid is more dense than a liquid, which is more dense than a gas Water is an exception: ice is less dense than liquid water Density of water = 1 g/mL (exactly) at 4°C.

Thermal expansion increase in the volume of a substance when the temperature is increased Density decreases

Density practice problems Pure solid gold has a density of 19.32 g/cm3. What is the mass of a cubic meter (or 1,000,000 cm3) of gold? What is the density of ice if 5.33 cm3 of ice has a mass of 4.886 g?

Amorphous solids solids lacking a crystalline structure that do not have a specific melting point Examples: Butter, solid grease, petroleum jelly

buoyancy ability of a fluid (liquid or gas) to exert an upward force on an object immersed in it.

Archimede’s principle the buoyant force on an object is equal to the weight (gravitational force) of the fluid displaced by the object. Gravitational force If object’s density > fluid density, it sinks. object’s density < fluid density, it floats

If an object is floating… Weight of object (gravitational force) is balanced with the opposing weight of the water displaced (buoyant force) Weight of object = weight of water displaced Use the density equation to convert from volume of water displaced to mass/weight of water displaced.

Why do we float in the dead sea?

Archimedes' principle practice A man is floating in water. The buoyant force acting on his body is 210 lbs (pounds are a unit of force). What is the man’s weight? A river barge weighs 5,340 N. What is the weight of the water it displaces when it floats? A floating object displaces 10.0 cubic feet (ft3) of water. How much does the object weigh if the weight density of water is 62.43 lbs/ft3?

Pressure amount of force exerted per unit area.

Units of force Newtons (N) and pounds (lbs)

𝐹𝑖𝑛 𝐴𝑖𝑛 = 𝐹𝑜𝑢𝑡 𝐴𝑜𝑢𝑡 Pascal’s principle Pin = Pout the pressure applied to one part of a fluid is transmitted throughout it. Ex: squeezing toothpaste Pin = Pout 𝐹𝑖𝑛 𝐴𝑖𝑛 = 𝐹𝑜𝑢𝑡 𝐴𝑜𝑢𝑡

Bernoulli’s principle as the velocity of a fluid increases, the pressure exerted by that fluid decreases. Higher pressure

Boyle’s Law at a constant temperature, pressure and volume of a gas are inversely related. 𝑃1𝑉1=𝑃2𝑉2 Example: squeezing a balloon until it pops

Kelvin (units) units of temperature equal in magnitude to Celsius, that begin (zero value) at -273.15 C. 0 K is called absolute zero. NO kinetic energy.

Charles’ law at a constant pressure, the volume of a gas increases with increasing temperature. 𝑉1 𝑇1 = 𝑉2 𝑇2 Examples: Hot air balloon, car tires in cold weather