Solids, Liquids, and Gases States of Matter Solids, Liquids, and Gases Y:\HSMedia\Science\Integrated Science Video folder\Physical_Science__States_of_Matter.asf

Describing State of Matter Solids State of matter in which materials have a definite shape and a definite volume Liquid State of matter in which a material has a definite volume but not a definite shape Takes on the shape of the container it is in Gas State of matter in which in which a material has neither a definite shape nor a definite volume

Other State of Matter 99% of all the matter in the universe exists in a state of matter that doesn’t exist here on Earth Plasma Extremely high temperature (Stars) Bose-Einstein Condensate (a 5th state of matter Extremely low temperatures near absolute zero

Plasma and Bose-Einstein Condensate

Kinetic Theory Kinetic energy – the energy due to motion Word comes from the Greek word meaning “to move” The faster an object moves the greater its kinetic energy Kinetic Theory States that all particles of matter are in constant motion

Explaining the Behavior of Gases Particles in a gas are never at rest At room temperature Average speed is about 1600 km/hr Particles are constantly colliding with one another There are also other forces of attraction among all particles of matter If particles are moving fast this attraction is fairly weak In gases these forces can be ignored

Kinetic Theory of Gases The constant motion of particle in a gas allows a gas to fill a container of any shape or size Particles in a gas are in constant random motion The motion of one particle is unaffected by the motion of other particles unless the particles collide Forces of attraction among particles in a gas can be ignored under ordinary conditions

Explaining the Behavior of Liquids Particles tend to have a lower average kinetic energy Particles are more closely packed together than those in a gas The attraction between particles does have an influence in liquids A liquid takes the shape of its container because particles in a liquid can flow to new locations The volume of a liquid is constant because forces of attraction keep the particles close together

Explaining the behavior of solids Solids have a definite volume and shape because particles in a solid vibrate around fixed locations Vibrations tend to be in a back and forth motion Atoms much closer together Atoms are kept in a fixed location

The Gas Laws Section 3.2

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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?

When we breathe When you inhale, the volume of y our chest cavity increases and air moved into you lungs When you exhale, the volume of your chest decreases and air is pushed out of your lungs

Pressure Pressure – the result of force distributed over an area Force is measured in newtons (N) and area in square meters (m2) The unit of force becomes N/m2 We shorten this to an SI unit called a pascal (Pa) Often expressed as kilopascals (kPa) or 1000 pascals It is the collisions between particles of a gas and the walls of the container that cause the pressure in a closed container of gas

Factors that affect Gas Pressure Collisions between particles of a gas and the walls of the container cause pressure in a closed container of gas Factors that affect the pressure of a gas in an enclosed container are temperature, volume, and number particles

Temperature Raising the temperature of a gas will increase the pressure if the volume of the gas and the number of particles remains the same Can on a fire

Volume Reducing the volume of a gas in an enclosed container increases its pressure if the temperature of the gas and the number of particles remain the same Breathing

Number of particles Increasing the number of particles will increase the pressure of a gas if the temperature and volume are constant Airing up a tire

Factor Affecting Gas Pressure Temperature Raising the temperature of a gas will increase its pressure if the volume of the gas and the number of particles are constant Volume Reducing the volume of a gas increases its pressure if the temperature of the gas and the number of particles are constant Number of Particles Increasing the number of particles will increase the pressure of a gas if the temperature and the volume are constant

Boyles’ Law The volume of a gas is inversely proportional to its pressure if the temperature and the number of particles are constant

Boyle’s Law Boyle’s Law states that the volume of a gas is inversely proportional to its pressure if the temperature and the number of particles are constant. Pressure can be expressed as Atmospheres, pascals (Pa), kilopascals kPa), mm of Hg Put in mathematical terms P1V1 = P2V2 P1 = Initial Pressure V1 = Initial Volume P2 = New Pressure V2 = New Volume

P1V1 = P2V2 P1 = Initial Pressure V1 = Initial Volume P2 = New Pressure V2 = New Volume P1= P2V2 / V1 V1 = P2V2 / P1 P2= P1V1 / V2 V2 = P1V1 / P2

Problem with Boyle’s Law We have 200L of gas under 200 kPa of pressure. If we increase the pressure to 800kPA, what is the new volume of gas? V2 = P1V1/P2 P1 = 200 kPa V1 = 200 L P2 = 800 kPa V2 = (200kPA)(200L)/800kPa = 50 L

Charles Law The volume of a gas is directly proportional to its temperature in Kelvin's if the pressure and number of particles remain the same

Charles’s Law Charles’s Law – states that the volume of a gas is directly proportional to its temperature in kelvins if the pressure and the number of particles of the gas are constant Put in mathematical terms (Temperature must be in kelvins) V1/T1 = V2/T2 V1 = initial volume T1 = initial temperature (K) V2 = new volume T2 = new temperature Let’s rearrange the formula to solve for all 4 terms

Problem with Charles’s Law We have a 5 L of gas at 25ºC. We raise the temperature to 50ºC. What is the new volume of the gas? Rearranging the formula V2 = (V1/T1)(T2) V1 = 5 L T1 = 298 K (25ºC +273) T2 = 323K (5L/298K)(323K) = 5.42 L

Gay Lussac’s Law When temperature increases, pressure increases if the volume is kept constant P1/T1 = P2/T2 P1 = (P2/T2)(T1) T1= (T2/P2)(P1) P2 = (P1/T1)(T 2) T2 = (T1/P1)(P2) This is also a direct proportion so the line on the graph would be a straight line

Gay Lussac’s Law We have a gas under 6 atmospheres of pressure and a temperature of 300 K. If we increase the pressure to 10 atmospheres, what will the new temperature of the gas be?

Combined Gas Law The Combined Gas Law describes the relationship among temperature, volume, and pressure of a gas when the number of particles is constant Putting it in mathematical terms P1V1/T1 = P2V2/T2

Phase Changes Chapter 3 Section 3

Characteristics of Phase Changes If a substance can exist in 2 or more states then those states are called phases Phase Change: the reversible physical change that occurs when a substance changes from one state of matter to another. Common phase changes: melting, freezing, vaporization, condensation, sublimation, and deposition

Releases energy = Exothermic Absorbs energy = Endothermic

Temperature and Phase Change The temperature of a substance does not change during a phase change

Energy and Phase Changes During a phase change, energy is transferred between a substance and its surroundings – energy is either released or absorbed during a phase change Endothermic: Energy is absorbed from the surroundings The amount of energy absorbed with vary from substance from substance

Energy and Phase Changes Heat of fusion: the amount of energy a substance needs to absorb to melt The heat of fusion will vary from substance to substance Water = 79.72 calories/gram or 334.5 kilojoules/kilogram Propane = 19.11 calories/gram or 79.96 kilojoules/kilogram Acetic Acid (Vinegar) = 45.91 calories/gram or 192.09 kilojoules/kilogram

Energy and Phase Changes Exothermic: when the system releases energy to the surroundings – water freezing When water freezes it releases 334 joules of energy to its surroundings for every gram of water Why would farmers spray water on their plants to protect them in freezing weather?

Melting The arrangement of the molecules in water become more orderly as water freezes and less orderly as ice melts In ice the attraction between the water molecules keeps them in a fixed position Melting: heat flows from the air to the ice Molecules begin to move more quickly and can move from their fixed position When all the molecules have enough energy to move melting is complete

Freezing Energy flows from the water to the air as the water cools down Molecular motion decreases and the attraction between the water molecules allows them to arrangement themselves in fixed positions Does freezing mean cold?

Vaporization Vaporization: phase change from a liquid into a gas Endothermic 1 g of water gains 2261 joules of energy when it vaporizes – called Heat of vaporization Heat of vaporization varies from substance to substance Two processes: boiling and evaporation Evaporation takes place at the surface and at a temperature below the boiling point

Evaporation Evaporation: the process that changes a substance from a liquid to a gas at temperatures below the substance’s boiling point The greater the surface area = the greater the evaporation rate Vapor Pressure: in a closed container the pressure caused by the collisions of vapor with the walls of the container. Vapor pressure increases as temperature increases.

Boiling Takes place when vapor pressure = atmospheric pressure Molecules are moving faster and eventually overcome their attraction for each other Boiling point depends on atmospheric pressure What happens to the boiling point at higher altitudes? – What does that mean for cooking?

Condensation Condensation: the phase change in which a substance changes from a gas or vapor into a liquid Exothermic

Sublimation Sublimation: Phase change in which a substance changes from a solid to a gas or vapor without changing to a liquid first Endothermic Dry Ice The reverse of deposition

Deposition Deposition: when a gas or vapor changes directly into a solid without first changing to a liquid Exothermic The reverse of sublimation Frost