Chapter 14: Solids, Liquids, and Gases Section 1: Matter and Thermal Energy Section 2: Properties of Fluids Section 3: Behavior of Gases

Section 1: Matter and Thermal Energy States of matter Kinetic Theory – an explanation of how particles in matter behave 4 assumptions: all matter is composed of small particles the particles are in constant, random motion these particles are colliding with each other and the walls of their container the amount of energy that the particles lose from these collisions is negligible Thermal energy – the total energy of a material’s particles Includes KE – the motion of the particles Includes PE – the force that acts within or between particles Average KE – a measure of the hotness or coldness or a material (temperature) Thermal expansion – the increase in the size of a substance when the temperature of the substance is increased Expansion and contraction can occur in most solids, liquids, and gases Water is the exception to thermal expansion Water expands when it changes state from a liquid to a solid

Section 1: Matter and Thermal Energy States of matter The four states of matter: Solid – has a definite volume and definite shape particles are closely packed together most solids have a specific geometric arrangement Liquid – has a definite volume and assumes the shape of its container particles in the material slide past one another (flow) the attractive force between particles is less particles have higher KE than those in a solid melting point: the temp. at which a solid begins to liquefy heat of fusion: the amount of energy required to change a substance from the solid phase to the liquid phase Gas – no definite volume or shape particles of a substance are moving very fast no attractive force between the particles boiling point: the temp. at which the pressure of a vapor is equal to the pressure of the atmosphere heat of vaporization: the amount of energy required for the particles to overcome the attractive forces within the liquid (energy required to change from a liquid to a gas) Plasma - a gas consisting of positively and negatively charged particles 99% of the matter of in the universe is in this state all the stars are plasma, as are lighting bolts and auroras

Section 2: Properties of Fluids A fluid is any material that flows – liquids and gases are fluids  Buoyancy – the ability of a fluid to exert an upward force on an object immersed in the fluid Archimedes Principle – the buoyant force on an object is equal to the weight of the fluid displaced by the object, or: Example 1: A piece of glass, its volume = 0.05-m3, is placed in a container of seawater. What is the buoyant force acting on the piece of glass Solution Where: FB = buoyant force (N) ρ = density (kg/m3) V = volume (m3) g = acceleration due to gravity (9.8 m/s2)

Section 2: Properties of Fluids Example 2: Will the glass from example 1 float in the seawater or will it sink? Look at the graphic to the right . Notice the two forces acting on the piece of glass. If we can calculate the weight of the piece of glass we can then compare it to the buoyant force acting on the glass. If the weight is greater than the buoyant force it will sink, if the weight is less it will float. Here is a new equation for weight: Solution FB = 502.25-N, W = 1,274-N. The glass will sink 𝑾=𝝆𝑽𝒈 Where: Ρ = the density of the object immersed in the fluid V = the volume of the object g = acceleration due to gravity (9.8m/s2)

Section 2: Properties of Fluids Pascal’s Principle – pressure applied to a fluid travels through the fluid Pressure – force per unit volume Hydraulics – the use of pressure in fluids to do work Hydraulic lift – a machine that moves heavy loads in accordance with Pascal’s Principle Example: a car lift at a garage A pipe filled with fluid connects a cylinder with a small diameter to a cylinder with a large diameter 1) pressure is applied to the small cylinder and is transferred through the fluid 2) because the pressure remains constant throughout the fluid, more force is available in the larger cylinder Example: a hydraulic lift applies a force of 2,500-N to a piston with an area of 5-m2. The resulting pressure is transferred to a cylinder with a 7.5-m2 piston. What is the force acting on the 2nd piston? Solution

Section 3: Behavior of Gases Pressure Gas particles are constantly moving and colliding with anything in their path The collision of gas molecules in air result in atmospheric pressure Pressure – the amount of force exerted per unit area, or: Pressure is measured in units pascals (Pa) 1-Pa = 1n/m2 → a very small unit Most pressures are expressed as kilopascals (kPa) At Earth’s surface (sea level) pressure = 101.3kPa In containers (ex.: a tire) the gas molecules collide with the container’s wall resulting in pressure being applied to the walls

Section 3: Behavior of Gases The Gas Laws Boyle’s Law – at constant temperature, a change in volume results in a change in the pressure on the container As volume decreases, pressure increases As volume increase, pressure decreases At constant temperature, the product of pressure and volume is constant, or: So: Example: A balloon has a volume of 10.0-L at a pressure of 101-kPa. What will the volume be if the pressure drops to 43-kPa? Solution

Section 3: Behavior of Gases The Gas Laws Charles’s Law – at constant pressure, the volume of a gas increases as the temperature increases Mathematically: Example: At 293 K the volume of an inflated balloon is 5-L. Two hours later the temperature is 305 K, what is the balloon’s volume now? Solution

Section 3: Behavior of Gases The Gas Laws Guy-Lussac’s Law – At constant volume, the pressure exerted by the gas increases as temperature increases Mathematically: Example: At 293 K the pressure of the gas in an aerosol can is 150 kPa. What is the pressure in the can when the temperature is 310 K? Solution