Chapter 4A: Physical Behavior of Matter

Aim: To examine the solid, liquid, and gaseous phases of matter To learn how to calculate the heat exchanged during heating, cooling, and phase changes

Phases of Matter An element, compound, or mixture may exist in 3 different forms. They may be in: Solid Liquid Gas

What Defines a Solid Held in a rigid form Definite shape and volume VERY STRONG attractive forces Definite shape and volume Particles in fixed positions Can vibrate but not move Crystalline structure

What Defines a Liquid? Not as rigid Definite volume, but takes the shape of the container Sufficient attractiveness to have a definite volume Particles are close to each other and can slide past each other No regular pattern or arrangement of particles

What Defines a Gas? No definite volume and no definite shape Minimal attractive forces Particles are very far apart Gases spread out indefinitely Fill the volume of the container Vapor is a gaseous form of a substance that is normally a liquid or solid form

Heating Curves http://www.kentchemistry.com/links/Matter/HeatingCurve.htm

A few Definitions: Temperature- measure of the average KINETIC ENERGY of a substance Kinetic Energy- “moving” energy So, increasing the temperature means you are increasing the movement of the particles Potential Energy- stored energy So, phase changes Heat of Fusion- amount of heat required to convert a solid to a liquid Melting (fusion) is the reverse of freezing Heat of Vaporization- amount of heat required to convert a liquid to a gas Vaporization is the reverse of condensation

Heating Curves Either the temperature is changing or the phase is changing. NOT BOTH What Happens: Ice is absorbing kinetic energy so temp is rising Ice is melting. The potential energy increases because the heat is being used to break the bonds and cause the phase change. Heat of Fusion. Water is absorbing kinetic energy so temp is rising Water is boiling. The potential energy increases because the heat is being used to break the bonds and cause the phase change. Heat of Vaporization. Gas is absorbing kinetic energy so temp is rising As you go up, energy is absorbed. (It feels HOT) As you go down, energy is released. (It feels COOL)

Heating Curves So, as the graph is going up, the temperature is changing The heat being added is adding to the average kinetic energy (temperature) But, the phase stays the same As the graph plateaus, the phase is changing The heat being added is melting the ice/ vaporizing the liquid (phase change) But, the temperature is staying the same

Heating Curves As the graph goes up, it is ENDOTHERMIC because it is absorbing energy As the graph goes down, it is EXOTHERMIC because it is releasing energy

Special Circumstances Sublimation: When a solid phase changes to a gas and skips the liquid phase CO2(s) Dry Ice Deposition Formation of frost

Open your workbook to p. 60 (1-16) 4- solid 1- only solid 1- gas 2 2- gas 3- solid 3- s => g 2- s => g 1- all water 2 3- B => E 4 1 4- going up 2- going down

Energy Defined as the ability to do work Measured in Joules (J) Table T and Table B There are many different forms of energy Energy cannot be created nor destroyed, but can be converted from one form to another

What are some types of energy? Chemical Released or absorbed in a chemical reaction Electrical Flow of electrons Electromagnetic Radiation Energy made up of waves Mechanical Energy of moving objects Nuclear Energy given off when a nucleus breaks up into smaller nuclei or vice versa Heat (thermal) Random motion of atoms and molecules

What is Thermal Energy? Heat Energy Heat always flows from hotter body to the cooler body It flows from the object that has MORE energy to the object that has LESS energy From the HURT LEG to the ICE PACK From the WATER to the ICE in the glass

Temperature Measured with a thermometer Measure of the average kinetic energy of the molecules More movement = higher temperature More movement = more space between the particles Solids- particles are next to each other, touching Gases- particles are spread out Units are Celsius (oC) and Kelvin (K) Kelvin = Celsius + 273 (Table T) Direct scaled between them. So, an increase of 5oC is an increase of 5K

Convert the following: 0oC to Kelvin 0K to Celsius -10oC to Kelvin 300K to Celsius

Open your workbook to p. 63 (17-29) 4 1 3 1 3 3 (increase of 10o)

Measurement of Heat Energy Amount of heat given off or absorbed in a reaction Table T and Table B Calorimeter q = mCDT q = ? m = ? C = ? D = ? T = ?

Let’s Do an Example… A 7.00 gram sample of water is heated and the temperature rises from 10.0oC to 15.0oC. What is the total amount of heat energy absorbed by the water? q = ? m = ? C = ? T1 = ? T2 = ? D = ?

Answer q = mCDT q = ? m = 7.00 grams C = 4.18 J/g * oC T1 = 15.0 T2 = 10.0 oC D = 5.0 oC q = (7.00g) (4.18 J/g * oC) (5.0oC) q = 146 J

One More Example… The temperature of 15.00 grams of water was increased by 3.00oC. How much heat energy was absorbed by the water? q = ? m = ? C = ? T1 = ? T2 = ? D = ?

Answer q = mCDT q = ? m = 15.00 grams C = 4.18 J/g * oC T1 = ? T2 = ? D = 3.00 oC q = (15.00g) (4.18 J/g * oC) (3.00oC) q = 188 J

Heat of Fusion q = mHf Table T Amount of heat required to convert a unit of mass from a solid to a liquid (or a liquid to a solid) For solid water at 0oC and 1atm is 334J/g Table B Increases the potential energy without increasing the kinetic energy So, remember, no change in temperature!

Heat of Vaporization q = mHv Table T Amount of heat required to convert a unit of mass from a liquid to a gas (or a gas to a liquid) For solid water at 100oC and 1atm is 2260J/g Table B Increases the potential energy without increasing the kinetic energy So, remember, no change in temperature!

Let’s do an Example q = mHf How many joules are required to melt 255g of ice at 0oC?

Let’s do an Example q = mHv How many joules of energy are required to vaporize 423g of water at 100oC and 1atm?

Open your book to p. 65-66 (30-46) D d D d

STUDY for your TEST!!!!