States of Matter Chapter 10

Kinetic Theory Kinetic refers to motion. Kinetic refers to motion. Kinetic energy is the energy of a moving object. Kinetic energy is the energy of a moving object. Kinetic theory states that the tiny particles in all forms of matter are in constant motion. Kinetic theory states that the tiny particles in all forms of matter are in constant motion.

1. A gas is composed of small particles that have no attractive or repulsive forces between them. 2. Move in constant random motion, but in straight paths.(Gases fill their containers regardless of shape or volume. Uncontained gases diffuse into space with out limit.) 3. During collisions kinetic energy is transferred without loss from one particle to another.

Gas Pressure Defined as the force exerted by a gas per unit surface area of an object. Defined as the force exerted by a gas per unit surface area of an object. Vacuum – empty space, no pressure (outer space) Vacuum – empty space, no pressure (outer space) Air exerts pressure on earth because of gravity. Air exerts pressure on earth because of gravity. Air pressure increases the higher you go. Air pressure increases the higher you go.

The SI unit of pressure is the pascal (Pa). The SI unit of pressure is the pascal (Pa). mmHg & atmosphere (atm) are other units of pressure. mmHg & atmosphere (atm) are other units of pressure. 1 atm = 760 mmHg = kPa 1 atm = 760 mmHg = kPa

Kinetic Energy & Temperature When particles are heated they speed up therefore increasing temperature. When particles are heated they speed up therefore increasing temperature.

Graphs Horizontal axis (x-axis) represents the independent variable. Horizontal axis (x-axis) represents the independent variable. Vertical axis (y-axis) represents the dependent variable. Vertical axis (y-axis) represents the dependent variable. Range is the minimum and maximum values represented in the graph. Range is the minimum and maximum values represented in the graph.

Making Graphs 1. Choose appropriate ranges 2. The intervals should be convenient numbers (1, 5, 10) 3. Draw and label axis 4. Plot data 5. Connect data with smooth curve. (does not have to touch all data points)

Nature of Liquids Liquids: 1. Particles that make up liquids are in motion. 2. Particles have an attractive force between them, but able to move. 3. This force is called intermolecular force.

Evaporation: conversion to a gas from a liquid that is not boiling conversion to a gas from a liquid that is not boiling 1. Vaporization: transition of a liquid to gas 2. When heat is added vaporization occurs faster. 3. Liquid – vapor (gas)

Boiling Points: The temperature at which the vapor pressure of liquid is just equal to the external pressure. 1. Boiling points change when external pressures change. (less pressure = lower boiling points) 2. The temperature of a boiling liquid never rises above its boiling point.

Nature of Solids Solids: 1. Particles are in fixed points; tend to vibrate in their spots. 2. Particles tend to be in highly organized patterns. 3. Melting point – the temperature at which the solid melts

4. As heat is added the organization of particles begins to break down and solid melts. 5. Melting: Solid – liquid Freezing: Liquid – solid 6. Not all solids melt; some decompose

Crystal Structures The atoms, molecules or ions are arranged in an orderly, repeating 3-D pattern. The atoms, molecules or ions are arranged in an orderly, repeating 3-D pattern. Unit Cell: smallest group of particles within a crystal; repeating group Unit Cell: smallest group of particles within a crystal; repeating group (simple cubic, body centered cubic & facecentered cubic).

Crystal Structures 1. All crystals have a regular shape. 2. Crystals have sides or faces. 3. Crystals are classified in 7 groups

Allotropes: Two or more different molecular forms of the same element in the same physical state. Two or more different molecular forms of the same element in the same physical state. Ex. Carbon --- diamond - graphite Ex. Carbon --- diamond - graphite

Amorphous Solids: Lack an ordered internal structure Lack an ordered internal structure Examples: Rubber, plastic, asphalt Examples: Rubber, plastic, asphalt Particles are randomly arranged. Particles are randomly arranged.

Change of State Phase Diagram: gives the conditions of temperature & pressure at which a substance exists as a solid, liquid, & gas. Phase Diagram: gives the conditions of temperature & pressure at which a substance exists as a solid, liquid, & gas. Triple Point: a set of conditions at which all three states can exist with one another. Triple Point: a set of conditions at which all three states can exist with one another.

Sublimation: the change of a substance from a solid to a vapor without passing through the liquid state. Sublimation: the change of a substance from a solid to a vapor without passing through the liquid state.Examples: Solid carbon dioxide (dry ice) Moth balls Moth balls

Add to Gas Pressure: Barometers: devices commonly used to measure atmospheric pressure. This pressure depends on the weather. Barometers: devices commonly used to measure atmospheric pressure. This pressure depends on the weather.

Gas Laws Chapter 12

The SI unit of pressure is the pascal (Pa). The SI unit of pressure is the pascal (Pa). mmHg & atmosphere (atm) are other units of pressure. mmHg & atmosphere (atm) are other units of pressure. 1 atm = 760 mmHg = kPa 1 atm = 760 mmHg = kPa REMEMBER:

Properties of Gases Compressibility: measure of how much the volume of matter decreases under pressure. Compressibility: measure of how much the volume of matter decreases under pressure. 1. Gases are easily compressed. 2. Gases expand to take the shape & volume of the container. 3. Gas particles are in constant motion.

Variables that describe Gases 1. Pressure (P) in kPa 2. Volume (V) in L 3. Temperature (T) in K 4. Moles (n)

Gas Pressure 1. Increase the # of gas particles; increases the gas pressure 2. Doubling the # of gas particles; doubles the pressure. 3. Once the pressure exceeds the strength of the container the container will rupture. (Direct Relationship)

4. If you let gas out. Then the pressure drops. 5. When a sealed container of gas under pressure is opened. Gas inside moves from the region of higher pressure to the region of lower pressure.

Volume: raise the pressure exerted by contained gas by reducing its volume. Volume: raise the pressure exerted by contained gas by reducing its volume. (Inverse Relationship)

Temperature: Temperature: 1. Raising the temperature of an enclosed gas increases gas pressure. 2. If the temperature doubles then the pressure doubles. (Direct Relationship)

Standard Temperature & Pressure (STP) Temperature – 273 K Temperature – 273 K Volume – 22.4 L Volume – 22.4 L Pressure – Pressure – kpa = 1 atm = 760 mmHg = 760 torr

Boyle’s Law Pressure – Volume Relationship Pressure – Volume Relationship P 1 V 1 = P 2 V 2 Example: Example: A high – altitude balloon contains 30.0 L of helium gas at 103 kPa. What is the volume when the balloon rises to an altitude where the pressure is only 25.0 kPa? (Assume STP)

P 1 = 103 kPaV 2 = ? L V 1 = 30.0 L P 2 = 25.0 kPa (103 kPa)(30.0 L) = (25.0 kPa)(V 2 ) V 2 = 124 L

Charles’s Law Temperature – Volume Relationship V 1 = V 2 T 1 = T 2 **Temperature in Kelvin. Example: A balloon inflated in a room at 24 o C has a volume of 4.00 L. The balloon is then heated to a temperature of 58 o C. What is the new volume if the pressure remains constant?

V 1 = 4.00 LV 2 = ? L T 1 = 24 o C = 297 K T 2 = 58 o C = 331 K (4.00L) = V 2 (297 K) (331 K) V 2 = 4.46 L

Combined Gas Law Combines the 3 gas laws P 1 V 1 = P 2 V 2 T 1 = T 2 T 1 = T 2 Example: The volume of a gas – filled balloon is 30.0 L at 40 o C and 153 kPa pressure. What volume will the balloon have at standard temperature and pressure (STP)?

V 1 = 30.0 LV 2 = ? L T 1 = 40 o C = 313 K T 2 = 273 K P 1 = 153 kPa P 2 = kPa (153 kPa)(30.0 L) = (101.3 kPa)(V 2 ) ( 313 K ) (273 K ) V 2 = 39.5 L

Ideal Gas Law (Universal Gas Law) Adding # of moles Adding # of moles PV = nRT P = pressure V = volume n = # of moles R = ideal gas constant (8.31 L x kPa / K mole) T = temperature

Example: You fill a rigid steel cylinder that has a volume of 20.0 L with nitrogen gas (N 2 ) to a final pressure of 2.00 x 10 4 kPa at 28 o C. How many moles of N 2 does the cylinder contain?

P = 2.00 x 10 4 kPa n = ? moles of N 2 V = 20.0 L T = 28 o C (2.00 x 10 4 kPa)(20.0 L) = n(8.31)(301 K) N = 160 moles N 2