Chapter 13 - Useful Advicekdteel.weebly.com/uploads/4/9/7/0/4970193/chem12_c13_l1_lo.pdf · Chapter...
30
13.1 The Nature of Gases > 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Chapter 13 States of Matter 13.1 The Nature of Gases 13.2 The Nature of Liquids 13.3 The Nature of Solids 13.4 Changes of State
Transcript of Chapter 13 - Useful Advicekdteel.weebly.com/uploads/4/9/7/0/4970193/chem12_c13_l1_lo.pdf · Chapter...
13.1 The Nature of Gases >
1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Chapter 13 States of Matter 13.1 The Nature of Gases 13.2 The Nature of Liquids 13.3 The Nature of Solids 13.4 Changes of State
13.1 The Nature of Gases >
2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
What factors most strongly affect the weather?
CHEMISTRY & YOU
The atmosphere is a gas, and the factors that determine the behavior of gases—temperature and pressure—affect the weather in the atmosphere.
13.1 The Nature of Gases >
3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Theory and a Model for Gases
Kinetic Theory and a Model for Gases What are the three assumptions of the kinetic theory as it applies to gases?
13.1 The Nature of Gases >
4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
The word kinetic refers to motion.
Kinetic Theory and a Model for Gases
• The energy an object has because of its motion is called kinetic energy.
13.1 The Nature of Gases >
5
Kinetic Energy
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
13.1 The Nature of Gases >
6 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
The word kinetic refers to motion.
Kinetic Theory and a Model for Gases
• The energy an object has because of its motion is called kinetic energy.
• According to the kinetic theory, all matter consists of tiny particles that are in constant motion.
• The particles in a gas are usually molecules or atoms.
13.1 The Nature of Gases >
7 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Theory and a Model for Gases
The kinetic theory as it applies to gases includes the following fundamental assumptions about gases.
The particles in a gas are considered to be small, hard spheres with an insignificant volume.
– Within a gas, the particles are relatively far apart compared with the distance between particles in a liquid or solid.
– Between the particles, there is empty space.
– No attractive or repulsive forces exist between the particles.
13.1 The Nature of Gases >
8 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Bromine molecule
Kinetic Theory and a Model for Gases
The kinetic theory as it applies to gases includes the following fundamental assumptions about gases.
The motion of particles in a gas is rapid, constant, and random.
– Gases fill their containers regardless of the shape and volume of the containers.
– An uncontained gas can spread out into space without limit.
– http://www.youtube.com/watch?v=Lf1kTsT0ebc&feature=results_video&playnext=1&list=PL4C6135C5D77E975D
13.1 The Nature of Gases >
9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Theory and a Model for Gases
The kinetic theory as it applies to gases includes the following fundamental assumptions about gases.
The motion of particles in a gas is rapid, constant, and random.
– The rapid, constant motion of particles in a gas causes them to collide with one another and with the walls of their container.
13.1 The Nature of Gases >
10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Theory and a Model for Gases
The kinetic theory as it applies to gases includes the following fundamental assumptions about gases.
The motion of particles in a gas is rapid, constant, and random.
– The particles travel in straight- line paths until they collide with
another particle.
– The particles change direction only when they rebound from collisions.
13.1 The Nature of Gases >
11 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Theory and a Model for Gases
The kinetic theory as it applies to gases includes the following fundamental assumptions about gases.
All collisions between particles in a gas are perfectly elastic.
– During an elastic collision, kinetic energy is transferred without loss from one particle to another.
– The total kinetic energy remains constant.
13.1 The Nature of Gases >
12 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Gas Pressure
Gas pressure results from the force exerted by a gas per unit surface area of an object. • Moving bodies exert a force when they collide
with other bodies.
13.1 The Nature of Gases >
13 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Gas Pressure
Gas pressure is the result of billions of rapidly moving particles in a gas simultaneously colliding with an object.
13.1 The Nature of Gases >
14 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Gas Pressure
• If no particles are present, no collisions can occur. Consequently, there is no pressure.
• An empty space with no particles and no pressure is called a vacuum.
Gas pressure is the result of billions of rapidly moving particles in a gas simultaneously colliding with an object.
13.1 The Nature of Gases >
15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Gas Pressure
Air exerts pressure on Earth because gravity holds the particles in air within Earth’s atmosphere. • The collisions of atoms and molecules in
air with objects results in atmospheric pressure.
• Atmospheric pressure decreases as you climb a mountain because the density of Earth’s atmosphere decreases as the elevation increases.
13.1 The Nature of Gases >
16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Gas Pressure
A barometer is a device that is used to measure atmospheric pressure.
Vacuum
Atmospheric pressure
760 mm Hg (barometric pressure)
253 mm Hg
Sea level On top of Mount Everest
13.1 The Nature of Gases >
17 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
When weather forecasters state that a low-pressure system is moving into your region, it usually means that a storm is coming. What do you think happens to the column of mercury in a barometer as a storm approaches? Why?
CHEMISTRY & YOU
When a storm approaches, the column of mercury goes down, indicating a decrease in atmospheric pressure.
13.1 The Nature of Gases >
18 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Gas Pressure
The SI unit of pressure is the pascal (Pa).
• Two older units of pressure are commonly used.
– millimeters of mercury (mm Hg)
– atmospheres (atm)
13.1 The Nature of Gases >
19 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Energy and Temperature
Kinetic Energy and Temperature What is the relationship between the temperature in kelvins and the average kinetic energy of particles?
13.1 The Nature of Gases >
20 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Energy and Temperature
Average Kinetic Energy At any given temperature, the particles of all substances, regardless of physical state, have the same average kinetic energy.
13.1 The Nature of Gases >
21 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
The figure below shows the distribution of kinetic energies of water molecules at two different temperatures.
Interpret Graphs
• The green curve shows the distribution of kinetic energy in cold water.
• The purple curve shows the distribution of kinetic energy in hot water.
13.1 The Nature of Gases >
22 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Energy and Temperature
Average Kinetic Energy The average kinetic energy of the particles in a substance is directly related to the substance’s temperature. • An increase in the average kinetic energy of
the particles causes the temperature of a substance to rise.
• As a substance cools, the particles tend to move more slowly, and their average kinetic energy decreases.
13.1 The Nature of Gases >
23 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Energy and Temperature
Average Kinetic Energy Absolute zero (0 K, or –273.15oC) is the temperature at which the motion of particles theoretically ceases. • No temperature can be lower than absolute
zero.
• Absolute zero has never been produced in the laboratory. – A near-zero temperature of about 0.000 000 000 1 K,
which is 0.1 nanokelvin, has been achieved.
13.1 The Nature of Gases >
24 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Kinetic Energy and Temperature
Average Kinetic Energy and Kelvin Temperature
The Kelvin temperature of a substance is directly proportional to the average kinetic energy of the particles of the substance.
13.1 The Nature of Gases >
25 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
What is the result of increasing the temperature of a gas sample? A. A decrease in the average kinetic
energy of the sample
B. No effect on the sample
C. An increase in the average kinetic energy of the sample
D. The particles slow down.
13.1 The Nature of Gases >
26 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
What is the result of increasing the temperature of a gas sample? A. A decrease in the average kinetic
energy of the sample
B. No effect on the sample
C. An increase in the average kinetic energy of the sample
D. The particles slow down.
13.1 The Nature of Gases >
27
Temperature vs. Heat
Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
13.1 The Nature of Gases >
28 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Glossary Terms
• kinetic energy: the energy an object has because of its motion
• kinetic theory: a theory explaining the states of matter, based on the concept that all matter consists of tiny particles that are in constant motion
• gas pressure: results from the force exerted by a gas per unit surface area of an object; due to collisions of gas particles with the object
13.1 The Nature of Gases >
29 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Glossary Terms
• vacuum: a space where no particles of matter exist
• atmospheric pressure: the pressure exerted by atoms and molecules in the atmosphere surrounding Earth, resulting from collisions of these particles with objects
• barometer: an instrument used to measure atmospheric pressure
13.1 The Nature of Gases >
30 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.
Glossary Terms
• Pascal (Pa): the SI unit of pressure
• standard atmosphere (atm): a unit of pressure; it is the pressure required to support 760 mm of mercury in a mercury barometer at 25°C
