Chapter 13 States of Matter
The Four Major States of Matter Solid Liquid Gas Plasma
The Nature of Gases 13.1
Characteristics of a Gas Indefinite shape, takes the shape of its container Indefinite volume, takes the volume of its container AT THIS POINT IN CHEMISTRY, we assume that the particles have no attractions to each other! Particles move to fill all available space
Gas in use at a Hospital
Kinetic Theory and a Model for Gases Kinetic energy is energy of motion Kinetic theory states that all matter consists of tiny particles that are in constant motion
What are the 3 assumptions of the kinetic theory? KEY QUESTION What are the 3 assumptions of the kinetic theory? The particles in a gas are considered to be small, hard spheres with an insignificant volume The motion of the particles in a gas is rapid, constant, and random All collisions between particles are perfectly elastic
Gas Pressure Gas pressure results from the force exerted by a gas per unit surface area of an object Gas pressure is caused by the collisions of gas particles with a container MISCONCEPTION: Gas particles are caused by colliding with each other!
Figure 13.1 Gas Pressure You can see the pressure being caused by the particles hitting the container!
How does kinetic theory explain gas pressure? KEY QUESTION How does kinetic theory explain gas pressure? Gas pressure is the result of a lot of rapidly moving particles of a gas colliding with an object.
What is the difference between gas pressure and atmospheric pressure? An empty space with no particles and no pressure is called a vacuum Atmospheric pressure is caused by the collisions of atoms and molecules in air with objects What is the difference between gas pressure and atmospheric pressure? Gas pressure occurs in a container and atmospheric pressure occurs in the atmosphere! Standard atmosphere is the pressure required to support 760 mm of mercury in a mercury barometer at 25oC
STP is defined as 0oC and a pressure of 1 atm! REMEMBER STP is defined as 0oC and a pressure of 1 atm!
Kinetic Energy and Temperature When a substance is heated, its particles absorb energy (some is then stored in the particles) This stored portion of the energy, or potential energy, does not raise the temperature of the substance However, this energy does speed up the particles (meaning increase their kinetic energy)
KEY QUESTION What is the relationship between the temperature in kelvins and the average kinetic energy of particles? The temperature in kelvins is directly proportional to the average kinetic energy of the particles of the substance
The Nature of Liquids 13.2
Characteristics of Liquids Indefinite shape, takes the shape of its container Has a fixed volume, does not change The particles are attracted to each other, but not as strong as those that are in a solid The particles are free-flowing, almost incompressible Tend to expand when heated
Common Liquids
A Model for Liquids According to the kinetic theory there are no attractions between the particles in a gas, but there are attractions between the particles in a liquid These attractions keep the particles in a liquid close together, this is the reason why liquids have definite volumes
What factors determine the physical properties of a liquid? KEY QUESTION What factors determine the physical properties of a liquid? The motion of the particles in a liquid and the attractions between the particles (intermolecular).
The particles in a liquid are closer together than those in a gas because of the intermolecular forces, making the liquids more dense than a gas; therefore, increasing the pressure on a liquid has little effect on its volume because these particles are already close together, this is also true for a solid; this explains why liquids and solids are known as condensed states of matter
Evaporation When a liquid converts to a gas or vapor the process is called vaporization When as liquid converts to a gas or vapor at the surface of a liquid WITOUT boiling the process is referred to as evaporation; meaning it occurs naturally without heat
What is the relationship between evaporation and kinetic energy? KEY QUESTION What is the relationship between evaporation and kinetic energy? During evaporation only those molecules with a certain minimum kinetic energy can escape from the surface of the liquid.
Liquids evaporates faster when heated, this is due to the increase in average kinetic energy of the particles The added energy allows the particles to overcome the attractive forces that causes them to be in a liquid state The particles with the highest kinetic energy evaporates first (meaning they are moving faster) The particles that remain as a liquid are moving slower and has lower average kinetic energy than those that have evaporated
Vapor Pressure The evaporation of a liquid in a closed system differs from evaporation in an open system The measure of the force exerted by a gas above a liquid is called vapor pressure Vapor pressure occurs in a closed system
KEY QUESTION When can a dynamic equilibrium exist between a liquid and its vapor? This occurs in a closed system. The system has to have a constant vapor pressure. Meaning, dynamic equilibrium exists between the vapor and the liquid.
REMEMBER A gas is a gas at room temperature and a vapor is a liquid at room temperature!
Vapor pressure and temperature has a direct relationship An increase in the temperature of a liquid increases the vapor pressure, this is because when particles are heated they the kinetic energy is increased
Under what conditions does boiling occur? Boiling Point KEY QUESTION Under what conditions does boiling occur? When a liquid is heated to a temperature at which particles throughout the liquid have enough kinetic energy to vaporize, the liquid begins to boil.
The boiling point is the temperature at which the vapor pressure of the liquid is just equal to the external pressure on the liquid Liquids do not always boil at the same temperature, this is because a liquid boils when the vapor pressure is equal to the external pressure When a liquid boils depends on where you are, high altitude (boiling points decrease) or low altitude (boiling points increase)! Normal boiling point is defined as the boiling point of a liquid at a pressure of 101.3 kPa or 1 atm
The Nature of Solids 13.3
Characteristics of Solids Definite (fixed) shape Definite (fixed) volume Particles stay in one spot and vibrate Very strong intermolecular forces between the particles
A Model for Solids Key Question How are the structure and properties if solids related? The properties of solids reflect the orderly arrangement of their particles and the fixed locations of their particles (caused by intermolecular forces).
When a solid is heated, it melts because the intermolecular forces are being broken between the particles Melting point is the temperature at which a solid changes into a liquid Freezing point is the temperature at which a liquid changes into a solid When the temperature is decrease the particles in a liquid began to move slowly causing them to have less distance between them, this decrease in distance allows for the intermolecular attractions bring the particles close together
Changes of State 13.4
When can sublimation occur? The change of a substance from a solid to a vapor without becoming a liquid first is called sublimation Vapor pressure allows for sublimation to occur KEY QUESTION When can sublimation occur? When a solid has a vapor pressure that exceeds atmospheric pressure at to near room temperature.
A line separates the two regions that are in equilibrium. Phase Diagrams A phase diagram gives the conditions of temperature and pressure at which a substance exists as solid, liquid, or gas (vapor) The triple point is when a solid, liquid, and a gas can coexist at the same time KEY QUESTION How are the conditions at which phases are in equilibrium represented on a phase diagram? A line separates the two regions that are in equilibrium.
Phase Diagram See Number 7 Let’s Highlight
The temperature remains the same! What do you notice about the temperature when H2O is changing phases? (SL or LG) The temperature remains the same! S L 0oC and L G 100oC
SUMMARY OF STATE CHANGES
Plasma 13.5 (Not in Textbook)
Plasma
Characteristics of Plasma Indefinite shape, takes the shape of the container Indefinite volume Particle have no attraction to each other, this is due to the free flowing positive ions which repel each other
Plasma is a gaseous mixture of freely moving positive ions and electrons This state of matter is found in the sun, stars, lightning bolts, and the ionosphere (upper region of the Earth’s atmosphere) Plasma can be created by heating a gas or subjecting it to a strong electromagnetic field applied with a laser or generator Plasma technology is being used in electric discharge lamps, electric arcs (welding), and waste converters