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CHAPTER 6 : PROPERTIES OF MATTER - Coggle Diagram
CHAPTER 6 : PROPERTIES OF MATTER
States of matter
The 4 states of matter are:
Solid
Liquid
Gas
Plasma
The Solid State
Solids have a fixed volume and shape
The particles of solids vibrate but stay in a relatively fixed position
Crystals form if the particles are arranged in a regular sequence
The liquid state
Liquids have a fixed volume but take the shape of the container
The atoms move relative to one another but still stay close together
Liquids can only exist for a limited temperature range
The gas state
Gases have no fixed volume or shape; they expand to fill all available space and can be compressed
Atoms in a gas are free to move independently from each other (moving at random)
Plasma
Plasma is gas that has ionised due to very high temperature (eg the sun's corona)
The particles are electrically charged and is affected by magnetic and electric fields
Changes of states
Matter can change between states when the temperature or pressure of a system is changed
The processes that describe the changes of state are shown in the following figure
Phase change
transitions between different states of matter
Heating causes the particles of matter to absorb energy, move more vigorously and separate further apart
Cooling causes the particles to move less vigorously and come closer together
Phase diagram of a single component system
A phase diagram shows the various phases (or states) of a system as a function of pressure and temperature
A phase diagram for a single component system is for a pure compound, for example pure H2O and CO2
A phase diagram summarizes the conditions at which a substance exists as a solid, liquid, or gas and the places where equilibria exist between phases.
Phase Diagram of Water
The sublimation point curve is a line where the solid and the gas phase are in equilibrium
The boiling point curve is a line where the liquid and gas phase are in equilibrium The normal boiling point of H2O is 100oC at 1 atm
The melting point curve is a line where the solid and the liquid phase are in equilibrium
The normal melting point of water is 0oC at 1 atm
The melting point line for water slopes to the left ) because as pressure is increased the melting point of H2O is decreased
The triple point occur at 0.006 atm and 0.01oC
The critical point occur at 216 atm and 374oC
PROPERTIES OF GASES AND GAS LAWS
Three variables are used to measure gases: pressure, volume, and temperature
Volume of a gas is equal to the volume of the container that holds the gas
Temperature is the heat energy due to the motion of the gas particles
Pressure is force per area
Boyle’s Law
The volume of a given mass of a gas is inversely proportional to pressure at constant temperature
Comparing two conditions, initial (1) and final (2), the equation for Boyles Law is
Charles Law
The volume of a given mass of a gas is proportional to absolute temperature at constant pressure
-Comparing two conditions, initial (1) and final (2), the equation for Charles Law is
Avogadro’s Law
The volumes of gases are proportional to the number of atoms or molecules
1 mole gas = 22.4 L at STP
The Ideal Gas Law
The Ideal Gas Law is derived by combining Boyle’s Law, Charle’s Law and Avogadro’s Law
A gas which obeys the Ideal Gas Law is called an ideal gas (perfect gas)
The Ideal Gas Law equation is
Combined Gas Law
We derive the Combined gas Law by equating two sets of Ideal Gas Laws at two conditions
Gay-Lussac's Law
The pressure of a given mass of a gas is proportional to absolute temperature at constant volume
P T
Comparing two conditions, the equation for the law is:
Dalton's Law of Partial Pressure
The Dalton' law is generally used for determining the actual pressure of a gas collected by the water displacement method:
PH2O vapor + Pdry gas = Ptot (measured)
Graham's Law of Effusion (Diffusion)
Diffusion : Rate at which two gases mix
Effusion : Rate at which a gas moves through a small hole
The rate of effusion of a gas is inversely proportional to the square root of its density
Comparing effusion of two gases, A and B
Since density (p) is proportional to molecular mass (M), therefore, density can be replaced by M
Real Gases and van der Waals Equation
Gases behave like ideal (perfect) gases at low pressure and high temperature
An equation used to represent a gas that is non ideal is the van der Waals equation :
This equation accommodates corrections for pressure and volume :
Particles of a real gas have volume The actual volume the particles have to move around in is Vreal = Videal – nb
Particles of a real gas attract each other The actual pressure exerted by the gas is Preal = Pideal + (an2)/ V2
Kinetic Theory of Gases
The Kinetic Theory of Gases is based on the following assumptions and describes the properties of an ideal gas:
The volumes of gas particles are negligible (very small)
Intermolecular forces do not exist between gas particles
Gas particles move in random motions and collide without energy loss
The kinetic energy of a gas is directly proportional to absolute temperature
Properties of Liquid
Viscosity
Viscosity depends on any factor that can influence the ease with which molecules slip past each other
Liquids tend to become more viscous as the size of molecules become larger, as the amount of intermolecular bonding increases and the temperature decreases
Surface tension
The force that controls the shape of the liquid is called the surface tension
Below the surface of the liquid, the force between molecules is the same in all directions, but at the surface the force of attraction pulls the molecules into the liquid
As a result, the liquid takes on the shape of a sphere
Vapor Pressure
The vapor pressure of a liquid is the pressure of the vapor (gas) above the liquid at a given temperature
A liquid open to the air will (over time) evaporate completely; however in a closed container some of the evaporated molecules may return to the liquid
Over time an equilibrium will be established (the rate at which molecules evaporate is equal to the rate at which molecules return to the liquid) The gas pressure under this equilibrium condition is called the vapor pressure
Types of solid
two types :
Crystalline solids
Amorphous solids
Crystalline solids
The atoms, molecules or ions are arranged in a regular pattern
They exhibit anisotropic properties
They have sharp (specific) melting points
Amorphous solids
Particles have no regular pattern of arrangement
Melt over a range of temperatures
Unit Cells, Crystal Lattices and Crystal System
A unit cell is the smallest basic unit of a crystal that can be repeated in three dimensions throughout the crystal lattice
A crystal lattice is the repeating pattern of particles in a crystalline solid
A crystal system is a method of classifying crystalline substances on the basis of their unit cells
Number of units in a unit cell
The number of units (atoms, ions or molecules) in a unit cell can be calculated by applying the following rules:
A corner unit is shared by 8 unit cells = 1/8 unit per cell
A face unit is shared by 2 unit cells = ½ units per cell
An edge unit (at the edge of the unit cell) is shared by 4 unit cells = ¼ unit per cell
