Please enable JavaScript.
Coggle requires JavaScript to display documents.
Chapter 6 (State of Matter) - Coggle Diagram
Chapter 6 (State of Matter)
Types of matter
Solid
Properties
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
Liquid
Properties
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
Gas
Properties
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
Properties
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 state
Phase diagram
What is it
A phase diagram shows the various phases (or states) of a system as a function of pressure and temperature
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.
Properties of gases and gas laws
Laws
Boyle's Law
Gay-lussac's Law @ Pressure Law
Charles' Law
Avogadro's Law
Ideal Gas Law
PV = nRT,
Where P = pressure in atm, V = volume, T = temperature in Kelvin, n = number of moles
The Ideal Gas Law can be used to determine density
(p = mass per volume) or molar mass (g mole-1) of a gas
Combined Law
Derive the Combined gas Law by equating two sets of Ideal Gas Laws at two conditions (assuming nR is constant and 1 initial, 2 final)
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:
The partial pressures of gases eg A and B in a mixture can be also calculated as follows:
Ptot = Pa +Pb + Pc.....
Graham's Law of Effusion (Diffusion)
The rate of effusion of a gas is inversely proportional to the square root of its density or molar mass
Rate of gas = mass (g) / time (s)
Real Gases and van der Waals Equation
Gases behave like ideal (perfect) gases at low pressure and high temperature (High pressure and low temperature causes gases to behave non-ideally)
Raoult's Law
Properties of Solid
Types of Solid
Crystalline solid
Types of crystalline solid
Ionic crystals
Properties
Consist of positive and negative ions alternately arranged
Have high melting points, tend to be hard or brittle (reflecting strong electrostatic forces)
Conduct electricity in the molten or soluble state (eg NaCl, CaCl2)
Molecular crystals
Properties
A network of covalently bonded atoms forming a gigantic molecule
Have high melting points and tend to be hard (strong covalent bonds)
Non conductors (eg Diamond (C), quartz, SiO2)
Covalent crystals
Properties
A network of covalently bonded atoms forming a gigantic molecule
Have high melting points and tend to be hard (strong covalent bonds)
Non conductors (eg Diamond (C), quartz, SiO2)
Metallic crystals
Properties
Consist of positive metal ions
Melting points and hardness depend on the nuclear charge and electrons
Conductors (eg Cu, Hg, Na)
Amorphous solid
Particles have no regular pattern of arrangement (consist of intertwined chainlike particles/molecules)
Melt over a range of temperatures (eg Rubber, glass, sulfur)
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
Crystal system
Types
Cubic
Tetragonal
Orthorhombic
Monoclinic
Triclinic
Hexagonal
Rhombohedral
Cubic system
Types of lattice arrangement
Simple cubic lattice (has a lattice point at every corner of the unit cell)
Rules of calculating the no. of units in a cell
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
A body unit (in the center of the unit cell) is unique to 1 unit cell = 1 unit per cell
Body-centered cubic lattice ( has a lattice point at every corner and additional lattice point in the center of the unit cell
Face centered cubic lattice ( has a lattice point at every corner and an additional atom at each of its faces)
Atomic radius and Density
The radius of an atom can be calculated from the crystal structure of a substance using data obtained from a method known as X-ray analysis
Kinetic Theory of Gases
The Kinetic Theory of Gases is based on the following assumptions and describes the properties of an ideal gas:
Intermolecular forces do not exist between gas particles.This explains why gas particles do not influence each other and fills up a container
Gas particles move in random motions and collide without energy loss (elastic collisions).This explains why the gas particles collide with one another and the walls of a container without energy lose
The kinetic energy of a gas is directly proportional to absolute temperature.This explains why when gas is heated the particles move faster
The volumes of gas particles are negligible (very small). This explains why gases are compressible
Equations involving Kinetic Energy (KE) and velocity (u) of gas molecules are given as follows: KE = 1/2mu2 = 3/2kT, Substitute k and m, k = R/NA and m = M/NA, Where, R = gas constant, M = molecular mass, NA = Avogadro's number,
Properties of Liquid (Further Explanation)
Viscosity
Viscosity is a measure of the resistance to flow (measured in units called poise, pronounced 'pwahz')
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 (a shape that has the smallest surface area)
Vapour 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
Colligative Properties
Vapor pressure lowering
The vapor pressure of a solution containing nonvolatile solute is lower than the pure solvent
Why is vapor pressure lowered ? There are more solvent molecules on the surface of the pure solvent (left figure) than there are on the surface of the solution (right figure)
The solvent molecules in the solution will have a lower probability to escape the solution than the pure solvent, resulting in lower rate of vapor formation, thus lower vapor pressure
Boiling point elevation
The boiling point of a solution containing nonvolatile solute is greater than the boiling point of the pure solvent
Why is boiling point elevated? The vapor pressure of a solution is lower (1st colligative property), therefore a higher temperature is required to boil a solution
Freezing point depression
The freezing point of a solution containing nonvolatile solute is lower than the boiling point of the pure solvent
Why is freezing point lowered ? In order for a liquid to freeze it must achieve a very ordered state. Solutes in the liquid is inherently less ordered and therefore, a solution is more difficult to freeze than the pure solvent
Osmotic pressure
Osmosis is the selective passage of solvent molecules through a porous membrane from a dilute solution to a more concentrated one.
A semipermeable membrane allows the passage of solvent molecules but blocks the passage of solute molecules.
