Gr 11 Physical Sciences: June Hard

7 Electrostatics

7.1 Coulomb's Law

• Like charges repel each other, while unlike charges attract each other.
• The electrostatic force between charges increases when the magnitude of the charges increases or the distance between the charges decreases.
• Coulomb's law states that the magnitude of the electrostatic force between two point-like charges is inversely proportional to the square of the distance between the charges.
• The magnitude of the electrostatic force is proportional to the product of the charges.
• Coulomb's law is similar in form to Newton's universal law of gravitation, both are inverse-square laws.

7.2 Electric Field

Definition of Electric Field

• An electric field is a region of space in which an electric charge will experience a force.
• The direction of the electric field at a point is the direction of the force that a positive test charge would experience if placed at that point.

Representing Electric Fields

• Electric field lines show the direction and strength of the electric field.
• The strength of the electric field is proportional to the number of field lines per unit area.
• Field lines are closer together where the field is stronger.

Electric Fields Around Different Charge Configurations

• For a positive charge, the electric field lines point away from the charge.
• For a negative charge, the electric field lines point towards the charge.
• For two unlike charges, the electric field lines start from the positive charge and end at the negative charge.
• For two like charges, the electric field lines repel from both charges.

Electric Field Strength

• The electric field strength is defined as the force per unit charge that a test charge would experience at a point.
• The electric field strength is proportional to the force and inversely proportional to the charge.
• The units of electric field strength are newtons per coulomb (N·C^{-1}).

8 Electromagnetism

8.1 Magnetic Field Associated with a Current

• A current-carrying wire generates a magnetic field around the wire.
• The magnetic field lines are oriented perpendicular to the direction of the current flow.
• The direction of the magnetic field can be determined using the Right Hand Rule.
• The strength of the magnetic field is proportional to the current.

Visualizing Magnetic Fields

• The magnetic field around a wire can be visualized as concentric circles with the wire at the center.
• The magnetic field lines form a pattern that converges through the loop, creating a magnetic dipole with a distinct north and south pole.

Real-World Applications

• Electromagnets are devices that generate a magnetic field when an electric current flows through a coil of wire.
• Electromagnets are used in various applications such as electric motors, generators, relays, and magnetic storage devices.
• Overhead power lines carrying electric current generate magnetic fields, which can impact the environment.

8.2 Faraday's Law of Electromagnetic Induction

Current Induced by a Changing Magnetic Field

• Faraday's Law of Electromagnetic Induction states that a changing magnetic field induces an electric field.
• The induced emf is proportional to the rate of change of the magnetic flux.

Magnetic Flux

• Magnetic flux is the amount of magnetic field that passes through a surface.
• The magnetic flux is proportional to the magnetic field strength and the area of the surface.

Faraday's Law of Electromagnetic Induction

• The induced emf is proportional to the rate of change of the magnetic flux.
• The direction of the induced emf is determined by the direction of the changing magnetic field.

Direction of Induced Current

• The induced current in a conductor always opposes the change in magnetic flux.
• The direction of the induced current is determined by the Right Hand Rule.

Induction

• Electromagnetic induction is utilized in various applications, most notably in electrical generators.
• Self-induction occurs when a changing magnetic field produced by a changing current in a wire induces a voltage along the same wire.

Lenz's Law

• Lenz's Law states that the induced current will create a magnetic field that opposes the change in the magnetic flux.

9 Electric Circuits

9.1 Ohm's Law

• Ohm's Law states that the amount of electric current through a metal conductor at a constant temperature is proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.
• The resistance of the conductor is constant, independent of the voltage applied across it or current passed through it.
• Ohm's Law is a linear relationship between voltage and current.### Electrical Conductors and Resistors
• Ohmic conductors: have a linear relationship between current and voltage, and their resistance remains constant
  • Examples: circuit resistors, nichrome wire
• Non-ohmic conductors: do not have a linear relationship between current and voltage, and their resistance changes with temperature
  • Examples: light bulbs, diodes, transistors

Series and Parallel Circuits

• Series circuits: have only one path for current to flow, and the total resistance is the sum of individual resistances
  • Total resistance (Rs) = R1 + R2 + ... + Rn
  • Current is the same through all components
  • Voltage across each resistor is proportional to its resistance
• Parallel circuits: have multiple paths for current to flow, and the total resistance is less than the smallest individual resistance
  • Total resistance (Rp) = 1/(1/R1 + 1/R2 + ... + 1/Rn)
  • Voltage is the same across all components
  • Total current is the sum of currents through each parallel path

Power and Energy

• Power (P) is the rate at which work is done, measured in joules per second (J/s or watts, W)
  • P = I × V (power is directly proportional to both current and voltage)
  • P = I² × R (power is directly proportional to the square of current multiplied by resistance)
  • P = V² / R (power is directly proportional to the square of voltage divided by resistance)
• Energy (E) is the total amount of work done, measured in joules (J)
  • E = P × t (energy is the product of power and time)
  • 1 kilowatt-hour (kWh) = 1 kilowatt (kW) × 1 hour

Chemical Bonds

• Atoms form bonds to achieve a more stable electron configuration, similar to the noble gases
• Valence electrons are the outermost energy level electrons involved in bonding
• Lewis diagrams and spectroscopic notation are used to represent electron configurations

Covalent Bonds

• Formed when pairs of electrons are shared between atoms
• Types of covalent bonds:
  • Single bonds: one pair of electrons shared
  • Double bonds: two pairs of electrons shared
  • Triple bonds: three pairs of electrons shared
• Coordinate (dative) covalent bonds: both electrons in the bond come from the same atom

Molecular Shape

• Molecular shape determines how molecules interact and react with other molecules
• Valence shell electron pair repulsion (VSEPR) theory predicts molecular shape
• Steps to predict molecular shape:
  1. Draw the Lewis diagram
  2. Count electron pairs
  3. Determine basic geometry
  4. Write the final answer
• Examples of molecular shapes:
  • BeCl₂: linear
  • BF₃: trigonal planar
  • NH₃: trigonal pyramidal

Electronegativity

• Electronegativity is the ability of an atom to attract electrons towards itself
• Importance of electronegativity:
  • Influences the nature of bonds between atoms
  • Affects the polarity of molecules
  • Determines the solubility, melting points, and boiling points of molecules
• Calculating electronegativity differences:
  1. Identify the electronegativity values of the two atoms
  2. Subtract the smaller value from the larger value
• Electronegativity and bonding:
  • Non-polar covalent bond: electronegativity difference is 0
  • Weak polar covalent bond: electronegativity difference between 0.1 and 1
  • Strong polar covalent bond: electronegativity difference between 1.1 and 2
  • Ionic bond: electronegativity difference greater than 2.1

Energy and Bonding

• Bond length is the distance between the nuclei of two adjacent atoms when they form a bond
• Bond energy is the amount of energy required to break a bond between two atoms
• Factors influencing bond strength:
  • Bond length
  • Atom size
  • Number of bonds
• Energy changes in bond formation:
  • Decreasing energy: attractive forces dominate
  • Minimum energy point: bond formation
  • Increasing energy: repulsive forces dominate
• Graphical representation of energy changes:
  • Energy minimum (X): bond formation
  • Energy increase beyond X: repulsive forces dominate### Hydrogen Bonds
• Hydrogen bonds occur in molecules where hydrogen is covalently bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine.
• Hydrogen bonds are a relatively strong intermolecular force that forms between the hydrogen atom of one molecule and the electronegative atom of another molecule.
• Example: Water molecules form hydrogen bonds between the hydrogen atom of one molecule and the oxygen atom of another.

Intermolecular and Interatomic Forces

• Intermolecular forces occur between molecules and include dipole-dipole forces, hydrogen bonds, and London dispersion forces.
• Interatomic forces occur within molecules and include covalent, ionic, and metallic bonds.
• Interatomic forces are stronger than intermolecular forces.

Properties Affected by Intermolecular Forces

• Phase of Matter: Strong intermolecular forces result in solids, while weak intermolecular forces result in gases.
• Melting and Boiling Points: Substances with strong intermolecular forces have high melting and boiling points, while substances with weak intermolecular forces have low melting and boiling points.
• Viscosity: Substances with strong intermolecular forces are more viscous.
• Density: Solids are often the densest phase due to strong intermolecular forces.
• Thermal Expansion: As substances are heated, their molecules move more vigorously and expand.
• Thermal Conductivity: Metals have high thermal conductivity due to free electrons.

Investigation of Intermolecular Forces

• Evaporation: Substances with weaker intermolecular forces evaporate faster.
• Surface Tension: Stronger intermolecular forces result in higher surface tension.
• Solubility: Substances dissolve in solvents with similar intermolecular forces.
• Boiling Point: Substances with strong intermolecular forces have higher boiling points.
• Capillarity: Substances with strong intermolecular forces travel further up a narrow tube.

Molecular Size and Intermolecular Forces

• Larger molecules have stronger intermolecular forces.
• In organic compounds like alkanes, increasing the number of carbon atoms increases the boiling point and melting point due to stronger intermolecular forces.

The Chemistry of Water

• The unique microscopic structure of water is due to its polar nature, molecular shape, and intermolecular forces.
• Water molecules are held together by hydrogen bonds, which are responsible for many of its unique properties.

Unique Properties of Water

• Specific Heat: Water has a high specific heat, meaning it absorbs a lot of energy before its temperature changes significantly.
• Absorption of Infra-Red Radiation: Water can absorb infra-red radiation from the sun, acting as a heat reservoir and helping to moderate the Earth's climate.
• Melting Point and Boiling Point: Water has a melting point of 0°C and a boiling point of 100°C at standard pressure, allowing it to exist as a liquid over a wide range of temperatures.
• High Heat of Vaporisation: Water has a high heat of vaporisation, meaning a significant amount of energy is required to change water from liquid to gas.
• Less Dense Solid Phase: Water is less dense in its solid phase (ice) than in its liquid phase, which is crucial for maintaining liquid water on Earth and supporting aquatic life.

The Interactions of Water with Various Substances

• Water is an excellent solvent for many ionic and polar substances due to its polarity and hydrogen bonding.
• Water dissolves ionic compounds by surrounding the positive and negative ions with water molecules, stabilizing the ions in solution.
• Water dissolves many polar covalent compounds due to hydrogen bonding.
• Non-polar substances do not dissolve well in water due to the lack of attraction between water molecules and non-polar molecules.
• Water's solvent properties are essential for biological functions, nutrient transport, and environmental processes.

7 Electrostatics

7.1 Coulomb's Law

• Like charges repel each other, while unlike charges attract each other.
• The electrostatic force between charges increases when the magnitude of the charges increases or the distance between the charges decreases.
• Coulomb's law states that the magnitude of the electrostatic force between two point-like charges is inversely proportional to the square of the distance between the charges.
• The magnitude of the electrostatic force is proportional to the product of the charges.
• Coulomb's law is similar in form to Newton's universal law of gravitation, both are inverse-square laws.

7.2 Electric Field

Definition of Electric Field

• An electric field is a region of space in which an electric charge will experience a force.
• The direction of the electric field at a point is the direction of the force that a positive test charge would experience if placed at that point.

Representing Electric Fields

• Electric field lines show the direction and strength of the electric field.
• The strength of the electric field is proportional to the number of field lines per unit area.
• Field lines are closer together where the field is stronger.

Electric Fields Around Different Charge Configurations

• For a positive charge, the electric field lines point away from the charge.
• For a negative charge, the electric field lines point towards the charge.
• For two unlike charges, the electric field lines start from the positive charge and end at the negative charge.
• For two like charges, the electric field lines repel from both charges.

Electric Field Strength

• The electric field strength is defined as the force per unit charge that a test charge would experience at a point.
• The electric field strength is proportional to the force and inversely proportional to the charge.
• The units of electric field strength are newtons per coulomb (N·C^{-1}).

8 Electromagnetism

8.1 Magnetic Field Associated with a Current

• A current-carrying wire generates a magnetic field around the wire.
• The magnetic field lines are oriented perpendicular to the direction of the current flow.
• The direction of the magnetic field can be determined using the Right Hand Rule.
• The strength of the magnetic field is proportional to the current.

Visualizing Magnetic Fields

• The magnetic field around a wire can be visualized as concentric circles with the wire at the center.
• The magnetic field lines form a pattern that converges through the loop, creating a magnetic dipole with a distinct north and south pole.

Real-World Applications

• Electromagnets are devices that generate a magnetic field when an electric current flows through a coil of wire.
• Electromagnets are used in various applications such as electric motors, generators, relays, and magnetic storage devices.
• Overhead power lines carrying electric current generate magnetic fields, which can impact the environment.

8.2 Faraday's Law of Electromagnetic Induction

Current Induced by a Changing Magnetic Field

• Faraday's Law of Electromagnetic Induction states that a changing magnetic field induces an electric field.
• The induced emf is proportional to the rate of change of the magnetic flux.

Magnetic Flux

• Magnetic flux is the amount of magnetic field that passes through a surface.
• The magnetic flux is proportional to the magnetic field strength and the area of the surface.

Faraday's Law of Electromagnetic Induction

• The induced emf is proportional to the rate of change of the magnetic flux.
• The direction of the induced emf is determined by the direction of the changing magnetic field.

Direction of Induced Current

• The induced current in a conductor always opposes the change in magnetic flux.
• The direction of the induced current is determined by the Right Hand Rule.

Induction

• Electromagnetic induction is utilized in various applications, most notably in electrical generators.
• Self-induction occurs when a changing magnetic field produced by a changing current in a wire induces a voltage along the same wire.

Lenz's Law

• Lenz's Law states that the induced current will create a magnetic field that opposes the change in the magnetic flux.

9 Electric Circuits

9.1 Ohm's Law

• Ohm's Law states that the amount of electric current through a metal conductor at a constant temperature is proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.
• The resistance of the conductor is constant, independent of the voltage applied across it or current passed through it.
• Ohm's Law is a linear relationship between voltage and current.### Electrical Conductors and Resistors
• Ohmic conductors: have a linear relationship between current and voltage, and their resistance remains constant
  • Examples: circuit resistors, nichrome wire
• Non-ohmic conductors: do not have a linear relationship between current and voltage, and their resistance changes with temperature
  • Examples: light bulbs, diodes, transistors

Series and Parallel Circuits

• Series circuits: have only one path for current to flow, and the total resistance is the sum of individual resistances
  • Total resistance (Rs) = R1 + R2 + ... + Rn
  • Current is the same through all components
  • Voltage across each resistor is proportional to its resistance
• Parallel circuits: have multiple paths for current to flow, and the total resistance is less than the smallest individual resistance
  • Total resistance (Rp) = 1/(1/R1 + 1/R2 + ... + 1/Rn)
  • Voltage is the same across all components
  • Total current is the sum of currents through each parallel path

Power and Energy

• Power (P) is the rate at which work is done, measured in joules per second (J/s or watts, W)
  • P = I × V (power is directly proportional to both current and voltage)
  • P = I² × R (power is directly proportional to the square of current multiplied by resistance)
  • P = V² / R (power is directly proportional to the square of voltage divided by resistance)
• Energy (E) is the total amount of work done, measured in joules (J)
  • E = P × t (energy is the product of power and time)
  • 1 kilowatt-hour (kWh) = 1 kilowatt (kW) × 1 hour

Chemical Bonds

• Atoms form bonds to achieve a more stable electron configuration, similar to the noble gases
• Valence electrons are the outermost energy level electrons involved in bonding
• Lewis diagrams and spectroscopic notation are used to represent electron configurations

Covalent Bonds

• Formed when pairs of electrons are shared between atoms
• Types of covalent bonds:
  • Single bonds: one pair of electrons shared
  • Double bonds: two pairs of electrons shared
  • Triple bonds: three pairs of electrons shared
• Coordinate (dative) covalent bonds: both electrons in the bond come from the same atom

Molecular Shape

• Molecular shape determines how molecules interact and react with other molecules
• Valence shell electron pair repulsion (VSEPR) theory predicts molecular shape
• Steps to predict molecular shape:
  1. Draw the Lewis diagram
  2. Count electron pairs
  3. Determine basic geometry
  4. Write the final answer
• Examples of molecular shapes:
  • BeCl₂: linear
  • BF₃: trigonal planar
  • NH₃: trigonal pyramidal

Electronegativity

• Electronegativity is the ability of an atom to attract electrons towards itself
• Importance of electronegativity:
  • Influences the nature of bonds between atoms
  • Affects the polarity of molecules
  • Determines the solubility, melting points, and boiling points of molecules
• Calculating electronegativity differences:
  1. Identify the electronegativity values of the two atoms
  2. Subtract the smaller value from the larger value
• Electronegativity and bonding:
  • Non-polar covalent bond: electronegativity difference is 0
  • Weak polar covalent bond: electronegativity difference between 0.1 and 1
  • Strong polar covalent bond: electronegativity difference between 1.1 and 2
  • Ionic bond: electronegativity difference greater than 2.1

Energy and Bonding

• Bond length is the distance between the nuclei of two adjacent atoms when they form a bond
• Bond energy is the amount of energy required to break a bond between two atoms
• Factors influencing bond strength:
  • Bond length
  • Atom size
  • Number of bonds
• Energy changes in bond formation:
  • Decreasing energy: attractive forces dominate
  • Minimum energy point: bond formation
  • Increasing energy: repulsive forces dominate
• Graphical representation of energy changes:
  • Energy minimum (X): bond formation
  • Energy increase beyond X: repulsive forces dominate### Hydrogen Bonds
• Hydrogen bonds occur in molecules where hydrogen is covalently bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine.
• Hydrogen bonds are a relatively strong intermolecular force that forms between the hydrogen atom of one molecule and the electronegative atom of another molecule.
• Example: Water molecules form hydrogen bonds between the hydrogen atom of one molecule and the oxygen atom of another.

Intermolecular and Interatomic Forces

• Intermolecular forces occur between molecules and include dipole-dipole forces, hydrogen bonds, and London dispersion forces.
• Interatomic forces occur within molecules and include covalent, ionic, and metallic bonds.
• Interatomic forces are stronger than intermolecular forces.

Properties Affected by Intermolecular Forces

• Phase of Matter: Strong intermolecular forces result in solids, while weak intermolecular forces result in gases.
• Melting and Boiling Points: Substances with strong intermolecular forces have high melting and boiling points, while substances with weak intermolecular forces have low melting and boiling points.
• Viscosity: Substances with strong intermolecular forces are more viscous.
• Density: Solids are often the densest phase due to strong intermolecular forces.
• Thermal Expansion: As substances are heated, their molecules move more vigorously and expand.
• Thermal Conductivity: Metals have high thermal conductivity due to free electrons.

Investigation of Intermolecular Forces

• Evaporation: Substances with weaker intermolecular forces evaporate faster.
• Surface Tension: Stronger intermolecular forces result in higher surface tension.
• Solubility: Substances dissolve in solvents with similar intermolecular forces.
• Boiling Point: Substances with strong intermolecular forces have higher boiling points.
• Capillarity: Substances with strong intermolecular forces travel further up a narrow tube.

Molecular Size and Intermolecular Forces

• Larger molecules have stronger intermolecular forces.
• In organic compounds like alkanes, increasing the number of carbon atoms increases the boiling point and melting point due to stronger intermolecular forces.

The Chemistry of Water

• The unique microscopic structure of water is due to its polar nature, molecular shape, and intermolecular forces.
• Water molecules are held together by hydrogen bonds, which are responsible for many of its unique properties.

Unique Properties of Water

• Specific Heat: Water has a high specific heat, meaning it absorbs a lot of energy before its temperature changes significantly.
• Absorption of Infra-Red Radiation: Water can absorb infra-red radiation from the sun, acting as a heat reservoir and helping to moderate the Earth's climate.
• Melting Point and Boiling Point: Water has a melting point of 0°C and a boiling point of 100°C at standard pressure, allowing it to exist as a liquid over a wide range of temperatures.
• High Heat of Vaporisation: Water has a high heat of vaporisation, meaning a significant amount of energy is required to change water from liquid to gas.
• Less Dense Solid Phase: Water is less dense in its solid phase (ice) than in its liquid phase, which is crucial for maintaining liquid water on Earth and supporting aquatic life.

The Interactions of Water with Various Substances

• Water is an excellent solvent for many ionic and polar substances due to its polarity and hydrogen bonding.
• Water dissolves ionic compounds by surrounding the positive and negative ions with water molecules, stabilizing the ions in solution.
• Water dissolves many polar covalent compounds due to hydrogen bonding.
• Non-polar substances do not dissolve well in water due to the lack of attraction between water molecules and non-polar molecules.
• Water's solvent properties are essential for biological functions, nutrient transport, and environmental processes.

7 Electrostatics

7.1 Coulomb's Law

• Like charges repel each other, while unlike charges attract each other.
• The electrostatic force between charges increases when the magnitude of the charges increases or the distance between the charges decreases.
• Coulomb's law states that the magnitude of the electrostatic force between two point-like charges is inversely proportional to the square of the distance between the charges.
• The magnitude of the electrostatic force is proportional to the product of the charges.
• Coulomb's law is similar in form to Newton's universal law of gravitation, both are inverse-square laws.

7.2 Electric Field

Definition of Electric Field

• An electric field is a region of space in which an electric charge will experience a force.
• The direction of the electric field at a point is the direction of the force that a positive test charge would experience if placed at that point.

Representing Electric Fields

• Electric field lines show the direction and strength of the electric field.
• The strength of the electric field is proportional to the number of field lines per unit area.
• Field lines are closer together where the field is stronger.

Electric Fields Around Different Charge Configurations

• For a positive charge, the electric field lines point away from the charge.
• For a negative charge, the electric field lines point towards the charge.
• For two unlike charges, the electric field lines start from the positive charge and end at the negative charge.
• For two like charges, the electric field lines repel from both charges.

Electric Field Strength

• The electric field strength is defined as the force per unit charge that a test charge would experience at a point.
• The electric field strength is proportional to the force and inversely proportional to the charge.
• The units of electric field strength are newtons per coulomb (N·C^{-1}).

8 Electromagnetism

8.1 Magnetic Field Associated with a Current

• A current-carrying wire generates a magnetic field around the wire.
• The magnetic field lines are oriented perpendicular to the direction of the current flow.
• The direction of the magnetic field can be determined using the Right Hand Rule.
• The strength of the magnetic field is proportional to the current.

Visualizing Magnetic Fields

• The magnetic field around a wire can be visualized as concentric circles with the wire at the center.
• The magnetic field lines form a pattern that converges through the loop, creating a magnetic dipole with a distinct north and south pole.

Real-World Applications

• Electromagnets are devices that generate a magnetic field when an electric current flows through a coil of wire.
• Electromagnets are used in various applications such as electric motors, generators, relays, and magnetic storage devices.
• Overhead power lines carrying electric current generate magnetic fields, which can impact the environment.

8.2 Faraday's Law of Electromagnetic Induction

Current Induced by a Changing Magnetic Field

• Faraday's Law of Electromagnetic Induction states that a changing magnetic field induces an electric field.
• The induced emf is proportional to the rate of change of the magnetic flux.

Magnetic Flux

• Magnetic flux is the amount of magnetic field that passes through a surface.
• The magnetic flux is proportional to the magnetic field strength and the area of the surface.

Faraday's Law of Electromagnetic Induction

• The induced emf is proportional to the rate of change of the magnetic flux.
• The direction of the induced emf is determined by the direction of the changing magnetic field.

Direction of Induced Current

• The induced current in a conductor always opposes the change in magnetic flux.
• The direction of the induced current is determined by the Right Hand Rule.

Induction

• Electromagnetic induction is utilized in various applications, most notably in electrical generators.
• Self-induction occurs when a changing magnetic field produced by a changing current in a wire induces a voltage along the same wire.

Lenz's Law

• Lenz's Law states that the induced current will create a magnetic field that opposes the change in the magnetic flux.

9 Electric Circuits

9.1 Ohm's Law

• Ohm's Law states that the amount of electric current through a metal conductor at a constant temperature is proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.
• The resistance of the conductor is constant, independent of the voltage applied across it or current passed through it.
• Ohm's Law is a linear relationship between voltage and current.### Electrical Conductors and Resistors
• Ohmic conductors: have a linear relationship between current and voltage, and their resistance remains constant
  • Examples: circuit resistors, nichrome wire
• Non-ohmic conductors: do not have a linear relationship between current and voltage, and their resistance changes with temperature
  • Examples: light bulbs, diodes, transistors

Series and Parallel Circuits

• Series circuits: have only one path for current to flow, and the total resistance is the sum of individual resistances
  • Total resistance (Rs) = R1 + R2 + ... + Rn
  • Current is the same through all components
  • Voltage across each resistor is proportional to its resistance
• Parallel circuits: have multiple paths for current to flow, and the total resistance is less than the smallest individual resistance
  • Total resistance (Rp) = 1/(1/R1 + 1/R2 + ... + 1/Rn)
  • Voltage is the same across all components
  • Total current is the sum of currents through each parallel path

Power and Energy

• Power (P) is the rate at which work is done, measured in joules per second (J/s or watts, W)
  • P = I × V (power is directly proportional to both current and voltage)
  • P = I² × R (power is directly proportional to the square of current multiplied by resistance)
  • P = V² / R (power is directly proportional to the square of voltage divided by resistance)
• Energy (E) is the total amount of work done, measured in joules (J)
  • E = P × t (energy is the product of power and time)
  • 1 kilowatt-hour (kWh) = 1 kilowatt (kW) × 1 hour

Chemical Bonds

• Atoms form bonds to achieve a more stable electron configuration, similar to the noble gases
• Valence electrons are the outermost energy level electrons involved in bonding
• Lewis diagrams and spectroscopic notation are used to represent electron configurations

Covalent Bonds

• Formed when pairs of electrons are shared between atoms
• Types of covalent bonds:
  • Single bonds: one pair of electrons shared
  • Double bonds: two pairs of electrons shared
  • Triple bonds: three pairs of electrons shared
• Coordinate (dative) covalent bonds: both electrons in the bond come from the same atom

Molecular Shape

• Molecular shape determines how molecules interact and react with other molecules
• Valence shell electron pair repulsion (VSEPR) theory predicts molecular shape
• Steps to predict molecular shape:
  1. Draw the Lewis diagram
  2. Count electron pairs
  3. Determine basic geometry
  4. Write the final answer
• Examples of molecular shapes:
  • BeCl₂: linear
  • BF₃: trigonal planar
  • NH₃: trigonal pyramidal

Electronegativity

• Electronegativity is the ability of an atom to attract electrons towards itself
• Importance of electronegativity:
  • Influences the nature of bonds between atoms
  • Affects the polarity of molecules
  • Determines the solubility, melting points, and boiling points of molecules
• Calculating electronegativity differences:
  1. Identify the electronegativity values of the two atoms
  2. Subtract the smaller value from the larger value
• Electronegativity and bonding:
  • Non-polar covalent bond: electronegativity difference is 0
  • Weak polar covalent bond: electronegativity difference between 0.1 and 1
  • Strong polar covalent bond: electronegativity difference between 1.1 and 2
  • Ionic bond: electronegativity difference greater than 2.1

Energy and Bonding

• Bond length is the distance between the nuclei of two adjacent atoms when they form a bond
• Bond energy is the amount of energy required to break a bond between two atoms
• Factors influencing bond strength:
  • Bond length
  • Atom size
  • Number of bonds
• Energy changes in bond formation:
  • Decreasing energy: attractive forces dominate
  • Minimum energy point: bond formation
  • Increasing energy: repulsive forces dominate
• Graphical representation of energy changes:
  • Energy minimum (X): bond formation
  • Energy increase beyond X: repulsive forces dominate### Hydrogen Bonds
• Hydrogen bonds occur in molecules where hydrogen is covalently bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine.
• Hydrogen bonds are a relatively strong intermolecular force that forms between the hydrogen atom of one molecule and the electronegative atom of another molecule.
• Example: Water molecules form hydrogen bonds between the hydrogen atom of one molecule and the oxygen atom of another.

Intermolecular and Interatomic Forces

• Intermolecular forces occur between molecules and include dipole-dipole forces, hydrogen bonds, and London dispersion forces.
• Interatomic forces occur within molecules and include covalent, ionic, and metallic bonds.
• Interatomic forces are stronger than intermolecular forces.

Properties Affected by Intermolecular Forces

• Phase of Matter: Strong intermolecular forces result in solids, while weak intermolecular forces result in gases.
• Melting and Boiling Points: Substances with strong intermolecular forces have high melting and boiling points, while substances with weak intermolecular forces have low melting and boiling points.
• Viscosity: Substances with strong intermolecular forces are more viscous.
• Density: Solids are often the densest phase due to strong intermolecular forces.
• Thermal Expansion: As substances are heated, their molecules move more vigorously and expand.
• Thermal Conductivity: Metals have high thermal conductivity due to free electrons.

Investigation of Intermolecular Forces

• Evaporation: Substances with weaker intermolecular forces evaporate faster.
• Surface Tension: Stronger intermolecular forces result in higher surface tension.
• Solubility: Substances dissolve in solvents with similar intermolecular forces.
• Boiling Point: Substances with strong intermolecular forces have higher boiling points.
• Capillarity: Substances with strong intermolecular forces travel further up a narrow tube.

Molecular Size and Intermolecular Forces

• Larger molecules have stronger intermolecular forces.
• In organic compounds like alkanes, increasing the number of carbon atoms increases the boiling point and melting point due to stronger intermolecular forces.

The Chemistry of Water

• The unique microscopic structure of water is due to its polar nature, molecular shape, and intermolecular forces.
• Water molecules are held together by hydrogen bonds, which are responsible for many of its unique properties.

Unique Properties of Water

• Specific Heat: Water has a high specific heat, meaning it absorbs a lot of energy before its temperature changes significantly.
• Absorption of Infra-Red Radiation: Water can absorb infra-red radiation from the sun, acting as a heat reservoir and helping to moderate the Earth's climate.
• Melting Point and Boiling Point: Water has a melting point of 0°C and a boiling point of 100°C at standard pressure, allowing it to exist as a liquid over a wide range of temperatures.
• High Heat of Vaporisation: Water has a high heat of vaporisation, meaning a significant amount of energy is required to change water from liquid to gas.
• Less Dense Solid Phase: Water is less dense in its solid phase (ice) than in its liquid phase, which is crucial for maintaining liquid water on Earth and supporting aquatic life.

The Interactions of Water with Various Substances

• Water is an excellent solvent for many ionic and polar substances due to its polarity and hydrogen bonding.
• Water dissolves ionic compounds by surrounding the positive and negative ions with water molecules, stabilizing the ions in solution.
• Water dissolves many polar covalent compounds due to hydrogen bonding.
• Non-polar substances do not dissolve well in water due to the lack of attraction between water molecules and non-polar molecules.
• Water's solvent properties are essential for biological functions, nutrient transport, and environmental processes.

7 Electrostatics

7.1 Coulomb's Law

• Like charges repel each other, while unlike charges attract each other.
• The electrostatic force between charges increases when the magnitude of the charges increases or the distance between the charges decreases.
• Coulomb's law states that the magnitude of the electrostatic force between two point-like charges is inversely proportional to the square of the distance between the charges.
• The magnitude of the electrostatic force is proportional to the product of the charges.
• Coulomb's law is similar in form to Newton's universal law of gravitation, both are inverse-square laws.

7.2 Electric Field

Definition of Electric Field

• An electric field is a region of space in which an electric charge will experience a force.
• The direction of the electric field at a point is the direction of the force that a positive test charge would experience if placed at that point.

Representing Electric Fields

• Electric field lines show the direction and strength of the electric field.
• The strength of the electric field is proportional to the number of field lines per unit area.
• Field lines are closer together where the field is stronger.

Electric Fields Around Different Charge Configurations

• For a positive charge, the electric field lines point away from the charge.
• For a negative charge, the electric field lines point towards the charge.
• For two unlike charges, the electric field lines start from the positive charge and end at the negative charge.
• For two like charges, the electric field lines repel from both charges.

Electric Field Strength

• The electric field strength is defined as the force per unit charge that a test charge would experience at a point.
• The electric field strength is proportional to the force and inversely proportional to the charge.
• The units of electric field strength are newtons per coulomb (N·C^{-1}).

8 Electromagnetism

8.1 Magnetic Field Associated with a Current

• A current-carrying wire generates a magnetic field around the wire.
• The magnetic field lines are oriented perpendicular to the direction of the current flow.
• The direction of the magnetic field can be determined using the Right Hand Rule.
• The strength of the magnetic field is proportional to the current.

Visualizing Magnetic Fields

• The magnetic field around a wire can be visualized as concentric circles with the wire at the center.
• The magnetic field lines form a pattern that converges through the loop, creating a magnetic dipole with a distinct north and south pole.

Real-World Applications

• Electromagnets are devices that generate a magnetic field when an electric current flows through a coil of wire.
• Electromagnets are used in various applications such as electric motors, generators, relays, and magnetic storage devices.
• Overhead power lines carrying electric current generate magnetic fields, which can impact the environment.

8.2 Faraday's Law of Electromagnetic Induction

Current Induced by a Changing Magnetic Field

• Faraday's Law of Electromagnetic Induction states that a changing magnetic field induces an electric field.
• The induced emf is proportional to the rate of change of the magnetic flux.

Magnetic Flux

• Magnetic flux is the amount of magnetic field that passes through a surface.
• The magnetic flux is proportional to the magnetic field strength and the area of the surface.

Faraday's Law of Electromagnetic Induction

• The induced emf is proportional to the rate of change of the magnetic flux.
• The direction of the induced emf is determined by the direction of the changing magnetic field.

Direction of Induced Current

• The induced current in a conductor always opposes the change in magnetic flux.
• The direction of the induced current is determined by the Right Hand Rule.

Induction

• Electromagnetic induction is utilized in various applications, most notably in electrical generators.
• Self-induction occurs when a changing magnetic field produced by a changing current in a wire induces a voltage along the same wire.

Lenz's Law

• Lenz's Law states that the induced current will create a magnetic field that opposes the change in the magnetic flux.

9 Electric Circuits

9.1 Ohm's Law

• Ohm's Law states that the amount of electric current through a metal conductor at a constant temperature is proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.
• The resistance of the conductor is constant, independent of the voltage applied across it or current passed through it.
• Ohm's Law is a linear relationship between voltage and current.### Electrical Conductors and Resistors
• Ohmic conductors: have a linear relationship between current and voltage, and their resistance remains constant
  • Examples: circuit resistors, nichrome wire
• Non-ohmic conductors: do not have a linear relationship between current and voltage, and their resistance changes with temperature
  • Examples: light bulbs, diodes, transistors

Series and Parallel Circuits

• Series circuits: have only one path for current to flow, and the total resistance is the sum of individual resistances
  • Total resistance (Rs) = R1 + R2 + ... + Rn
  • Current is the same through all components
  • Voltage across each resistor is proportional to its resistance
• Parallel circuits: have multiple paths for current to flow, and the total resistance is less than the smallest individual resistance
  • Total resistance (Rp) = 1/(1/R1 + 1/R2 + ... + 1/Rn)
  • Voltage is the same across all components
  • Total current is the sum of currents through each parallel path

Power and Energy

• Power (P) is the rate at which work is done, measured in joules per second (J/s or watts, W)
  • P = I × V (power is directly proportional to both current and voltage)
  • P = I² × R (power is directly proportional to the square of current multiplied by resistance)
  • P = V² / R (power is directly proportional to the square of voltage divided by resistance)
• Energy (E) is the total amount of work done, measured in joules (J)
  • E = P × t (energy is the product of power and time)
  • 1 kilowatt-hour (kWh) = 1 kilowatt (kW) × 1 hour

Chemical Bonds

• Atoms form bonds to achieve a more stable electron configuration, similar to the noble gases
• Valence electrons are the outermost energy level electrons involved in bonding
• Lewis diagrams and spectroscopic notation are used to represent electron configurations

Covalent Bonds

• Formed when pairs of electrons are shared between atoms
• Types of covalent bonds:
  • Single bonds: one pair of electrons shared
  • Double bonds: two pairs of electrons shared
  • Triple bonds: three pairs of electrons shared
• Coordinate (dative) covalent bonds: both electrons in the bond come from the same atom

Molecular Shape

• Molecular shape determines how molecules interact and react with other molecules
• Valence shell electron pair repulsion (VSEPR) theory predicts molecular shape
• Steps to predict molecular shape:
  1. Draw the Lewis diagram
  2. Count electron pairs
  3. Determine basic geometry
  4. Write the final answer
• Examples of molecular shapes:
  • BeCl₂: linear
  • BF₃: trigonal planar
  • NH₃: trigonal pyramidal

Electronegativity

• Electronegativity is the ability of an atom to attract electrons towards itself
• Importance of electronegativity:
  • Influences the nature of bonds between atoms
  • Affects the polarity of molecules
  • Determines the solubility, melting points, and boiling points of molecules
• Calculating electronegativity differences:
  1. Identify the electronegativity values of the two atoms
  2. Subtract the smaller value from the larger value
• Electronegativity and bonding:
  • Non-polar covalent bond: electronegativity difference is 0
  • Weak polar covalent bond: electronegativity difference between 0.1 and 1
  • Strong polar covalent bond: electronegativity difference between 1.1 and 2
  • Ionic bond: electronegativity difference greater than 2.1