Revision Booklet for Year 9 Higher - Paper 2

Section A - Chemistry

Group 7 Elements (Halogens)

• Definition: Group 7 elements are known as halogens.
• Electron Configuration: Each halogen has 7 electrons in their outer shell, which leads to similar reactivity.
• Physical Characteristics:
  • Halogens possess colored vapors.
  • They exist as diatomic molecules, meaning they consist of pairs of atoms.
  • Examples include:
  • Fluorine (F2)
  • Chlorine (Cl2)
  • Bromine (Br2)

Atomic Models

1. J.J. Thompson - Plum Pudding Model
   • Description: The atom is a ball of positive charge with electrons embedded within it.
   • Characteristics:
     • No empty space exists within the atom.
     • Mass is uniformly distributed throughout.
2. Niels Bohr - Bohr's Model
   • Description: Electrons orbit the nucleus in fixed paths.
   • Features: Electrons are found at specified distances from the nucleus.

Ionic Bonding

• Structure:
  • Ionic substances form a giant ionic lattice.
• Bonding:
  • Strong electrostatic forces hold oppositely charged ions together in all directions, known as ionic bonding.
• Sodium Chloride (NaCl):
  • General Description:
  • A metal atom transfers an electron to a non-metal atom.
  • The metal atom loses electrons, forming a positive ion.
  • The non-metal atom gains electrons, forming a negative ion.
• Magnesium to Iodine Reaction:
  • Magnesium (Mg) loses 2 electrons to form a positive ion (Mg²+).
  • Two iodine (I) atoms each gain one electron to form negative ions (I⁻).

Covalent Bonding

• Definition:
  • Occurs between two or more non-metals.
• Mechanism:
  • Atoms share pairs of electrons to form strong covalent bonds.
• Substance Types:
  • Covalent substances may consist of small molecules or could form giant covalent structures (e.g., diamond, silicon dioxide).
• Characteristics:
  • Covalent bonds do not involve charged ions.

Dot and Cross Diagrams for Small Molecules

• General Characteristics:
  • These diagrams illustrate the sharing of electrons in covalent bonds.
• Small Covalent Molecules:
  • Examples with diagrams include:
  • Hydrogen (H2)
  • Chlorine (Cl2)
  • Methane (CH4)
  • Ammonia (NH3)
  • Water (H2O)
  • Oxygen (O2)

Properties of Small Covalent Molecules

1. Physical State:
   • Generally gases or liquids with low melting and boiling points.
   • Explanation:
     • Small covalent molecules possess weak intermolecular forces.
     • Little energy is required to overcome these forces.
   • Larger molecules exhibit stronger intermolecular forces, resulting in higher melting and boiling points.
2. Electrical Conductivity:
   • Small covalent molecules do not conduct electricity.
   • Explanation:
     • Molecules lack an overall electric charge.

Giant Covalent Structures

Example: Diamond

• Structure and Bonding:
  • Formed solely from carbon atoms arranged in a regular tetrahedral network.
  • Each carbon atom bonds to four others without free (delocalized) electrons.
• Uses:
  • Applications include laser beams, cutting tools, drills, and jewelry.
• Properties of Diamond:

1. Hardness:
   • Diamond's hardness is due to its giant covalent structure and strong covalent bonding.
2. Electrical Conductivity:
   • Diamond does not conduct electricity owing to lack of delocalized electrons.
3. Melting Point:
   • High melting point due to strong covalent bonds requiring significant energy to break.

Polymers

• Definition:
  • Polymers are long-chain molecules made from many smaller units called monomers.
• Characteristics:
  • Composed of large molecules linked through strong covalent bonds.
  • Polymers typically have relatively strong intermolecular forces, making them solid at room temperature.
• Concerns with Synthetic Polymers:
  • Derived from non-renewable resources (crude oil).
  • High energy consumption during production.
  • Non-biodegradable, leading to landfill issues.

Section B - Physics

Circuit Symbols

• Various symbols are used to represent components in electrical circuits.

Scalars and Vectors

1. Scalars:
   • Scalars are quantities defined by magnitude alone without direction.
   • Examples include: mass, temperature, distance, time, speed, and energy.
2. Vectors:
   • Vectors possess both magnitude and direction.
   • Examples include: force, displacement, velocity, and acceleration.

Forces

• Definition:
  • A force can be classified as either a push or pull and is not visible but can be observed through its effects.
• **Effects of Forces on Objects: **
  • Can alter an object's speed, direction of movement, or shape (e.g., stretching an elastic band).
• Measurement:
  • Measured using a force meter (or newton meter).
  • The unit of measurement is Newton (N).

Types of Forces

1. Contact Forces:
   • Include friction, air resistance, tension, normal contact force (opposing gravity), forward force, and upthrust (buoyant force).
2. Non-contact Forces:
   • Include gravitational force, magnetic force, and electrostatic forces.

Changes in Energy Store

1. Kinetic Energy:
   • Calculated using the equation: $E_k = 0.5 imes m imes v^2$
     • Where:
     • Kinetic energy, $E_k$, is in joules (J)
     • Mass, $m$, is in kilograms (kg)
     • Speed, $v$, is in meters per second (m/s)
2. Elastic Potential Energy:
   • Calculated using the equation: $E_e = 0.5 imes k imes e^2$
     • Where:
     • Elastic potential energy, $E_e$, is in joules (J)
     • Spring constant, $k$, is in newtons per meter (N/m)
     • Extension, $e$, is in meters (m)
3. Gravitational Potential Energy:
   • Calculated using the equation: $E_p = m imes g imes h$
     • Where:
     • Gravitational potential energy, $E_p$, is in joules (J)
     • Mass, $m$, is in kilograms (kg)
     • Gravitational field strength, $g$, is in newtons per kilogram (N/kg)
     • Height, $h$, is in meters (m)

Worked Example

• Problem: A toast was raised by a spring and its change in gravitational potential energy was observed at 0.049 J with a mass of 0.050 kg in a gravitational field strength of 9.8 N/kg.

1. Identify Data:
   • $E_p = 0.049 J$
   • $m = 0.050 kg$
2. Write Equation:
   • $E_p = m imes g imes h$
3. Substitute Values:
   • $0.049 = 0.050 imes 9.8 imes h$
4. Solve for Height:
   • $h = \frac{0.049}{(0.050 imes 9.8)}$
5. Calculation:
   • Perform the calculation and include appropriate units.

Energy Resources

1. Non-renewable Resources:
   • Resources that cannot be replenished and will eventually deplete.
   • Examples:
     • Fossil Fuels (Coal, Oil, Natural Gas) - a chemical energy store.
     • Nuclear Power - energy derived from atomic structures.
     • Fossil Fuel Process:
     1. Combustion of fossil fuels generates steam.
     2. Steam drives turbines.
     3. Turbines spin generators, producing electricity.
     4. Transformers manage voltage levels entering the National Grid and homes.
   • Advantages and Disadvantages of Fossil Fuels:
     • Advantages:
     • Readily available.
     • Relatively easy energy production.
     • Disadvantages:
     • Finite resources leading to depletion.
     • Rising fuel costs.
     • Greenhouse gas emissions upon combustion (CO2).
2. Using Nuclear Power:
   • Process Overview:
     • Nuclear fission reactors utilize atomic nuclei processes but do not need in-depth understanding.
   • Advantages and Disadvantages of Nuclear Power:
     • Advantages:
     • No CO2 emissions upon operation.
     • Does not produce SO2, preventing acid rain.
     • 1 kg of uranium yields millions of times more energy than 1 kg of coal.
     • Disadvantages:
     • Non-renewable, will eventually deplete.
     • High initial and decommissioning costs.
     • Generates hazardous radioactive waste.
     • Potential release of radioactivity into the environment.
3. Renewable Resources:
   • Sources of energy that can be replenished.
   • Types:
     • Biomass - combusted living/dead materials.
     • Geothermal - energy from radioactive rocks.
     • Hydro Electric Power - gravitational energy from water in high locations.
     • Solar - heat and light from the sun for thermal and electrical energy.
     • Tidal - harnessing gravitational energy from the moon.
     • Wind - kinetic energy from air movement due to uneven heating.
     • Waves - energy from wind's effect on water.
   • Biofuels:
     • Fuels derived from plant matter (e.g., biodiesel, bioethanol).
   • Advantages and Disadvantages of Biofuels:
     • Advantages:
     • Renewable.
     • Lower carbon emissions during combustion.
     • Reduces reliance on fossil fuels.
     • Disadvantages:
     • Requires farmland used for food production.
     • High labor demands for production.
     • Requires engine modification for uses.
   • Energy from Wind:
     • Advantages and Disadvantages of Wind Power:
     • Advantages:
       • Renewable source.
       • Low operational costs.
     • Disadvantages:
       • High installation costs.
       • Creates visual pollution.
       • Noise pollution.
       • Reliability dependent on wind strength.
   • Energy from Water:
     • Water energy is derived from gravitational storage in high locations.
     • Types:
     • Tidal:
       • Utilizes the moon’s gravitational pull to generate energy through dam systems.
     • Hydro Electric:
       • Water from high reservoirs is allowed to flow downward through turbines.
     • Advantages and Disadvantages of Water Power:
     • Advantages:
       • Renewable.
       • Low operational costs.
       • No emissions.
     • Disadvantages:
       • Visual pollution.
       • Potential habitat destruction from flooding.
       • Could obstruct shipping routes.
   • Energy from the Sun:
     • Primary source of energy for all forms.
     • Advantages and Disadvantages of Solar Power:
     • Advantages:
       • Renewable.
       • Low service costs.
     • Disadvantages:
       • Low efficiency of solar cells.
       • High costs for efficiency improvements.
       • Weather dependency affects productivity.