Physics and Chemistry Exam Guidelines

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Questions and Answers

Papers 1 and 2 contain questions across three cognitive levels.

False (B)

The total marks for Paper 2 in Chemistry is 150.

True (A)

The weight of remembering in Paper 1 is 5%.

False (B)

The duration for completing both papers is the same, which is 3 hours.

<p>True (A)</p> Signup and view all the answers

In Physics, the weight for applying and analyzing questions is 40%.

<p>True (A)</p> Signup and view all the answers

The Mechanics section in Paper 1 accounts for 75 marks.

<p>False (B)</p> Signup and view all the answers

The skills in Physical Sciences include forming an investigative question.

<p>True (A)</p> Signup and view all the answers

In Paper 2, the matter and materials section has a weight of 58 marks.

<p>True (A)</p> Signup and view all the answers

Mass is defined as the product of an object's weight and its acceleration due to gravity.

<p>False (B)</p> Signup and view all the answers

Momentum is a vector quantity that has the same direction as the velocity of the object.

<p>True (A)</p> Signup and view all the answers

Newton's second law in terms of momentum states that force is equal to the mass times the speed of an object.

<p>False (B)</p> Signup and view all the answers

Impulse is calculated using the time for which a net force acts on an object multiplied by the change in momentum.

<p>False (B)</p> Signup and view all the answers

An example of a situation that increases momentum is when a soccer ball is kicked in the direction it is already moving.

<p>True (A)</p> Signup and view all the answers

Weightlessness occurs when the gravitational force acting on an object is infinitely large.

<p>False (B)</p> Signup and view all the answers

The momentum of an object can be defined as the sum of all forces acting on it.

<p>False (B)</p> Signup and view all the answers

Inelastic collisions conserve momentum and kinetic energy.

<p>False (B)</p> Signup and view all the answers

An atomic absorption spectrum is created when an atom transitions from a lower energy state to a higher energy state.

<p>False (B)</p> Signup and view all the answers

When light passes through a cold gas, it produces a continuous spectrum with dark lines.

<p>True (A)</p> Signup and view all the answers

An atomic emission spectrum contains only dark lines and is continuous in nature.

<p>False (B)</p> Signup and view all the answers

1 mole of any gas occupies 22.4 dm3 at standard temperature and pressure.

<p>True (A)</p> Signup and view all the answers

The conservation of mass implies that the total mass of reactants equals the total mass of products in a balanced chemical equation.

<p>True (A)</p> Signup and view all the answers

Under identical conditions of temperature and pressure, different gases occupy different volumes even if their moles are equal.

<p>False (B)</p> Signup and view all the answers

In stoichiometric calculations, the empirical formula represents the actual number of atoms in a molecule.

<p>False (B)</p> Signup and view all the answers

The percentage yield of a chemical reaction can be calculated through stoichiometric methods.

<p>True (A)</p> Signup and view all the answers

Endothermic reactions are characterized by ΔH > 0.

<p>True (A)</p> Signup and view all the answers

Exothermic reactions require energy input to proceed.

<p>False (B)</p> Signup and view all the answers

Activation energy is the maximum energy required for a reaction to occur.

<p>False (B)</p> Signup and view all the answers

The reaction rate is defined as the change in concentration of reactants or products over time.

<p>True (A)</p> Signup and view all the answers

A catalyst increases the activation energy of a reaction.

<p>False (B)</p> Signup and view all the answers

In a potential energy versus course of reaction graph, an endothermic reaction will have a downward slope.

<p>False (B)</p> Signup and view all the answers

The collision theory states that a reaction occurs when particles collide with sufficient energy.

<p>True (A)</p> Signup and view all the answers

The nature of reactants does not influence the rate of chemical reactions.

<p>False (B)</p> Signup and view all the answers

As the concentration of reactant ions increases, the potential difference of a galvanic cell (Vcell) increases.

<p>False (B)</p> Signup and view all the answers

The direction of electron flow in a galvanic cell is from the oxidizing agent to the reducing agent.

<p>False (B)</p> Signup and view all the answers

The salt bridge in a galvanic cell serves to complete the circuit by allowing the movement of ions between the two half-cells.

<p>True (A)</p> Signup and view all the answers

A half-cell that undergoes oxidation will have a higher standard reduction potential than one that undergoes reduction.

<p>False (B)</p> Signup and view all the answers

Cell notation for an inert electrode includes the species involved along with the inert material.

<p>True (A)</p> Signup and view all the answers

The overall cell reaction in a galvanic cell is obtained by combining the oxidation and reduction half-reactions.

<p>True (A)</p> Signup and view all the answers

The emf of a standard galvanic cell will be negative if the reaction is spontaneous under standard conditions.

<p>False (B)</p> Signup and view all the answers

Galvanic cells achieve equilibrium when the Vcell is equal to 0.

<p>True (A)</p> Signup and view all the answers

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Study Notes

Examination Guidelines

  • Papers 1 and 2 include questions across four cognitive levels:
    • Remembering (Recall) - 15%
    • Understanding (Comprehension) - 35% to 40%
    • Applying and Analysing - 40% to 35%
    • Evaluating and Creating (Synthesis) - 10%

Paper 1: Physics Focus

  • Total marks for Paper 1: 150
  • Duration: 3 hours
  • Content:
    • Mechanics - 65 marks
    • Waves, Sound and Light - 15 marks
    • Electricity and Magnetism - 55 marks
    • Matter and Materials - 15 marks

Paper 2: Chemistry Focus

  • Total marks for Paper 2: 150
  • Duration: 3 hours
  • Content:
    • Chemical Change - 92 marks
    • Matter and Materials - 58 marks

Skills in Physical Sciences

  • Identify and Question Phenomena: Formulate an investigative question that probes the relationship between mass and weight; Explain the concept of weightlessness

Momentum and Impulse

  • Momentum:
    • Defined as the product of mass and velocity.
    • Linear momentum is a vector quantity and has the same direction as the velocity.
    • Momentum can be calculated using the formula: p = mv.
    • Can be illustrated using vector diagrams, showing the relationship between initial, final, and change in momentum.
  • Newton's Second Law of Motion in terms of Momentum:
    • The net force acting on an object equals the rate of change of the object's momentum in the direction of the force.
    • Expressed in symbols: Fnet = Δp/Δt
    • The relationship between net force and change in momentum can be explained in various situations involving changes in velocity, like increasing, decreasing, or reversing directions.
  • Impulse:
    • Defined as the product of the net force acting on an object and the time the net force acts.
    • The Impulse-momentum theorem (FnetΔt = mΔv) can be used to calculate:
      • Resultant force
      • Time the force is applied
      • Change in momentum
    • Impulse explains safety considerations in everyday life, such as airbags, seatbelts, and arrestor beds.
  • Conservation of Momentum:
    • A system in physics implies a collection of objects that interact with each other.
    • In a closed system, the total momentum remains constant.
    • This conservation principle applies during collisions (elastic or inelastic).

Emission and Absorption Spectra

  • Atomic spectra originate from energy transitions within atoms.
  • Atomic Absorption Spectrum:
    • Occurs when electromagnetic radiation passing through a substance is absorbed.
    • For example, when light passes through a cold gas, atoms absorb characteristic frequencies and dark lines appear on a continuous spectrum.
    • The frequencies of absorption lines are unique to the specific atom in the gas.
  • Atomic Emission Spectrum:
    • Formed due to an atom transitioning from a higher to a lower energy state, emitting electromagnetic radiation.
    • For example, atoms in a hot gas emit light at characteristic frequencies, creating a line spectrum with colored lines specific to the emitting atoms.
    • The frequencies of emission lines are unique to the type of atom emitting them.

Paper 2: Chemistry

Representing Chemical Change

  • Balanced Chemical Equations:
    • Represent chemical reactions using chemical formulas, symbols, and coefficients.
    • Equations should be balanced to ensure the conservation of atoms and mass.
    • Interpreting balanced equations involves understanding the conservation of atoms and mass.

Quantitative Aspects of Chemical Change

  • Molar Volume of Gases:
    • One mole of any gas occupies 22.4 dm3 at 0 °C (273 K) and 1 atmosphere (101.3 kPa).
  • Volume Relationships in Gaseous Reactions:
    • Balanced equations can be interpreted in terms of volume relationships for gases under the same temperature and pressure.
    • Equal moles of different gases occupy the same volume.
  • Concentration of Solutions:
    • Calculate the molar concentration of a solution.
  • More Complex Stoichiometric Calculations:
    • Determine the empirical and molecular formulas of compounds.
    • Calculate percentage yield in a chemical reaction: actual yield / theoretical yield * 100%.

Energy and Change

  • Energy Changes in Reactions related to Bond Energy Changes:
    • Heat of reaction (ΔH): Energy absorbed or released in a chemical reaction.
    • Exothermic reactions: Reactions that release energy (ΔH < 0).
    • Endothermic reactions: Reactions that absorb energy (ΔH > 0).
    • Classify reactions as exothermic or endothermic.
  • Activation Energy:
    • Minimum energy required for a reaction to occur.
    • Activated complex: Unstable transition state between reactants and products.
    • Potential energy versus course of reaction graphs can be used to illustrate:
      • Catalysed and uncatalysed reactions
      • Endothermic and exothermic reactions

Rate and Extent of Reaction

  • Rates of Reaction and Factors Affecting Rate:
    • Reaction rate: Change in concentration of reactants or products per time unit.
    • Calculate reaction rates using the equation: Rate = Δc/Δt (units: mol∙dm-3∙s-1)
    • Factors influencing reaction rates:
      • Nature of reacting substances
      • Surface area
      • Concentration (pressure for gases)
      • Temperature
      • Presence of a catalyst
    • Collision theory: Explains reaction rate as a result of particles colliding with sufficient energy to form products.
  • Relationship between Current, Potential Difference, Rate, and Equilibrium:
    • The potential difference (Vcell) in a galvanic cell is related to the extent the spontaneous cell reaction has reached equilibrium.
    • The relationship between Vcell and the concentration of product and reactant ions is qualitative.
    • Vcell decreases as the concentration of product ions increases and reactant ions decrease until equilibrium is reached (Vcell = 0, "flat cell").
  • Understanding Processes and Redox Reactions in Galvanic Cells:
    • Describe the movement of ions in the solutions.
    • State the direction of electron flow through the external circuit.
    • Write the half-reactions occurring at the electrodes.
    • State the function of the salt bridge.
    • Use cell notation or diagrams to represent galvanic cells.
    • Use standard reduction potentials to calculate the emf of a standard galvanic cell.
    • A positive value of the standard emf indicates a spontaneous reaction under standard conditions.

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