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9.3.1Transport in Animals

Chemical Cells — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 4 parts Lesson 8 of 8 Unit quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
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Part 1 of 4Structure of a Simple Cell

A simple cell needs only two electrodes, an electrolyte and an external circuit.

Electrodes
  • Electrodes Two electrodes made of metals with different reactivities are immersed in an electrolyte.
Electrolyte
  • Electrolyte The electrolyte contains ions that move between the electrodes and complete the circuit.
External circuit
  • External circuit A wire connects the electrodes to a voltmeter, so that electrons can flow around the circuit.
Energy conversion
  • Energy conversion A chemical cell converts chemical energy from a reaction into electrical energy.

Part 2 of 4How the Voltage Is Produced

Zinc and copper is the standard example of this process.

1
The more reactive metal, zinc, releases electrons more readily and forms ions in the electrolyte.
2
The electrons left on the zinc electrode give it a negative charge.
3
Electrons flow through the wire to the less reactive copper electrode, which becomes the more positive electrode.
4
The difference in the ability of the two electrodes to release electrons creates the voltage.

Part 3 of 4Factors Affecting the Voltage

Choosing the metals and electrolyte controls the size of the voltage.

Factors Affecting the Voltage
Metal reactivity
  • Metal reactivity A greater difference in reactivity between the two metals gives a greater voltage.
Metal pair
  • Metal pair Magnesium and copper are further apart in the reactivity series than zinc and copper, so they give a larger voltage.
Electrolyte
  • Electrolyte Different electrolytes react with the electrodes in different ways, which changes the voltage.
Reactants
  • Reactants Some cells give a voltage only until their reactants are used up.

Part 4 of 4Exam Checklist & Tips

9.3.1 – Key Points for the Exam

  • Chemical cell A device that produces electrical energy from a chemical reaction between two different electrodes.
  • Electrolyte A liquid or solution containing mobile ions that conducts electricity.
  • Electrode A conductor through which electricity enters or leaves an electrolyte.
  • Potential difference The voltage produced between the two electrodes of a cell.

Common Mistakes

  • Confusing a chemical cell with an electrolytic cell, which uses electricity to break up a compound.
  • Saying the more reactive metal becomes the positive electrode; it becomes the negative electrode.
  • Stating that copper is the more reactive metal in a zinc and copper cell; zinc is more reactive.
  • Saying that electrons flow through the electrolyte;
    • electrons flow through the external wire, while ions move through the electrolyte.

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Cambridge 9700 AS Biology Core Formula

Magnification Triangle & Unit Conversion

Formula: M = I / A  ⇔  A = I / M  ⇔  I = M × A

Units: 1 mm = 1,000 μm = 1,000,000 nm.
Rule: Convert Image size (ruler mm) to μm by ×1,000 before dividing by Actual size.

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