chemistry paper 1

Describe the structure of an atom, including the relative charges and masses of protons, neutrons, and electrons

Nucleus with protons (+1 charge, mass 1) and neutrons (0 charge, mass 1); electrons orbit with –1 charge and negligible

Compare ionic, covalent, and metallic bonding

Ionic = electron transfer between ions; covalent = shared electron pairs; metallic = delocalised electrons around positive ions

Explain why ionic compounds have high melting and boiling points

Strong electrostatic forces between oppositely charged ions require lots of energy to break

Describe diamond’s structure and relate it to its properties

Giant covalent lattice, each carbon bonded to 4 others; extremely hard and high melting point; does not conduct electricity

Explain why graphite conducts electricity and is slippery

Layered structure with delocalised electrons; layers slide over each other

Define a mole and Avogadro’s constant

A mole = 6.02×10²³ particles (Avogadro's constant)

Calculate moles using mass ÷ Mr (e.g., 36 g H₂O → 2 mol).

36 ÷ 18 = 2 mol

Define empirical formula and describe how to calculate it from masses

Simplest whole-number ratio of atoms; convert mass → moles → divide by smallest mole value

What is a limiting reactant?

The reactant used up first, limiting how much product forms

How do you calculate percentage yield?

(Actual yield ÷ theoretical yield) × 100%

Describe the reactivity series and its use in predicting displacement reactions

Series ranks metals by reactivity (K > Na… Au); a more reactive metal displaces a less reactive one from a compound

Write the ionic equation for Mg + Cu²⁺ → Mg²⁺ + Cu

Mg → Mg²⁺ + 2e⁻ And Cu²⁺ + 2e⁻ → Cu

Write half-equations for electrolysing molten PbBr₂

Pb²⁺ + 2e⁻ → Pb (cathode); 2Br⁻ → Br₂ + 2e⁻ (anode)

Describe the electrolysis of aqueous CuSO₄ at electrodes

Cu²⁺ + 2e⁻ → Cu at cathode; 4OH⁻ → O₂ + 2H₂O + 4e⁻ at anode

Why is cryolite used in the extraction of aluminium?

Lowers the melting point of aluminium oxide, reducing energy costs

Define exothermic and endothermic reactions with an example

Exothermic releases energy (e.g., combustion); endothermic absorbs energy (e.g., thermal decomposition).

Explain activation energy with reference to an energy profile diagram

The minimum energy needed for a reaction; represented as the energy peak between reactants and products.

How do catalysts speed up reactions (collison theory)?

Provide alternate pathway with lower activation energy, increasing frequency of successful collisions

Name 4 factors affecting reaction rate

Temperature, concentration, surface area, and catalysts

Describe how to measure temperature change in a neutralisation reaction

Mix fixed volumes of acid and alkali, record temp change with a thermometer or probe

Describe the structure of an atom, including the relative charges and masses of protons, neutrons, and electrons

Nucleus with protons (+1 charge, mass 1) and neutrons (0 charge, mass 1); electrons orbit with 1 charge and negligible

Compare ionic, covalent, and metallic bonding

Ionic = electron transfer between ions; covalent = shared electron pairs; metallic = delocalised electrons around positive ions

Explain why ionic compounds have high melting and boiling points

Strong electrostatic forces between oppositely charged ions require lots of energy to break

Describe diamond’s structure and relate it to its properties

Giant covalent lattice, each carbon bonded to 4 others; extremely hard and high melting point; does not conduct electricity

Explain why graphite conducts electricity and is slippery

Layered structure with delocalised electrons; layers slide over each other

Define a mole and Avogadro’s constant

A mole = 6.02\times10^{23} particles (Avogadro's constant)

Calculate moles using mass \div Mr (e.g., 36\text{ g} H2O \to 2\text{ mol}).

36 \div 18 = 2\text{ mol}

Define empirical formula and describe how to calculate it from masses

Simplest whole-number ratio of atoms; convert mass \to moles \to divide by smallest mole value

What is a limiting reactant?

The reactant used up first, limiting how much product forms

How do you calculate percentage yield?

(\text{Actual yield} \div \text{theoretical yield}) \times 100\%

Describe the reactivity series and its use in predicting displacement reactions

Series ranks metals by reactivity (K > Na… Au); a more reactive metal displaces a less reactive one from a compound

Write the ionic equation for \text{Mg} + \text{Cu}^{2+} \to \text{Mg}^{2+} + \text{Cu}

\text{Mg} \to \text{Mg}^{2+} + 2\text{e}^- And \text{Cu}^{2+} + 2\text{e}^- \to \text{Cu}

Write half-equations for electrolysing molten PbBr2

\text{Pb}^{2+} + 2\text{e}^- \to \text{Pb} (cathode); 2\text{Br}^- \to \text{Br}_2 + 2\text{e}^- (anode)

Describe the electrolysis of aqueous CuSO4 at electrodes

\text{Cu}^{2+} + 2\text{e}^- \to \text{Cu} at cathode; 4\text{OH}^- \to \text{O}2 + 2\text{H}2\text{O} + 4\text{e}^- at anode

Why is cryolite used in the extraction of aluminium?

Lowers the melting point of aluminium oxide, reducing energy costs

Define exothermic and endothermic reactions with an example

Exothermic releases energy (e.g., combustion); endothermic absorbs energy (e.g., thermal decomposition).

Explain activation energy with reference to an energy profile diagram

The minimum energy needed for a reaction; represented as the energy peak between reactants and products.

How do catalysts speed up reactions (collison theory)?

Provide alternate pathway with lower activation energy, increasing frequency of successful collisions

Name 4 factors affecting reaction rate

Temperature, concentration, surface area, and catalysts

Describe how to

Mix fixed volumes of acid and alkali, record temp change with a thermometer or probe