Starter quiz
- What is the pH scale used to measure?
- the concentration of salts in a solution
- the colour of a solution
- the acidity or alkalinity of a solution ✓
- the temperature of a solution
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- What is ionisation?
- the process of dissolving a substance in water
- the release of energy in a reaction
- the mixing of acids and bases
- the formation of ions by gaining or losing electrons ✓
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- What is the charge of a hydrogen ion?
- negative
- neutral
- positive ✓
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- What does it mean if an acid is completely ionised in an aqueous solution?
- the acid has fully reacted with a base
- all acid molecules dissociate into ions ✓
- the acid becomes neutral
- the acid stops reacting
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- What does a weak acid do in an aqueous solution?
- it completely dissociates into ions
- it partially dissociates into ions ✓
- it does not ionise
- it becomes a strong base
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- What is the significance of titration curves?
- they show the temperature change during a reaction
- they indicate changes in volume
- they graph pH changes to find neutralisation points ✓
- they track time during a reaction
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Exit quiz
- Match the following key terms to their definitions.
- hydrogen ion (H⁺)⇔a positive ion formed when a hydrogen atom loses an electron ✓
- pH⇔the measure of hydrogen ion concentration in a solution ✓
- concentration⇔the amount of solute dissolved in a certain volume of solution ✓
- strong acid⇔an acid that fully dissociates to form H⁺ ions in aqueous solution ✓
- weak acid⇔an acid that partially dissociates to form H⁺ ions in aqueous solution ✓
- Which of the following statements about a strong acid in an aqueous solution is correct?
- It is partially ionised.
- It releases very few H⁺ ions.
- It is completely ionised. ✓
- It has a pH above 7.
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- Why do strong acids have a lower pH than weak acids of the same concentration?
- they contain more H⁺ ions ✓
- they contain fewer H⁺ ions
- they ionise partially
- they absorb more water
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- What happens to the pH of a solution if the hydrogen ion concentration increases by a factor of 10?
- the pH increases by 1
- the pH decreases by 1 ✓
- the pH increases by 10
- the pH decreases by 10
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- How can titration curves help chemists?
- they measure the temperature of a reaction
- they show the colour change in the solution
- they allow chemists to pinpoint an accurate end point ✓
- they help identify weak acids
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- What happens during the neutralisation of a weak acid?
- the pH decreases rapidly at first
- the pH stays constant throughout
- the pH changes gradually at the start ✓
- the pH changes quickly after the end point is reached
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Worksheet
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Presentation
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Lesson Details
Key learning points
- pH is a logarithmic scale (as hydrogen ion concentration increases by a factor of 10, the pH decreases by 1).
- For a given concentration, a stronger acid contains more H⁺ ions.
- Titration curves can be used to show the change in pH to allow chemists to pinpoint a more accurate end point.
- A strong acid is completely ionised in aqueous solution, a weak acid only partially ionises.
- Titration curves show how the pH changes throughout a neutralisation reaction.
Common misconception
Pupils often confuse the chemistry meaning of strong/weak and concentrated/dilute due to the use of these words in everyday conversation.
Clear definitions of the words are required with practice opportunities to recognise/describe whether the substances are strong or weak acids and if concentrated or dilute.
Keywords
Hydrogen ion - A positively charged ion formed when a hydrogen atom loses an electron (H⁺).
Ph - The measure of the hydrogen ion (H⁺) concentration of a solution.
Concentration - The amount of solute dissolved in a certain volume of solution.
Strong acid - An acid which fully dissociates to form H⁺ ions in aqueous solution.
Weak acid - An acid which partially dissociates to form H⁺ ions in aqueous solution.
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