Year 10 - Science
pH scale and indicators
Making salts
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
This unit explores empirical formulae, balanced chemical and ionic equations, gas identification, acid reactions, and pH as a measure of hydrogen ion concentration. It covers separation techniques and focuses on planning experiments, accurate measurements, safety, and communicating findings.
Lesson Summary
You will learn to explain the pH scale and appropriately use universal indicator, phenolphthalein, methyl orange, and litmus and pH meters to identify different solutions.
Key Notes
- The pH scale ranges from 0 to 14, indicating how acidic or basic a substance is.
- Universal indicator provides a full range of colours corresponding to different pH levels, and this can be a limitation.
- Phenolphthalein changes from colourless to pink in alkaline conditions.
- Methyl orange shifts from red in acidic conditions to yellow in basic conditions.
- Litmus paper turns red in acidic conditions and blue in basic conditions, the solution will be purple when neutral.
Vocabulary To Learn
- pH scale: a scale of acidity or alkalinity, often shown to be between values of 0 and 14
- indicator: a solution or paper which will change a different colour depending on pH of a solution
- pH meter: an electric device which measures pH and provides a value after being calibrated with reference samples
- acidity: the concentration of hydrogen ions (H⁺) present in a solution; acids have a pH value less than 7
- alkalinity: the concentration of hydroxide ions (OH⁻) present in a solution; alkalis have a pH value greater than 7
Common Mistakes To Avoid
- All indicators provide precise pH values and give the same information as pH meters.
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
The pH scale ranges from 0 to 14, indicating how acidic or basic a substance is. Universal indicator provides a full range of colours corresponding to different pH levels, and this can be a limitation.
2. Define this scientific word and use it in context. 'pH scale'
a scale of acidity or alkalinity, often shown to be between values of 0 and 14. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: All indicators provide precise pH values and give the same information as pH meters. Correction: Indicators do not provide exact pH values; they only indicate whether a solution is acidic, neutral, or alkaline by changing colour. A pH meter, on the other hand, measures the exact pH value of a solution and is more accurate.
More Lessons In This Unit
- Acid-base reactions Study Guide
- Acid-base reactions (carbonates as bases) Study Guide
- Adapting a multistep chemical procedure for making a pure dry salt Study Guide
- Change in pH: practical Study Guide
- Chemical reactions of acids with metals and metal carbonates Study Guide
- Comparing concentration with strength Study Guide
- Concentration of solutions Study Guide
- Concentration of solutions: using moles Study Guide
- Concentration of solutions: using moles (RAM 1 d.p.) Study Guide
- Describing salts Study Guide
- Hazard symbols and equipment Study Guide
- Ionic equations: salt formation Study Guide
- Making a pure dry sample of a soluble salt Study Guide
- Solubility rules Study Guide
- Titrations: analytical technique Study Guide
- Titrations: calculating an unknown concentration Study Guide
- Titrations: calculating an unknown concentration (RAM 1 d.p.) Study Guide
- Titrations: making soluble salts Study Guide
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