3.1.4Physical Chemistry
Practical: Investigating Temperature Changes — Edexcel International GCSE Science Double Award 4SD0 - Chemistry Revision Notes & Topical Questions
5 min read 7 parts Lesson 5 of 19
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.
Part 1 of 5Aim and variables
Aim
- Aim To find how the temperature change in a neutralisation depends on the volume of alkali added to a fixed volume of acid.
Variables
- Variables Independent: volume of sodium hydroxide solution.
- Dependentmaximum temperature reached.
- Controlvolume and concentration of acid, concentration of alkali, starting temperature, same cup and lid.
Prediction
- Prediction The temperature should rise as more alkali is added, reach a peak at the volume that neutralises the acid,
- then fall as extra cold alkali only dilutes the mixture.
Part 2 of 5Method
1
Stand a polystyrene cup inside a beaker for support and insulation.
2
Measure 25 cm3 of 2 mol/dm3 hydrochloric acid with a measuring cylinder and pour it into the cup.
3
Record the temperature of the acid.
4
Add 5 cm3 of 2 mol/dm3 sodium hydroxide, fit the lid, and stir gently with the thermometer.
5
Record the highest temperature reached.
6
Repeat with fresh acid, adding 10, 15, 20 up to 40 cm3 of alkali each time.
7
Repeat the whole experiment and calculate mean maximum temperatures.
Part 3 of 5Processing the data
| Step | Action |
|---|---|
| Temperature change | Final maximum temperature − starting temperature |
| Mean | Add the repeat values and divide by the number of repeats; ignore anomalies |
| Graph | Plot volume of alkali (x-axis) against temperature change or maximum temperature (y-axis) |
| Lines of best fit | Draw two straight lines, one through the rising points and one through the falling points |
| Neutralisation point | Read off the volume at which the lines meet |
Part 4 of 5Improving reliability and accuracy
Sources of error
Heat loss
- Heat loss Heat escapes to the air; use an insulated cup, a lid and stir gently.
Measuring volumes
- Measuring volumes Use a burette or pipette in place of a measuring cylinder for better precision.
Starting temperature
- Starting temperature Make sure both solutions are at the same starting temperature.
Repeats
- Repeats Take repeats and calculate a mean to spot anomalies.
Part 5 of 5Safety
1Eye protection
- Eye protection Wear goggles throughout.
2Corrosive alkali
- Corrosive alkali 2 mol/dm3 sodium hydroxide can burn skin; wash splashes immediately.
3Acid
- Acid Hydrochloric acid is an irritant.
4Stable cup
- Stable cup Keep the cup in a beaker so it does not tip.
Key terms
| Term | Meaning |
|---|---|
| Calorimeter | An insulated container used to measure energy changes in a reaction. |
| Exothermic | Releasing energy to the surroundings. |
| Neutralisation point | The volume of alkali that exactly reacts with the acid. |
| Anomaly | A result that does not fit the pattern of the other data. |
| Mean | The average of repeated measurements. |
Avoid these mistakes
1
Using the first temperature reading instead of the maximum.
2
Joining the points with a single curve instead of two straight lines to find the peak.
3
Using a metal beaker as the only container, which loses heat quickly.
4
Not stirring, which gives uneven temperature readings.
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