Measuring the temperature change of a reaction in an insulated cup, the variables, repeats and the two-line graph.
What you will learn
- Describe the method for measuring a temperature change
- Name the variables
- Find the maximum temperature rise from two lines of best fit
The method
- Measure 30 cm³ of acid into a polystyrene cup standing in a beaker (so it does not tip).
- Record the starting temperature.
- Add the alkali 5 cm³ at a time, stir, and record the highest temperature each time.
- Carry on past the point where the temperature starts to fall.
- Repeat and calculate means.
A lid and the polystyrene cut energy transfer to the room, so the measured rise is closer to the true one.
Repeats show how reliable a result is. The temperature rise is the highest temperature minus the starting temperature. The mean is the total of the repeats divided by how many there are; the range is the largest repeat minus the smallest; and the uncertainty in the mean is about half the range.
- rises 9.2, 9.6 and 9.4 °C
- mean = (9.2 + 9.6 + 9.4) ÷ 3 = 9.4 °C
- range = 9.6 − 9.2 = 0.4 °C, so uncertainty = ± 0.2 °C
The rest of this lesson and its 10 practice questions are locked.
In this lesson
- The method
- Two lines tell you the end point
- Try it: Find the crossing point
10 practice questions, marked as you go; about 20 minutes in all.
Key terms
Lid, Polystyrene, Mean, Range
In this unit: Energy changes
Exothermic and endothermic reactions, the temperature change practical, reaction profiles, bond energies, cells and fuel cells.
- Exothermic and endothermic reactions
- Required practical: temperature changes
- Reaction profiles
- Bond energies
- Chemical cells and fuel cells