Zadanie 2f
Wzorowane na: Chemistry HL Paper 1B, May 2026, TZ2, pytanie 2(f). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
Darmowe konto pozwoli wrócić do niego później.
Informacja do zadań 2a-2f.
Specific energy is the heat energy released per unit mass of fuel burnt. A student determined the specific energy of ethanol by burning it in a spirit burner under a copper can containing 120.0 g of water. The diagram shows the apparatus used.
The burner was weighed before and after each of five trials, and the temperature of the water was measured before and after heating. Fresh water was used for every trial.
| Spirit burner with ethanol | Trial 1 | Trial 2 | Trial 3 | Trial 4 | Trial 5 |
|---|---|---|---|---|---|
| Initial mass / g (± 0.001 g) | 148.236 | 147.801 | 148.115 | 147.652 | 148.021 |
| Final mass / g (± 0.001 g) | 147.374 | 146.870 | 147.370 | 146.774 | 147.121 |
| Water in copper can | Trial 1 | Trial 2 | Trial 3 | Trial 4 | Trial 5 |
|---|---|---|---|---|---|
| Initial temperature / °C (± 0.05 °C) | 20.4 | 19.8 | 22.0 | 21.2 | 21.3 |
| Final temperature / °C (± 0.05 °C) | 34.0 | 35.3 | 29.0 | 34.7 | 35.8 |
Polecenie
Suggest two ways in which the error in this experiment could be reduced.
Sprawdź rozwiązanieUkryj rozwiązanieKlucz CKE i punktacja
Odpowiedź z klucza
Any two of:
place a draught shield/insulation around the can «to reduce heat loss to the surroundings» ✔
put a lid on the can ✔
stir the water and record the highest temperature reached ✔
clamp the can so that the flame is a small, fixed distance below its base ✔
weigh the burner with its cap on, to prevent loss of ethanol by evaporation ✔
allow for the heat capacity of the copper can in the calculation ✔
use a larger mass of ethanol and a larger temperature rise ✔
Schemat punktowania
[2 max], list principle: two different, correctly described improvements that reduce heat loss or the error in the mass or the temperature. 'Repeat the experiment' does not reduce a systematic error and does not score.