Changes of state and energy transfer
You're viewing free preview questions — 4 questions previewing here — subscribe to unlock 78 more, plus the Full Question Bank, Mock Papers & Worksheets.Upgrade

Changes of state and energy transfer — Free MYP5 Chemistry Practice Questions

1QuestionConstant temperature during phase changesConcept Practice
2 marks~3 minCriterion A
The heating curve for water shows two flat regions — one at 0∘C0^\circ\text{C} and one at 100∘C100^\circ\text{C}.
a
State what the term "latent heat of fusion" refers to in the context of the flat region at 0∘C0^\circ\text{C}. [1]
b
Explain why the kinetic energy of water molecules remains constant during the flat region at 0∘C0^\circ\text{C}, even though energy is continuously being supplied. [1]
Question diagram

Solutions

2QuestionMelting, freezing, boiling, condensation, sublimationAssessment Practice
5 marks~8 minCriterion C
A student heats a pure solid substance from room temperature to above its boiling point, recording temperature every 30 seconds. The substance melts at 80∘C80^\circ\text{C} and boils at 200∘C200^\circ\text{C}.

Temperature data collected:
- 00 to 120120 s: temperature rises from 20∘C20^\circ\text{C} to 80∘C80^\circ\text{C} (solid phase)
- 120120 to 240240 s: temperature remains at 80∘C80^\circ\text{C}, except at 180180 s where 82∘C82^\circ\text{C} is recorded
- 240240 to 360360 s: temperature rises from 80∘C80^\circ\text{C} to 200∘C200^\circ\text{C} (liquid phase)
- 360360 to 480480 s: temperature remains at 200∘C200^\circ\text{C} (boiling plateau)
- After 480480 s: temperature rises (gas phase)
a
Identify the anomalous reading and state why it is inconsistent with the data collected during the melting plateau. [2]
b
Explain, in terms of particles and energy transfer, why temperature remains constant throughout the melting plateau. [2]
c
The boiling plateau also shows a constant temperature. Evaluate whether the energy transfer occurring at the boiling plateau is the same as, or different from, that occurring at the melting plateau, and justify your reasoning. [1]
Question diagram

Solutions

3QuestionConstant temperature during phase changesAssessment Practice
6 marks~9 minCriterion D
A factory uses acetone (boiling point 56 °C) to clean metal parts. During a summer heatwave, the storage shed reaches 55 °C. The acetone remains liquid despite being only 1 °C below its boiling point.
a
Explain why the acetone does not boil at 55 °C. In your answer, refer to vapour pressure and the energy required for the phase change. [2]
b
A temperature spike raises the shed to 70 °C, causing rapid vaporisation of the acetone. Discuss the health risks to workers and one environmental consequence of this event. [3]
c
Evaluate one assumption made in part (b) and assess how relaxing that assumption changes the severity of the risk. [1]
Question diagram

Solutions

4QuestionEnergy transfer during state changes (heating/cooling curves)Assessment Practice
5 marks~8 minCriterion B
A group of students heats separate 10 g samples of stearic acid from 20∘C20^\circ\text{C} to 80∘C80^\circ\text{C} at three different rates, recording temperature every 30 seconds.

Heating rate (∘C min−1^\circ\text{C min}^{-1})0.51.02.0
Plateau duration (min)8.04.02.0
a
Deduce the relationship between heating rate and plateau duration. [1]
b
Justify a prediction for the plateau duration at a heating rate of 4.0∘C min−14.0^\circ\text{C min}^{-1}. [2]
c
Analyse how the fixed latent heat of fusion of stearic acid accounts for the plateau durations observed at different heating rates. [2]

Solutions

Questions 5-82

Unlock these questions with Premium

Sign Up →

That's every free question here — 4 of 82.

+78 more questions, plus Mock Papers & Worksheets, are waiting in Premium.

Upgrade