Change Of State
Overview
Heat a block of ice steadily and something remarkable happens: the temperature rises, pauses, rises again, pauses once more, then climbs a third time. Those pauses mark the moments when the substance is changing state, and understanding why the thermometer stalls is the key to unlocking this entire topic.
This lesson takes you through the particle model of solids, liquids and gases, explains every change of state, introduces specific heat capacity and the equation that links energy to temperature change, and shows you how to read and interpret heating curves. These ideas appear regularly across both Edexcel Papers 1 and 2.
Objectives
- Explain why heating a system will change the energy stored within the system and raise its temperature or produce changes of state
- Describe the changes that occur when a solid melts to form a liquid, and when a liquid evaporates or boils to form a gas
- Describe the arrangement and motion of particles in solids, liquids and gases
- Obtain a temperature-time graph to show the constant temperature during a change of state
- Know that specific heat capacity is the energy required to change the temperature of an object by one degree Celsius per kilogram of mass
- Use the equation: change in thermal energy = mass x specific heat capacity x change in temperature
- Investigate the specific heat capacity of materials including water and some solids
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Change Of State. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Which statement correctly describes the particles in a liquid? A) They vibrate about fixed positions B) They are far apart and move randomly C) They are close together and can slide past each other D) They are arranged in a regular pattern Answer: C
- During boiling, the temperature of a pure substance: A) Increases steadily B) Decreases steadily C) Stays constant D) Fluctuates up and down Answer: C
- What is the specific heat capacity of a substance? A) The energy needed to melt 1 kg of the substance B) The energy needed to raise 1 kg by 1 degree Celsius C) The temperature at which the substance changes state D) The energy stored in the bonds of the substance Answer: B
- A flat section on a heating curve indicates that: A) The heater has been switched off B) The substance has reached its maximum temperature C) A change of state is occurring D) The substance is cooling down Answer: C
- Which process is the reverse of melting? A) Boiling B) Evaporation C) Condensation D) Freezing Answer: D
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
Practice Mock Questions
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