# Pearson’s Edexcel IGCSE Physics Change of State Specification focus questions and answers

## Questions

What factors determine the energy stored within a system and how it affects the temperature or changes of state?

How do the properties of a solid differ from those of a liquid and a gas when a solid melts?

Can you explain the arrangement and motion of particles in solids, liquids and gases?

What is the process of obtaining a temperature-time graph to show the constant temperature during a change of state?

What is specific heat capacity and how is it measured?

How can the equation change in thermal energy = mass × specific heat capacity × change in temperature be used to calculate the energy required to change the temperature of an object?

Can you provide an example of how to investigate the specific heat capacity of materials such as water and solids?

How does the specific heat capacity of a substance affect the amount of energy required to change its temperature?

How can the concept of specific heat capacity be applied in real-world situations?

How does the specific heat capacity of a substance relate to its ability to store thermal energy?

Heating a system will change the energy stored within the system and raise its temperature or produce changes of state due to the increase in kinetic energy of the particles within the system. This causes the particles to move faster and have a higher potential energy, leading to an increase in temperature or changes in the physical state of the substance.

When a solid melts to form a liquid, the particles of the solid lose their fixed positions and arrangement and gain more freedom of movement. The liquid formed has a lower density and a higher viscosity than the solid. When a liquid evaporates or boils to form a gas, the particles gain even more freedom of movement and the density of the substance decreases further.

In solids, the particles are closely packed and have a fixed position and arrangement. They vibrate about their fixed positions but do not move from one place to another. In liquids, the particles are more loosely packed than in solids and are free to move about but still maintain a fixed volume. In gases, the particles are far apart and move freely, filling the container they are in.

To obtain a temperature-time graph to show the constant temperature during a change of state, a thermometer is used to measure the temperature of the substance at regular intervals while it is undergoing a change of state. The temperature readings are then plotted against the corresponding time intervals to show the constant temperature during the change of state.

Specific heat capacity is the amount of energy required to change the temperature of a substance by one degree Celsius per unit mass. It is measured in units of J/kg°C. It can be measured by using the equation: change in thermal energy = mass x specific heat capacity x change in temperature (ΔQ = m x c x ΔT).

The equation change in thermal energy = mass × specific heat capacity × change in temperature can be used to calculate the energy required to change the temperature of an object by using the specific heat capacity of the substance and the mass and change in temperature of the object.

To investigate the specific heat capacity of materials such as water and solids, the substance can be heated using a known amount of energy and the change in temperature can be measured. The specific heat capacity can then be calculated using the equation ΔQ = m x c x ΔT.

The specific heat capacity of a substance determines the amount of energy required to change its temperature. A substance with a higher specific heat capacity requires more energy to change its temperature than a substance with a lower specific heat capacity.

Specific heat capacity can be applied in real-world situations such as in the design of heat exchangers, cooking, and energy storage.

The specific heat capacity of a substance relates to its ability to store thermal energy. A substance with a higher specific heat capacity can store more thermal energy than a substance with a lower specific heat capacity.