Core Practical: Investigating Changes of State (Edexcel IGCSE Physics)
Revision Note
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Core Practical 10: Investigating Changes of State
Aim of the Experiment
- The aim of this experiment is to investigate how the temperature of ice varies when it changes state from a solid to a liquid
Equipment List
- Resolution of measuring equipment:
- Thermometer = 0.1 °C
- Stopwatch = 0.1 s
Method
Apparatus used to heat ice and measure its temperature as it melts
- Place the ice cubes in the beaker (it should be about half full)
- Place the thermometer in the beaker
- Place the beaker on the tripod and gauze and slowly start to heat it using the bunsen burner
- As the beaker is heated, take regular temperature measurements (e.g. at one minute intervals)
- Continue this whilst the substance changes state (from solid to liquid)
- An example results table is shown below:
Analysis of Results
- Plot a graph of the temperature (y-axis) against time (x-axis)
- The graph will show regions where:
- The temperature of the ice cubes increases
- There is no temperature change (even though the ice cubes continue to be heated)
- This should occur at 0 °C, where the ice is melting from solid to liquid
A graph of temperature against time will show a flat region where the ice is melting
Evaluating the Experiment
Systematic Errors:
- Measurements of temperature from the thermometer keeping it at eye level, to avoid parallax errors
- Ensure the thermometer is held vertically in the beaker
Random Errors:
- Ensure there are enough ice cubes to surround the thermometer in the beaker, and only begin the experiment when the temperature is below 0 °C
- This is to ensure readings of temperature are as accurate as possible
Safety Considerations
- Wear goggles while heating water
- Place the bunsen burner, with the beaker and tripod, on a heatproof mat to avoid surface damage
- Make sure to stand up during the whole experiment, to react quickly to any spills
Exam Tip
You might be pleasantly surprised that heat can be transferred to a substance without changing its temperature. This is a very cool effect during changes of state: the thermal energy supplied does not contribute to the average kinetic energy of the particles in the ice - rather, it is used to weaken the bonds between the particles so they become freer to slide around each other (i.e. a liquid!)Once the ice is fully melted, the temperature of the liquid water begins rising again. Make sure you are familiar with the graph of temperature against time and you can associate the flat region with changing state
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