4.2.3Solids, Liquids and Gases: Part 1
Core Practical: Investigating Changes of State
5 min read 4 parts Lesson 7 of 9 Unit quiz
Section 1 of 4Setting Up
Setting Up
Aim
- To investigate how the temperature of ice varies with time as it is heated and melts.
Apparatus
- A 400 cm³ beaker half full of crushed ice, a thermometer, a tripod and gauze, a Bunsen burner and a stopwatch.
Variables
- The independent variable is time and the dependent variable is temperature;
- the mass of ice and the heating rate are controlled.
Resolution
- A thermometer reading to 0.1 °C and a stopwatch measuring to 0.1 s give sensible precision.
Section 2 of 4Method
1
Half fill the beaker with ice and place the thermometer in the middle, surrounded by ice.
2
Place the beaker on the tripod and gauze and heat it gently with the Bunsen burner on a low flame.
3
Stir gently and record the temperature every minute as the ice warms and melts.
4
Continue recording while the ice melts completely and, if time allows, until the water warms further.
5
Plot a graph of temperature on the y-axis against time on the x-axis.
Section 3 of 4Analysis and Evaluation
Rising section
- At the start the temperature rises below 0 °C, because energy increases the kinetic energy of the particles.
Flat section
- The graph is level at 0 °C while the ice melts, because the energy supplied breaks bonds and does not raise the temperature.
Final rise
- After all the ice has melted, the temperature of the water rises again as kinetic energy increases.
Reducing errors
- Read the thermometer at eye level to avoid parallax and keep it vertical, surrounded by ice but not touching the beaker.
Safety
- Wear goggles, stand up to react to spills, and use a heatproof mat under the Bunsen burner.
| Stage | Temperature | Reason |
|---|---|---|
| Ice below 0 °C warming | Rises | Kinetic energy increases |
| Ice melting | Constant at 0 °C | Energy breaks bonds |
| Water warming | Rises | Kinetic energy increases |
Section 4 of 4Exam Checklist & Tips
4.2.3 – Key Points for the Exam
- Melting point The temperature at which a solid changes to a liquid, 0 °C for pure ice.
- Parallax error An error caused by reading a scale from the wrong angle.
- Resolution The smallest change a measuring instrument can detect.
- Heating curve A graph of temperature against time as a substance is heated.
- Potential energy store The energy associated with the positions of particles relative to each other.
Common Mistakes
- Saying the temperature stays constant because no energy is being supplied;
- energy is still supplied but changes the bonds.
- Plotting temperature on the x-axis instead of the y-axis.
- Placing the thermometer against the beaker, which reads the glass temperature rather than the ice.
- Starting the timing after the ice has already begun to melt.