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Introduction

The physical properties of a substance include its density, its melting point, and its boiling point. All substances have a unique set of physical properties. You are to investigate the physical properties of some liquids, and then use the internet to identify an unknown substance by its physical properties.

Task 1: Investigating physical properties


A simulation to investigate the physical properties of compounds

  1. Open Yenka file Model 1.
  2. The beakers contain 50 cm3 of each liquid. Mercury, although a metal, is still a liquid as its melting point is lower than room temperature. Record the mass of the beaker on the balance. Now pour in the mercury and record the new mass. Calculate the mass of mercury.
    Mass of beaker + mercury =
    Answer
    720 g
    Mass of beaker =
    Answer
    40 g
    Mass of mercury =
    Answer
    680 g
  3. To find the density of a substance, its mass is divided by its volume. Calculate the density of mercury. Show your working and include units in your answer.
    Answer
    Density = 680 g / 50 cm3 = 13.6 g/cm3
  4. Place the mercury on the heater, select the beaker and look at its atom viewer. Use the slider (or the heater's properties) to increase the temperature to 445 °C. The temperature increase should be plotted on the graph. After a steady rise, the temperature should remain constant when the mercury boils. The energy supplied by the heater is used to overcome the forces between the mercury particles rather than speed up their motion and thus increase the temperature. At what temperature does the graph flatten out?
    Answer
    Around 356 °C
  5. Reload the simulation (by pressing F5) and carry out identical measurements for the sample of sulfuric acid. When heating this sample, only turn the heater up to 331 °C as it has a lower boiling point than mercury. Summarise your results in the table below. Include units and working.
    Mass of beaker + sulfuric acid =
    Answer
    94.9 g
    Mass of beaker =
    Answer
    40 g
    Mass of sulfuric acid =
    Answer
    94.9 − 40 = 54.9 g
    Density =
    Answer
    54.9/50 = 1.1 g/cm3
    Boiling point =
    Answer
    around 101 °C
  6. Reload the simulation and carry out identical measurements for the sample of ethanol. When heating this sample, only turn the heater up to 115 °C as it has a lower boiling point than sulfuric acid. Summarise your results in the table below. Include units and working.
    Mass of beaker + ethanol=
    Answer
    79.24 g
    Mass of beaker =
    Answer
    40 g
    Mass of ethanol =
    Answer
    79.24 − 40 = 39.24 g
    Density =
    Answer
    39.24/50 = .78 g/cm3
    Boiling point =
    Answer
    around 78 °C
  7. Reload the simulation and carry out identical measurements for the sample of water. When heating this sample, only turn the heater up to 115 °C again. Summarise your results in the table below. Include units and working.
    Mass of beaker + water=
    Answer
    90 g
    Mass of beaker =
    Answer
    40 g
    Mass of water =
    Answer
    90 − 40 = 50 g
    Density =
    Answer
    50/50 = 1 g/cm3
    Boiling point =
    Answer
    around 100 °C

Task 2: Identifying an unknown substance

  1. An unknown substance is found to have the physical properties listed below. Visit this website and use the information there to identify the unknown substance. Temperatures on this website are measured in Kelvin (0 K = −273 °C. 0 °C = 273 K).
    Density = 8.9 g/cm3
    Boiling point = 3193 K
    Melting point = 1726 K

    Write down the name of the substance.

    Answer
    Nickel.
  2. Give a use for this element. You may need to visit other websites.
    Answer
    E.g. in coins.

Summary

The unique set of physical properties of a substance allow us to identify an unknown substance from its measured physical properties.

Teacher Summary

  • For a related exercise on boiling points, see the activity Heating Curves.
  • Pupils will need access to the internet for the research section of this exercise.