Identification unknown substances

Aim

The aim of this experiment is to classify some unknown substances as metallic, ionic or covalent using physical and chemical tests.

 

Introduction

You will be provided with 8 samples and you should devise a simple set of tests to identify the different substances. A suggested sample set includes: sugar, sodium chloride, sodium thiosulphate, gas jar of oxygen, distilled water, ethanol, magnesium powder and iron powder.

Requirements

  • safety glasses
  • 6 test-tubes in rack
  • 6 ignition tubes
  • test-tube holder
  • Bunsen burner and protective mat (note: the maximum temperature for most Bunsen Burners is 800°C)
  • beaker, 100 cm3
  • battery and lamp in holder
  • 2 carbon electrodes
  • 3 connecting leads with crocodile clips
  • unknown substances, in bottles labelled A-H

 

Results Table

  Sample A Sample B Sample C Sample D
Appearance        
Estimate of boiling-point        
Conductivity of solid        
Solubility in water        
Conductivity of solution        
Action of dilute HCl(aq)        
Structure        

 

  Sample E Sample F Sample G Sample H
Appearance        
Estimate of boiling-point        
Conductivity of solid        
Solubility in water        
Conductivity of solution        
Action of dilute HCl(aq)        
Structure        

 

Questions

  1. What further tests would probably help to identify the structures which you could not identify in the experiment?
  2. Why is it more difficult to recognise a powdered metal than a solid lump?