Properties of Covalent, Ionic and Metallic Substances

This experiment compares the physical properties of covalent, ionic, and metallic substances by observing their appearance, luster, solubility in water, melting point, and electrical conductivity. By analyzing differences, students can infer the type of bonding present in each substance.

1. Gather small samples of each type of substance:
   • Ionic*: table salt (sodium chloride)
   • Covalent*: table sugar (sucrose) or paraffin wax
   • Metallic*: aluminum foil or copper wire
2. Observe the appearance and luster of each sample. Record whether the sample is shiny, dull, crystalline, or powdery.
3. Test solubility in water:
   1. Add a small amount (about 1 g) of each substance to separate test tubes containing 10 mL of distilled water.
   2. Stir each mixture and record whether the substance dissolves completely, partially, or not at all.
4. Test melting point (qualitatively):
   1. Place a small pinch of each substance on separate squares of aluminum foil.
   2. Gently heat each with a Bunsen burner or candle flame for up to 5 seconds.
   3. Record whether the sample melts, softens, or remains solid.
5. Test electrical conductivity:
   1. For solid conductivity: use a conductivity meter or circuit tester on each dry sample.
   2. For aqueous conductivity: test each water solution using the conductivity meter.
   3. Record if each sample conducts electricity in solid or aqueous state.
6. Summarize observations and classify each sample as ionic, covalent, or metallic based on its properties.

• None available

• Test additional materials such as graphite (covalent network) or brass (metallic alloy).
• Measure actual melting points using a hot plate and thermometer.
• Use different solvents (e.g., ethanol or oil) to test solubility differences.
• Compare the strength and malleability of metallic vs ionic crystals by gentle tapping.

• Wear safety goggles and gloves at all times.
• Keep flammable materials away from open flames.
• Do not touch hot metal or foil; allow samples to cool before handling.
• Do not taste or ingest any materials.
• Dispose of chemical waste properly and wash hands after the experiment.

• Which substance was shiny and conducted electricity? (The metallic sample.)
• Which substance dissolved in water and conducted when in solution? (The ionic compound.)
• Which substance melted easily and did not conduct electricity? (The covalent compound.)
• How do these observations relate to the type of bonding in each substance?
• Why do metallic substances conduct in both solid and molten states, while ionic substances only conduct when molten or dissolved?
• How does bond type affect melting point and solubility?