Understanding Elements, Mixtures, and Compounds

Definitions

• Element: A substance that cannot be broken down into anything simpler.
• Mixture: A combination of two or more substances mixed together in any proportion, not chemically bonded.
• Compound: A substance made from two or more elements chemically combined.

Examples

• Iron (Fe): A metal element, dark gray crystals.
• Sulfur (S): A non-metal element, bright yellow powder.

Experimental Tests

Four main tests are conducted to differentiate between iron, sulfur, and their mixtures/compounds:

1. Appearance
2. Action of Water
3. Action of Acid
4. Action of Magnet

Tests on Iron and Sulfur Separately

• Appearance:
  • Iron: Dark gray, sinks in water.
  • Sulfur: Bright yellow, floats in water.
• Action of Acid:
  • Iron reacts with acid, producing hydrogen gas (confirmed by a 'pop' sound test).
  • Sulfur shows no reaction with hydrochloric acid.
• Action of Magnet:
  • Iron is attracted to a magnet.
  • Sulfur is not attracted.

Tests on Mixture of Iron and Sulfur

• Iron and sulfur maintain their separate identities and behaviors:
  • Appearance: Separate dark gray (iron) and bright yellow (sulfur) components.
  • Action of Water: Iron sinks, sulfur floats.
  • Action of Acid: Iron reacts to produce hydrogen gas.
  • Action of Magnet: Iron is attracted, sulfur is not.

Tests on Heated Mixture of Iron and Sulfur

• On heating, iron and sulfur chemically bond to form Iron(II) Sulfide:
  • Appearance: Black solid, differing from iron or sulfur.
  • Action of Water: Compound sinks with no separation.
  • Action of Acid: Reacts to form toxic hydrogen sulfide gas.
  • Action of Magnet: Not attracted to a magnet (unless excess iron is present).

Conclusion

• Elements: Retain separate properties and identities.
• Mixtures: Components can be physically separated and retain their properties.
• Compounds: Form new substances with different properties through chemical bonding.