Chemical Bonds, Toxic Substances, and Laboratory Methods

Posted on Mar 8, 2026 in Chemistry

Chemical Bonding and Matter

Ionic Bonds

  • Formed between metals and nonmetals.
  • Electrons are transferred from one atom to another.
  • Result: Positive and negative ions held by electrostatic attraction.

Covalent Bonds

  • Formed between nonmetals.
  • Electrons are shared between atoms.
  • Creates molecules with specific shapes.

Compounds

  • Two or more elements chemically bonded.
  • Properties differ from component elements.
  • Represented by chemical formulas.

Mixtures

  • Combination of two or more substances.
  • No chemical bonding; components retain their properties.

Solutions

  • Homogeneous mixture of solute and solvent.
  • Particles are evenly distributed and cannot be separated by filtration.

Changes in Matter

Physical Changes

  • No new substance is formed.
  • Change in state, shape, or size; often reversible.

Chemical Changes

  • New substances are formed.
  • Change in chemical composition.
  • Indicators: Color change, gas production, precipitate formation.

Balancing Chemical Equations

  • Law of Conservation of Mass: Atoms are neither created nor destroyed.
  • Adjust coefficients to balance atoms on both sides; do not change subscripts.

Toxic Plants and Animals

Toxic Plants

  • Poison Ivy (Toxicodendron radicans): Produces urushiol oil causing skin irritation. Remember: “Leaves of 3, let it be.”
  • Giant Hogweed (Heracleum mantegazzianum): Contains toxic sap causing severe burns; reacts with sunlight (photodermatitis).
  • Calabar Bean (Physostigma venenosum): Contains physostigmine; affects the nervous system.
  • Rhubarb (Rheum rhaponticum): Edible stalks, but leaves contain toxic oxalic acid.
  • American False Hellebore (Veratrum viride): Contains toxic alkaloids; often mistaken for edible plants.

Toxic Animals

  • Cane Toad (Rhinella marina): Secretes bufotoxins; dangerous to predators and pets.
  • Poison Dart Frog (Dendrobatidae): Skin contains potent batrachotoxins.
  • Portuguese Man o’ War (Physalia physalis): Siphonophore with venom-filled tentacles.
  • Lionfish (Pterois sp.): Venomous spines; invasive species disrupting reefs.
  • Fat-tailed Scorpion (Androctonus australis): Highly dangerous neurotoxic venom.

Environmental and Household Toxins

Heavy Metal Toxins

  • Copper: Essential trace element, but toxic in excess.
  • Lead: No safe exposure level; causes neurological damage.
  • Mercury: Bioaccumulates in fish; affects brain and kidney function.

Common Household Chemicals

  • Ammonia: Strong cleaner; dangerous if mixed with bleach.
  • Hydrogen Peroxide: Mild antiseptic; can irritate skin and eyes.
  • Rubbing Alcohol: Isopropyl alcohol; flammable and toxic if ingested.
  • Bleach: Sodium hypochlorite; reacts dangerously with acids.
  • Epsom Salts: Magnesium sulfate; safe in moderation, toxic in large doses.
  • Vinegar: Acetic acid; generally safe but can cause irritation.

Laboratory and Analytical Methods

Analysis and Separation

  • Chromatography: Separates mixture components based on solubility.
  • Separation of Mixtures: Physical methods like filtration, distillation, and evaporation.
  • Serial Dilutions: Stepwise reduction of concentration for toxicity testing.
  • pH Determination: Measures acidity (0) to alkalinity (14).
  • Conductivity Testing: Measures ion concentration and water purity.

Safety and Environmental Analysis

  • Effect of Dilution: Reduces toxin concentration and harmful effects.
  • Toxic Spills: Mapping spread via water, wind, or gravity for containment.

Nutritional Supplements

  • Calcium: Essential for bone health; excess can cause kidney stones.
  • Iron: Essential for blood production; high risk of poisoning in children.