Classifying and Separating Materials

Chapter 19 & 20: Classifying Materials and Separating Mixtures

Matter

  • Definition: Anything that takes up space and has mass.
  • States of Matter:
    • Solid
    • Liquid
    • Gas

Key Terms

  • Atoms: The building blocks of matter.
  • Molecules: Atoms that have joined together.
  • Particles: Refers to both atoms and molecules.

Pure Substances

  • Made up of only one type of particle (atom or molecule).
  • Elements:
    • Pure substances that cannot be broken down into simpler substances by chemical means.
    • Made of only one type of atom.
    • Examples: Sulfur (S), Carbon (C), Helium (He), Oxygen (O_2)
    • Elements have symbols, some from English names (S for sulfur, C for carbon) and some from other languages like Latin (Ag for silver, from argentum).
  • Compounds:
    • Pure substances made from two or more different elements that are chemically combined.
    • Made of more than one type of atom.
    • Example: Water (H2O), Carbon Dioxide (CO2), Salt (NaCl)

Elements and the Periodic Table

  • The periodic table lists all known elements.

  • To identify if a substance is an element, check if it is on the periodic table.

  • Example: Water is not on the periodic table, therefore it is not an element but a compound.

    Hoffman Voltameter Experiment:

  • Apparatus: Hoffman voltameter, power pack (or battery), dilute sulfuric acid.

  • Method:

    1. Fill the voltameter with water.
    2. Fill test tubes with water and invert them over the electrodes.
    3. Add sulfuric acid to the water to help the electric current flow.
    4. Connect the leads and turn on the current.
    5. Observe gas buildup in the test tubes.
    6. Stopper the test tubes under water.

  • Gases Produced:

    • Oxygen: Relights a glowing splint.
    • Hydrogen: Produces a squeaky pop with a lighted splint.

  • Water can be broken down into Hydrogen (H2) and Oxygen (O2) by chemical means.

Mixtures

  • Made up of two or more different particles mingled together.
  • Types of Mixtures:
    • *Homogeneous: Uniform composition throughout.
      *Heterogeneous: Non-uniform composition.
    • Soluble Mixtures: Substances that dissolve in a liquid.
      • Example: Sugar in water.
    • Insoluble Mixtures: Substances that do not dissolve in a liquid.
      • Example: Sand in water.

Solutions

  • Solute: A substance that dissolves in a liquid.

  • Solvent: A liquid that a substance dissolves in.

  • Solution: A mixture of a solute and a solvent.

  • Types of Solutions:

    • Dilute Solutions: Contain a little solute in a lot of solvent.
    • Concentrated Solutions: Contain a lot of solute in a little solvent.
    • Saturated Solutions: Solutions where no more solute will dissolve. Extra solute will fall to the bottom.

    Growing Crystals of Copper Sulphate Experiment:

  • Hypothesis: Crystals are formed from heating and cooling a saturated solution.

  • Method:

    1. Grind copper sulfate into a fine powder.
    2. Add copper sulfate to heated water and stir until a saturated solution is achieved.
    3. Place a sample into an evaporating dish and allow to cool.

  • Conclusion: Crystals can form from heating and cooling saturated solutions.

Physical vs. Chemical Changes

  • Physical Changes:

    • No new substance is made.
    • Examples: Crushing a can, sugar dissolving in water, smashing a glass, ice melting, mixing sand and water, chopping wood, water evaporating.

  • Chemical Changes:

    • A new substance is formed.
    • Examples: Iron and sulfur making iron sulfide, iron rusting, fireworks exploding, cooking an egg, methane gas burning in oxygen, wood burning, milk turning sour.

    Investigating a Chemical Change Experiment:

  • Reactants: Iron (Fe) and Sulfur (S)

  • Procedure:

    1. Mix iron filings and sulfur.
    2. Heat the mixture in a test tube.

  • Observation: A new substance, iron sulfide, is formed.

  • Conclusion: Chemical changes cause new substances to form.

Separating Mixtures

  • Filtration:

    • Separates an insoluble solid from a liquid.

    • The liquid passes through filter paper, leaving the solid behind.

      Separating an Insoluble Solid from a Liquid using Filtration Experiment:

  • Hypothesis: Insoluble solids can be separated from a liquid by filtration.

  • Conclusion: Filter paper can be used to separate an insoluble solid from a liquid because the pores on the filter paper are too small to allow sand particles to pass through.

  • Everyday Uses of Filtration:

    • Brewing coffee
    • Face masks
    • Kidneys filtering blood.

  • Chromatography:

    • A way of separating mixtures made up of many different parts.

      Separate the components of Black Ink using Paper Chromatography:

  • Hypothesis: Colors in an ink can be separated using chromatography.

  • Leaf chromatography separates leaf pigments according to their size.
    * Red - Anthocyanins
    * Orange - Carotenoids
    * Yellow - Xanthophyll
    * Green - Chlorophyll

  • Small molecules travel further than large ones.

  • Conclusion: Chromatography can separate soluble ink drops into its components.

  • Evaporation:

    • Separates a soluble solid from a liquid.

    • The liquid turns to gas, leaving the solid behind.

      Separate a Soluble Solid from a Liquid by Evaporation:

  • Hypothesis: Soluble solids can be separated from a liquid by evaporation.

  • Conclusion: The water escaped as gas (evaporates) and the salt remained in the dish.

  • Everyday Uses of Evaporation:

    • Drying clothes
    • Sweat drying
    • Salt from seawater.

  • Distillation:

    • Separates a soluble solid from a liquid.

    • The liquid turns to gas (evaporation), then condenses back into a liquid and is collected in a separate flask.

      Separate a Soluble Solid from a Liquid by Distillation:

  • Hypothesis: Soluble solids can be separated from a liquid by distillation.

  • Conclusion: Distillation allows for the separation of a soluble solid from a liquid and allows for both components of the mixture to be kept.

  • Uses of Distillation:

    • Alcohol Production.