Chemistry Methods and Techniques Quiz

Lab Equipment Advantages and Disadvantages

• Pipette:

  • Accurately measures liquid volumes to 25 cm³.
  • Measures a fixed volume.
  • Slow/solution slow to run out of pipette.

• Burette:

  • Accurately measures liquid volumes to 50 cm³.
  • More accurate than a measuring cylinder.
  • Slower than measuring cylinder.

• Measuring Cylinder:

  • Measures liquid volumes (25 cm³, 50 cm³, 100 cm³, and 250 cm³).
  • Easy to use/quick.
  • Not accurate.

• Conical Flask:

  • Holds and measures chemical liquid samples.
  • Easy to mix.
  • Chemicals can be heated, mixed, and boiled.
  • Difficulty in swirling/mixing/shaking (compared to a conical flask).

• Beaker:

  • Used for storing liquids, mixing, stirring, pouring, heating, and transporting liquids.
  • Holds and measures chemical liquid samples.

Other Lab Equipment

• Dropper (Teat pipette): Adds liquid in drops.
• Gas jar: For collecting gases.
• Trough: Holds liquid (water) for collecting pure gas samples over water.
• Wash bottle: To rinse lab glassware or salts to remove impurities.
• Mortar & pestle: Grinding/crushing solid substances into smaller pieces (powder).
• Crucible: Melting or heating solid chemicals over a burner at a very high temperature.
• Stand with clamp: Supports glassware at variable heights.
• Round bottomed flask: Heating and boiling liquids such as in distillation or other reagent reactions.
• Flat bottomed flask: Heating and boiling liquids in distillation or other reagent reactions. Not as durable as round bottom flasks and have sharp and vulnerable corners.
• Volumetric flask: Preparing a solution accurately to a specific volume.
• Gas syringe: Collects and measures the volume of a gas.
• Evaporating dish (basin): Heating a solution to allow evaporation of chemical solutions.
• Thermometer: Measuring temperature of solids, liquids, and gases.
• Watch glass: Usas as a lid for flasks or beakers used for evaporating solids or weighing samples.
• Top pan balance: Measuring mass of substances very accurately.
• Stopwatch: Measuring time taken.
• Stopper cork: Sealing openings of test tubes, flasks, and other lab glassware. Light and porous to prevent gas escaping.
• Bung: Sealing openings of test tubes, flasks, and other lab glassware. Made of rubber.
• Gauze: Helps spread heat off the flame evenly for heating.
• Tripod: Supports beakers for heating and boiling chemicals above a Bunsen burner.
• Bunsen burner: Produces flame for heating / warming a mixture.
• Funnel: Separating insoluble solid from a liquid with the help of a piece of filter paper.
• Separating funnel: Separating immiscible liquids of different densities.
• Stirring rod/glass rod: Stirring/mixing chemicals.
• Test tube: Used for storing, mixing, and heating small amounts of chemicals/liquids.
• Test tube holder: Holds test tubes while heating them.
• Test tube rack: Holds multiple test tubes upright at the same time.
• Condenser: Cools and condenses the vapour to be collected as a liquid.
• Thistle funnel Adds small volumes of liquids to an exact position.
• Metallic tongs: Holds hot crucibles, flasks, or beakers.
• Spatula: Transfers solid substances.
• Knife: Cutting soft metals (group 1).
• Spirit burner: Used for heating certain lab equipment/producing an open flame smaller than a Bunsen burner (often uses alcohol).
• Fractionating column: Separating liquid mixtures based on their boiling points.
• U-tube: Measuring pressure of liquids or cooling steam (water).
• Delivery tube: Gases travel one container to another.
• Boiling tube: Heating or boiling small quantities of liquid over a flame. Wide and thick.
• Filter tube: Passing gas through a liquid.
• Tap funnel: Separating immiscible liquids.
• Goggles: Protecting eyes from particles or hazardous materials.

Important Questions

• Explain one disadvantage of using a beaker instead of a conical flask.
  • Difficulty in swirling/mixing.
• Suggest and explain the effect on result when using burette instead of measuring cylinder
  • More accurate than measuring cylinder.
• What is used to transfer any solid in any experiment?
  • Spatula.
• What is the purpose of a watch glass?
  • Prevents splashing of liquids and decreases evaporation.

Important Notes (from the document)

• Thermometers are used to measure the temperature of liquid and gas.
  • Placed in the liquid.
  • NOT placed in gases
• Specific heat capacity can affect the temperature change when substances are heated or cooled.

Separation Techniques

• Filtration: Separates solids (soluble and insoluble) from liquids. Dissolve the mixture in excess to ensure complete dissolving, pour the mixture through a filter funnel and then the filtrate (soluble substance/liquids) will pass through the filter paper while residue (insoluble substance) will stay behind.
• Crystallization: Separating a soluble solid from water forming crystals. Half evaporate a solution, leave to cool, filter to get the crystals, dry between filter papers.
• Simple Distillation: Separates soluble solid from a liquid, e.g., mixture of water and sodium chloride. Boil the mixture, condense the vapor, and collect the liquid in a beaker. The remaining solid will be the insoluble solid.
• Fractional Distillation: Separates miscible liquids with different boiling points, such as ethanol and water.
• Separating Funnels: Separates immiscible liquids with different densities.

Electrolysis

• Electrolysis: Breaking down ionic compounds in molten or aqueous solutions using electricity.
  • In concentrated solutions: Less reactive ions discharged at the cathode & less complex ions discharged at the anode.
  • In dilute solutions: Water is electrolysed, H+ and OH- discharged.

Observations of Electrolysis

• If bulb is in the circuit, it will light.
• If gas is produced: Bubbles/ fizz/ effervescence. Colour of gas will be seen.
• If metal is formed: Color of metal (solid) will appear.

Electroplating

• Using electroplating, a small metal key can be coated with silver.

Acids and Bases

• Acid: Substance dissolving in water to produce hydrogen ions (proton donor). Contains excess H+ ions. Turns litmus red; has pH <7.
• Base: Substance dissolving in water to produce hydroxide ions (proton acceptor). Contains excess OH- ions. Turns litmus blue; has pH >7.

Reactions of Metals

• Reactions with acids: More reactive metals + acid → Salt + Hydrogen.
• Reactions with water: Most reactive metals + cold water → Metal hydroxide + Hydrogen. Mg reacts faster with steam producing Magnesium Oxide and Hydrogen.

Colors of Elements

• Metals such as silver, gold, and copper have characteristic colors.
• Non-metals display a wide range of colors in solid, liquid, and gaseous states.

Colors of Compounds

• Some compounds are colorless while others are brightly colored.
• Specific compounds associated with specific colors.

Test For Anions and Cations

• Test for specific anions (e.g., carbonate, chloride, bromide) and cations (e.g., aluminum, ammonium, calcium) through reactions with specific reagents.
• Results vary in color precipitate formation or gas evolution

Practical Investigation

• General guidelines for practical preparation and investigation methods.

Sources of Error

• Common sources of errors in experiments, their possible effects on results, and appropriate remedies or controls.

Other Practical Procedures

• Information on additional laboratory procedures and techniques are detailed in the provided text. This includes specific procedures for various types of investigations.