2_Chem0

• Meniscus


  The curved upper surface of a liquid in a container
• Pycnometer


  • Used to measure the density of liquids
• Common errors done in measuring liquids
• Lower meniscus


  Read for clear or colorless liquids
• Upper meniscus


  Read for colored or not clear liquids
• Calibration of apparatus


  Marking the scale on the apparatus to allow measurement
• Taring


  Zeroing the balance to cancel out the weight of the container
• Analytical balance


  • Best used to measure small amounts of solid substances
• Common errors done in weighing substances
• Transferring liquids


  Pouring liquid from one container to another
• Pipette/dropper


  • Best used to transfer small amounts of acidic and basic substances
• How to prevent contamination when transferring liquids
• How to transfer odorous liquid substances
• Precautions when heating liquids in test tube

  • Wear safety goggles, gloves, and shoes
  • Point the test tube mouth away from yourself and others
  • Use the hottest part of the flame
  • Move the test tube from side to side
• Direct heating


  Heating the test tube from the bottom
• Indirect heating


  Heating the test tube at the top or at an angle
• Why the test tube was held at a 45 degree angle
• Precipitation


  The process of creating a solid in a solution during a chemical reaction
• Precipitate


  The solid form created in a precipitation reaction
• Purpose of precipitation


  Favorable method of product isolation in chemistry
• Principles of filtration


  • Removes solid particles from a liquid or gas
  • Can recover both the filtrate and the solid filter cake
• When is filtration used in the laboratory
• Residue


  The solid material left behind on the filter paper
• Filtrate


  The liquid that passes through the filter paper
• Decantation


  The process of pouring away a liquid while leaving a solid behind
• Supernatant liquid


  The liquid layer above a precipitate
• Difference between sedimentation and decantation
• Evaporation


  The process of converting a liquid into a gas
• Filtration


  After the filtrate has been collected, pass a small amount of the wash liquid through the filter paper to wash the residue
• Filtration


  The process of separating a solid from a liquid by passing the mixture through a porous medium that retains the solid and allows the liquid to pass through
• Residue


  The solid material that remains on the filter paper after filtration
• Filtrate


  The liquid that passes through the filter paper during filtration
• Decantation


  Pouring away a liquid while leaving a solid (often a precipitate) behind
• Decantation is the process of pouring away a liquid while leaving a solid (often a precipitate) behind
• Apparatuses used in decantation

  • Glass rod
  • Receiving container
• Decantation basic steps and tips

  1. Put a stirring rod on the mouth of the container to avoid trickling of the liquid to the outside

  2. Tilt the container and slowly decant the supernatant

  3. Pour suitable washing solvent to the precipitate and transfer the solvent by decantation. Repeat a few times to wash the precipitate
• Supernatant liquid


  The liquid layer above a solid precipitate after settling or centrifugation
• Sedimentation


  The process of allowing particles to settle out of a liquid by gravity
• Decantation


  The process of pouring off the liquid from a container while leaving the solid residue behind
• Evaporation


  The process in which the solvent of a solution is converted into a vapour to leave a solid or liquid solute