Chemistry- Experimental chemistry

• In experimental chemistry, the chapter can be split into two videos:

  • The first video covers physical quantities, apparatus, gas collection
  • The second video focuses on separation techniques, purification techniques, analysis for substance purity, and the importance of substance purity
• Key physical quantities in chemistry include time, temperature (melting point and boiling point), length, mass, and volume
• Units for physical quantities are used for communication and accuracy
• Common apparatus used:

  • Stopwatch, thermometer, temperature sensor (Data Logger) for temperature
  • Meter rule, measuring tape for length
  • Electronic balance for mass
• Mass vs. weight:

  • Mass is the amount of matter in a substance (kg, g)
  • Weight refers to the force due to gravity (Newtons)
• Measuring volumes of liquids:

  • Apparatus: pipette, volumetric flasks, measuring cylinders, buret
  • Measuring cylinders measure to the nearest 0.5, buret can measure to the nearest 0.05 cm³
• Techniques for gas collection:

  • Gas syringe is used to collect and measure small volumes of gas
  • Consider gas solubility in water and density compared to air for gas collection
• Methods for gas collection:

  • Displacement of water for insoluble or slightly soluble gases
  • Displacement of air for gases where water is not suitable
  • Upward delivery for gases less dense than air, downward delivery for denser gases
• Separation techniques and analysis methods are crucial in chemistry
• Methods involve verbs and a series of instructions
• Suitable separation and purification methods are chosen based on physical properties like solubility, melting point, and boiling point
• Interpreting paper chromatograms is important for analysis
• Different types of mixtures exist, such as solid-solid, solid-liquid, and liquid-liquid mixtures
• For solid-liquid mixtures, terms like solute and solvent are important to understand
• Magnetic attraction is used for solid-solid mixtures with magnetic properties like iron, cobalt, and nickel
• Sieving is used for solid-solid mixtures to separate substances based on particle size
• Filtration is used for insoluble solids in liquids
• Filtrate is the solution obtained after passing the mixture through the filter paper
• Evaporation to dryness separates dissolved solids from solvents by boiling off the solvent
• Crystallization is a method to obtain pure solids by allowing crystals to form from a saturated solution
• Crystallization is a gentler method compared to evaporation to dryness
• Crystals are washed with cold distilled water and dried between filter papers in crystallization
• Solubility curves help in understanding crystallization processes
• For liquid mixtures, there are miscible and immiscible liquids
• Miscible liquids dissolve in each other, forming a uniform solution
• Immiscible liquids have different densities and do not dissolve in each other
• Oil and water are an example of immiscible liquids where oil floats on water
• In single-celled organisms, substances can easily enter the cell due to a short distance, while in multicellular organisms, the distance is larger because of a higher surface area to volume ratio
• Multicellular organisms require specialised exchange surfaces for efficient gas exchange of carbon dioxide and oxygen due to their higher surface area to volume ratio
• For missable liquids, fractional distillation is used
• In simple distillation, solutes are present in a liquid, but the focus is on obtaining the solvent
• Boiling the mixture in a distillation flask and adding boiling chips for smooth boiling are steps in the distillation process
• Condensation takes place inside the condenser during distillation
• The purpose of a condenser is to provide a cool surface for vapors to condense into a liquid
• Cold water running in the condenser creates a temperature gradient for efficient condensation
• Fractional distillation is used when liquids have different boiling points, requiring a fractionating column to provide a large surface area for vapors to condense on
• The distillate is the product obtained through fractional distillation
• Fractional distillation separates liquids with different boiling points, like ethanol and water, by condensing them at different points along the fractionating column
• The energy absorbed during heating curves of substances like ethanol and water is used to overcome strong forces of attraction between particles
• Chromatography is used for analysis, not separation, and relies on substances having different solubilities in a given solvent