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Mixtures, Solutions & Chemical Processes

All matter can be broken down into two categories viz. pure substances and mixtures

  • A pure substance is any matter that always has the same composition or “make up”.
  • There are 2 classifications of pure substances: elements and compounds.
  • An element is a substance that cannot be broken down into simpler substances. An element is made up of only one type of atom.
  • A compound is a substance that is made up of 2 or simpler substances.

Mixtures Compounds

 

  • A mixture is a combination of 2 or more substances “non-chemically”.
  • This means we can separate a mixture without undergoing a chemical reaction or chemical change.
  • All mixtures can be classified into 2 groups: homogeneous and heterogeneous.
  • Homogeneous Mixture (Solvent + Solute) not distinguished. for ex. solution & colloids
  • Heterogeneous Mixture (Solvent + Solute) readily distinguished. for ex. suspension mixture

 

Separation Methods of Mixtures

For 2 Solids 

  • Suitable solvent
  • Sublimation
  • Magnet Use
For 2 Liquids 

  • Fractional Distillation (For miscible liquids)
  • Separating Funnel (For immiscible liquids) 
For Solids & Liquids

 

  • Filtration
  • Centrifugation
  • Evaporation
  • Crystallization  (Slow Cooling)
  • Distillation
  • Chromatography  (For different solubility solutes, esp. used in forensic science)

 

Difference between Mixture & Compound

Mixture Compound
  • Can be separated by physical methods (Filtration, Distillation)
  • Exhibit properties of its constituents
  • No energy change takes place
  • Variable composition
  • Can be separated by chemical methods
  • Exhibit different properties of its constituents
  • Fixed Composition
  • Energy change takes place

 


Solution, Suspension & Colloids

Solution

  • Homogeneous mixture with particle size < 1 nm diameter
  • Does not separate out on keeping still & cannot be separated by filtration
  • Does not scatter light due to extremely small particles
  • Examples include: Carbonated drinks, Salt & Sugar solution

 

Suspension  Solution Colloid

Colloids

  • Heterogeneous but appears homogeneous with particle size b/w 1 – 100 nm in diameter
  • Does not separate out on keeping still
  • Separates out on centrifugation, not by filtration
  • Scatters a beam of light – Tyndall Effect
  • include Milk, Blood, Soap solution, Ink, Jelly, Starch solutions, Body lotions, Foam, Gels, Gemstones etc.

 

Suspension

  • Heterogeneous mixture with particle size > 100 nm in diameter
  • Particles settle down on keeping still & separates out by filtration
  • Scatters a beam of light with particles of the solute seen easily.
  • Examples include: Sand in water, Milk of magnesia, Chalk solution in water

 

Solubility

  • Maximum quantity of solute in 100 gm of solvent at a particular temperature
  • Increases on increasing the temperature in liquids ( Decreases in case of gas)
  • No effect of pressure in liquids (solubility increases in case of gases on increasing pressure) 
  • Saturated Solution → No more solute can be dissolved without increasing temperature
  • Unsaturated Solution → More solute can be dissolved without increasing temperature

 


Important Chemical Processes

Diffusion

  • Spreading & mixing of one substance with the another due to the motion of particles, which continues till a uniform mixture is formed
  • Mixing particles move in zigzag known as Brownian motion
  • Increases with temperature, fastest in gases & slowest in solids
  • Few of the examples are : Dust particles in air, Smell of perfume in air, Spread of virus on sneezing, CO2 & O2 in water, Leakage of LPG (Identified by ethyl merceptane – a strong smelling substance)

 

Osmosis

  • Diffusion is the case of using semi permeable membrane b/w 2 mixtures
  • Only solvent is allowed to pass, from higher solvent conc. to the lower

 

Few of the examples are:

  • Preserving of pickle in salt
  • Swelling up of raisins in water
  • Earthworm dying when come in contact with salt

 

Dialysis

  • Same as osmosis but for transplantation of kidney in humans
  • Passes solvent & blocks waste

 

Latent Heat

  • To change the state of a substance from one to heat energy is required.
  • Latent heat does not increase temp. of a substance but is used in overcoming force of attraction b/w particle of a substance

It’s due to loss of latent heat that ice at 0*C is more effective in cooling than water at 0*C & due to gain of latent heat that steam at 100*C causes more severe burns than water at 100*C

 

Evaporation

  • Transition of liquid to vapour at normal temperature
  • Causes cooling when liquid evaporate as it draws latent heat of vaporisation from the liquid
  • For ex. evaporation of ether or spirit from our hand, sweating, water kept in earthen pot
  • Increases with temp, large surface area, wind speed & low humidity

 

Sublimation

  • Transition of solids directly into gases without going through liquid state
  • Ex: Dry ice, Camphor, Ammonium chloride, Iodine, Naphthalene, Anthracene
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