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.

• 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 [arr] (Solvent + Solute) not distinguished. for ex. solution & colloids
• Heterogeneous Mixture [arr] (Solvent + Solute) readily distinguished. for ex. suspension mixture

Separation Methods of Mixtures

Difference between Mixture & Compound

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

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 [arr] No more solute can be dissolved without increasing temperature
• Unsaturated Solution [arr] 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