• Fractional distillation is a separation technique used to separate miscible liquids that have different boiling points. It is most effective when separating components of a homogeneous liquid mixture.
• Ethane and octane are both hydrocarbons that mix completely and have sufficiently different boiling points to be separated by this technique.

\(\Rightarrow D\)

• Hexane and water are immiscible, so they do not mix and, instead, form separate layers.
• As a result, they can be separated effectively with a separating funnel. The density of hexane is lower than the density of water, so the hexane will be the upper layer and the water will be the lower layer.
• The liquids could also be separated effectively through distillation.
• They have a large difference in boiling points. Hexane has a lower boiling point than water (68.7°C). As such, it will be the first fraction to be collected during distillation.

• Oil and water are immiscible — they form two distinct layers due to different densities.
• A separating funnel allows the denser liquid (water) to be drained off first, leaving the oil layer behind.
• Filtration only separates solids from liquids.
• Chromatography separates substances based on solubility and adsorption, not density.
• Evaporation removes a solvent, not separate two immiscible liquids.

\(\Rightarrow C\)

a.    The mixture is a heterogeneous mixture.

• This is because the components retain their individual physical properties and can be seen as separate phases (solid particles with different appearances).
• They do not form a uniform composition.

b.    
       

• The flow chart should outline steps that can be completed in a school science lab.

a.   Separation technique:

• Evaporation is a suitable technique because water has a much lower boiling point than salt.
• By heating the solution, the water evaporates, leaving salt crystals behind.
• Further distillation could be used to collect and condense the evaporated water.

b.   Physical property:

• Iron fillings are magnetic and hence can be separated using a magnet.
• The mixture is heterogeneous.

c.   Safety precaution:

• For evaporation, wear heat-resistant gloves when handling hot equipment like the tripod or beaker to avoid burns to the hands.

• Magnetism can be used to separate iron filings from the mixture. Iron filings are magnetic, so you can easily separate them from the non-magnetic sand and salt by moving a magnet over the surface of the mixture.
• Filtration can be used to separate the sand from the salt. Add water to the remaining mixture of sand and salt, and stir well to dissolve the salt. Since sand is insoluble in water, you can separate it by pouring the mixture through a filter paper placed in a funnel.
• Evaporation can be used to recover the salt. Finally, to separate the salt from the water, heat the saltwater solution until the water evaporates. The salt will be left behind as a solid residue.

• Each of the components in the mixture have their own unique physical properties which can be exploited to separate them.

Mixture separation process:

1. A sieve can be used to separate the sand from the mixture.
2. Following this, a distillation set up can be used to remove the methanol from the mixture (as methanol has a lower boiling point than water).
3. An evaporating basin can then be used to evaporate the water, leaving salt behind.

\begin{array} {|l|c|}
\hline
\rule{0pt}{2.5ex} \text{Separation Method} \rule[-1ex]{0pt}{0pt} & \text{Physical Property Exploited} \\
\hline
\rule{0pt}{2.5ex} \text{Filtration:} \rule[-1ex]{0pt}{0pt} &  \text{Particle size} \\
\hline
\rule{0pt}{2.5ex} \text{Evaporation:} \rule[-1ex]{0pt}{0pt} & \text{State of matter} \\
\hline
\rule{0pt}{2.5ex} \text{Distillation:} \rule[-1ex]{0pt}{0pt} & \text{Boiling point} \\
\hline
\end{array}