Separating Mixtures Two types of mixtures Homogeneous mixtures

Separating Mixtures

Two types of mixtures • Homogeneous mixtures – where everything looks the same but is made up of two or more types of pure substances – SOLUTIONS! – Milk, juice, salt and water • Heterogeneous mixtures – where we can spot the difference with our eyes between particles – Gravel, lego – We usually refer to them as mechanical mixtures

Hand Separation • Using our hands or tools that we use with hands • Sieve, magnets, or our hands • Separating by particle size

Filtration • Similar to sieve but for finer particles. • Usually for small particles formed in a solution – Precipitate

Evaporation • Between a solid and liquid • We evaporate the liquid and have the solid left behind • Think of sand water • Evaporate the water, get left with the sand • We use the boiling point of the liquid to evaporate it.

Distillation • Between a liquid and a liquid. • Similar to evaporation but between the boiling points of two liquids • Example – Water has a boiling point of 100°C – Methanol has a boiling point of 64°C – We can heat up the mixture to 70°C and let the methanol boil and leave the water behind.

Solvent Extraction • Using the information about solvents dissolving certain solids • Sugar and sand – Sugar dissolves in water – Sand does not dissolve in water – Pour water in, dissolve the sugar and collect the sand.

Solvent Extraction • • Same can be done to liquids and liquids Some liquids mix Some liquids do not mix “Like dissolves like” Polar dissolves polar Non-polar dissolves non-polar Do not worry about the last 2 points as much.

• Oil (non-polar) and water (polar) do not mix • We call them immiscible. When liquids do not mix • Two liquids that mix (methanol and ethanol) we say they are miscible • In order to separate, we let the liquids sit and the denser one will usually sink. We can use a funnel to remove.

Recrystallization • Similar to evaporation, but inside a solution. • Remember a solution is a HOMOGENEOUS MIXTURE! So we might not know there are solids inside. • We heat up the solution and allow the liquid to evaporate. The solid will recrystallize again • Water and salt

Gravity Separation • • • We let gravity separate it Density is involved Denser substances sink Less dense substances float We can speed this up using a centrifuge

Video

Chromatography • Chroma means colour in Greek • Separation using colour • Turn to page 57

Video!

Pg 58 Separation Table

Homework • Pg 58 • #45 -47 • #54 and 58