3.1 - Separating Techniques

Question 1

How do you conduct an investigation with chromatography?

Answer 1

1. draw a pencil line near bottom of paper
2. put dots of dye of same size on line spaced out evenly - let dry
3. place paper in a beaker with a small amount of solvent - BELOW PENCIL LINE
4. put a lid on the beaker - stop evaporation of solvent from paper’s surface
5. remove paper once solvent is about 1cm from top - solvent front
6. leave paper to dry so solvent evaporates

Question 2

What does it mean if an Rf value is big?

Answer 2

dye is very soluble in solvent

Question 3

What can fractional distillation be used to separate?

Answer 3

mixture of liquids - e.g. ethanol and water

Question 4

How does fractional distillation work?

Answer 4

separates liquids by taking advantage of their different boiling points

Question 5

What can simple distillation be used to separate?

Answer 5

components of a solution - e.g. sodium chloride solution

Question 6

What can crystallisation be used to separate?

Answer 6

solute from a solvent

Question 7

What can filtration be used to separate?

Answer 7

solid from a liquid

Question 8

How can we tell if a substance is pure?

Answer 8

melts + boils at fixed temps

Question 9

How can we tell if a substance is a mixture?

Answer 9

melts or boils over a RANGE of temps