FILTRATION AND CHROMATOGRAPHY

 

 

1. Objectives

To learn how to apply filtration to make lime water

To learn how to separate mixed colour pigments using paper chromatography

 

2. Materials and tools (per one group)

For filtration to make lime water: a test tube rack or improvised test tube stands, a 15cm diameter filter paper disc, an improvised beaker (Voltic bottle), an improvised funnel, a plastic beaker (or glass beaker), a glass rod, a test tube, plastic straws (or glass tubes), small amount of desiccant power (or Ca(OH)2, power), a filtered water bag

 

For separation of food colours: a paper strip (10mm x approximately 20cm), a test tube, a thin glass tube (or capillary tube), food colours mixture, a pin, a cork which fits to the test tube, methanol

 

For separation of fluorescent marker colours: a marker colour strip (if the lesson time is enough make students prepare the strip), a test tube, a pin, a cork, 70% ethanol

 

For separation of leaf colour pigments: a 11cm diameter filter paper disc, a Voltic bottle cap, a plastic Petri dish (glass is the best), a mortar, a pestle, a thin glass tube or a hematocrit capillary, a pair of scissors, 5ml nail polish remover (acetone), 10ml measuring cylinder, kerosene

 

3. Safety concerns

Confirm following to students

Do not breathe in nor drink methanol

Use chemicals only at the teacher’s lab table; do not move them to students’ lab table.

Do not make fire near chemicals (methanol, ethanol, acetone, kerosene are highly inflammable)

 

4. Activities

Filtration

1)        Collect used desiccant powder or calcium hydroxide powder (do not use new calcium oxide).

2)        Put small amount of powder in an improvised beaker.

3)        Add some filtered water in the beaker and stir with a glass rod.

4)        Make a filtration set up.

5)        Filter the liquid slowly.

6)        Put small amount of the filtrate into a test tube (about 1 cm deep).

7)        Pass your expiration through the filtrate gently using a plastic straw.

 

Chromatography

A. food colour mixture

1)        Put methanol in a test tube about 1cm from the bottom.

2)        Spot small amount of the mixture on a paper strip using the thin glass tube.  Spot approximately 2.5 to 3cm from the lower edge of the strip.

3)        Adjust the length of the strip to suit the length of the test tube.

4)        Suspend the strip in the test tube using a pin and a cork.  Soak the lower end of the strip in the solvent (methanol) but do not soak the spot in it).

5)        Observe the separation of the colours.

 

B. fluorescent marker colours

1)        Put 70% ethanol in a test tube about 1cm from the bottom.

2)        Absorb the colours of the marker in a paper strip in such a way that mark lines on the same place about 3cm apart from the lower end of the strip.

3)        The following procedures are as same as “food colour mixture chromatography”.

 

C. leaf colour pigments

1)        Using a pair of scissors remove rectangular strip from the filter paper disc like the drawing shown left.  Bend the remaining parts of the strip of the paper disc downward.

2)        Collect 10 small leaves (about 3cm long, thin and soft leaves from the same species of green plant).

3)        Grind the leaves with mortar and pestle adding 5ml acetone (nail polish remover).  Acetone extracts leaf colour pigments from the leaves.

4)        Using a thin glass tube or capillary suck small amount of the extract and make three small spots near the centre of the filter paper disc touching the tube on the filter paper.

5)        Make the spots dry about one minute then repeat spotting and drying at least four times.

6)        After the final spotting dry the spots at least five minutes.

7)        Put a plastic bottle cap at the centre of a 90mm diameter Petri dish.  Pour kerosene in the cap.

8)        Put the short strip of the paper disc in the kerosene and wait at least 20 minutes for the separation of the colour pigments.
If it is possible cover the set with bigger glass container to make inside of the container saturated by kerosene vapour.

 

5. Activity/assignment sheet

SEPARATION 2

 

Class:

 

Group:

 

Date:

 

 

Names of group member (fill in block letters)

Index number

First name

Middle name

Last name

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1. Describe the following chemical reactions with chemical equations

 

1)        Calcium oxide to calcium hydroxide (reaction between calcium oxide and water)

 

2)        Calcium hydroxide to calcium carbonate (reaction between calcium hydroxide and carbon dioxide)

 

3)        Calcium carbonate to calcium hydrogen carbonate (calcium carbonate and carbon dioxide and water)

 

4)        Calcium carbonate to calcium oxide (heat above 550°C)

 

2. Illustrate the result of chromatography using colour pencils

sample

Food colour

Fluorescent

marker

Leaf colour pigments

solvent

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3. Summarize in five points the important safety guidelines for basic school experiments

1)                                                                                         

2)                                                                                         

3)                                                                                         

4)                                                                                         

5)                                                                                         

 

 

inserted by FC2 system