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Year 7 Science-Chromatography

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Lucia Scherrer

on 16 August 2016

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Transcript of Year 7 Science-Chromatography

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What happens when you get your paper wet?

It doesn't always smudge and blur, as you might expect. Sometimes it splits up into weird coloured streaks that creep across the page.

We can also use it by design to split up mixtures and other substances into their components.

Chromatography is actually one of the most useful analytical techniques chemists have at their disposal, helpful in everything from identifying biological materials to finding clues at crime scenes
What is chromatography?

Chromatography means "colour writing" (from the Greek words chroma and graphe).

Chromatography is a way of separating out a mixture of chemicals (gas or liquid)


We have a liquid (the food colouring) dissolved in water (solvent) absorbed over the surface of a solid (the paper).
Mobile phase and stationary phase

The moving substance is called the
mobile
phase and the substance that stays put is the
stationary
phase.

As the mobile phase moves, it separates out into its components on the stationary phase (filter paper).
What is chromatography used for?

Year 7 Science-Chromatography

How does chromatography work?
Think of chromatography as a race.

Waiting on the starting line you have a bunch of runners.

When a race starts, runners soon spread out because they have different abilities.

In exactly the same way, chemicals spread out because they travel at different speeds over a stationary solid.

Chromatography
works because different colours have different
solubilities

forensic science
(crime scenes)

in pollution monitoring
(for identifying small concentrations of unknown pollutants in air and water samples)


fo
r studying complex mixtures
in such things as food, perfume, petrochemical, and pharmaceutical production.
Terminology:

solute-
a substance that is dissolved in a solvent to form a solution

solubility
- how quickly it dissolves

solvent
-a substance in which a solute dissolves to form a solution

soluble
- able to be dissolved


Practical experiment
:
To separate mixtures (ink from pens) into their parts by allowing the mixture to be adsorbed by a solid (filter paper)


Record your experiment
Title:

Aim:
Method:
Results/Observation:
Equipment:
Aim:
Equipment:
Method:
Conclusion:
Collect your equipment from the front:

1x Beaker

1 x watch glass

2 x strips of filter paper already in the beaker

1x round piece of filter paper

paper clip

ruler

pencil

two different coloured pens
1. Draw a pencil line 2 cm up from the bottom of
your filter paper- this is the start line for your marker pens.

2. Choose 2 different coloured pens.

3. Wet them and place the colour along the pencil line.

4. Fill beaker with 1 cm of water.

5. Place filter paper so it's
just
touching the water.

6. Watch the colours and record your observations.
As the water creeps up the absorbent paper, it carries the color with it. Some components of the ink travel farther than others, causing the different colors to spread out so you can see them.
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