Chromotography is a collective term for a set of laboratory techniques used to separate mixtures. It includes paper chromotography, thin-layer chromotography and gas chromotography. Paper chromotography is used for separating mixtures such as inks and dyes. In our practical experiment, we will use the natural food dyes used to colour “Smarties”, although the artificial colouring used for “M and M’s” work well too. This is also a great time of year to investigate the pigments in autumn leaves – as chlorophyll breaks down to produce xanthophyll, carotene and anthocyanin. Another experimental method for leaf chromotography here.
Why do some trees have leaves that change colour in the autumn? How is chromotography used by forensic scientists and in industry? Please do some research and post your answers in the comments section below.
This a rusty tractor engine, captured at Jurien Bay, WA.
Over the next few weeks we will be doing many different experiments, including turning grass into paper. After you have finished this unit of work, you should be able to answer the following questions:
What are the two main differences between physical change and chemical reactions?
What are four signs that new products are formed during a chemical reaction?
Name four ways you can increase the rate of a reaction.
Freezing, melting, evaporation and condensation are all physical changes of state in which molecules of a substance gain or lose kinetic energy. Many common changes that occur around us are actually chemical reactions – when iron rusts, apples go brown, silver tarnishes or copper develops a green tinge, oxidation is occurring. Combustion (burning) is also a form of oxidation. In a chemical reaction new products are formed and this may result in a colour change, a precipitate being formed, the release of gases or energy in the form of light or sound. The following resources may help you to learn about chemical reactions:
Here are 15 rules to remember about using the science laboratories and just a reminder for our Year 7 and 8 students who have used the laboratories before:
No student may enter a laboratory or preparation room except under the direct supervision of the teacher in charge.
The wearing of thongs, sandals, open or other unprotective footwear will not be allowed in any science laboratory at any time. Suitable leather or vinyl shoes are the only acceptable footwear in the laboratory.
Many materials in the laboratory are dangerous and must be used for the purpose stated by the teacher in charge.
Do not try experiments on your own. Do only the experiments assigned according to the instructions given by the teacher in charge.
Never taste chemicals. Smell chemicals only when instructed to do so, and then cautiously in the correct manner.
Never drink from any taps or any vessels in the laboratory.
Always move carefully in a laboratory, and never run.
Never leave a bunsen burner on when not in use.
Gas and water taps and electrical outlets are not to be used unless directed by the teacher in charge.
All accidents (no matter how slight) or breakages must be reported at once to the teacher.
When heating chemicals ina test-tube, point the test-tube away from people. Never look directly into chemical experiments.
A student will not remove nor cause to be removed any item of science equipment from a laboratory.
No bags, ports etc. are to be taken into laboratories.
Before leaving a laboratory, all work areas must be clean and tidy, and any equipment used must be returned to its proper place.
No misbehaviour will be tolerated in the laboratory. Students will be banned from practical work for persistent foolish behaviour.
Your tasks this week will be to create one of the following: