If you have a glass of salty water and a glass of sugary water, how do you tell which is which? The easiest way is to taste them. Your tongue is actually a very clever chemical laboratory. But, if you don’t know what a liquid is, it is best not to taste it. It might be poisonous! Finding out what things are made of is called chemical analysis. Scientists have developed a whole range of tests to help them do this.
Chemical analysis is used to test for all kinds of things. Chemists test drinking water to see if it has been polluted with dangerous chemicals. In hospital, biochemists test sample of blood, saliva and urine from the patients. They are looking for the chemicals that show someone has a particular illness. Forensic chemist helps the police, for example, by checking for poison in the body of a murder victim.
Flame and fire
One of the simplest chemical tests is to check the presence of a metal in a sample. All you need to do is burn a tiny amount of sample and look at the colour of the flame. Different metal burn with different colours, for example, calcium has an orange-red flame, While potassium burn lilac. Burning is also used to analyse organic compounds (chemical containing carbon). The method involves burning a sample of the compound until it breaks down into its individual elements (basic substances). Scientists can then measure how much there is of each of the common elements in organic compounds, carbon, hydrogen, oxygen and nitrogen.
Changing colours
Chemists use various substances to check for the presence of particular chemicals. These substances called called indicators, change colour if the chemical is present. Iodine in solution has a purplish colour, but if you put a drop onto something containing starch, the solution will turn black. Another important indicator is special paper called litmus paper. It turns red if touched by an acid, and blue if touched by an alkali (the chemical opposite of an acid).
Another technique using colour is called chromatography. A simple experiment using chromatography shows what’s in the coloured coatings of some sweets. Dissolve the coating of the sweet in a little bit of water. Then put a drop of solution onto blotting paper. You will see that there are actually different colours, each one spreading out from the drop at a different speed. You are left with a series of coloured rings, one for each of the chemicals in the coating of the sweet.
Using spectra
White light is actually made up of different colours, called the spectrum. If you shine white light through a thin slice of material, the light will be broken up into different colours in a particular way. Scientists can use this to spot particular substances or elements. This technique is called spectroscopy. Other forms of radiation, including infrared, ultraviolet and X-rays, can also be used this way.
Mass spectrometry is one of the most powerful ways of analyzing many kinds of chemical. In this technique, a substance is broken up into charge fragments, and electric and magnetic fields are used to measure the mass (weight) of each fragment. Different compounds have their own characteristic mass spectrum, which can be used to identify them.
Chemical analysis is used to test for all kinds of things. Chemists test drinking water to see if it has been polluted with dangerous chemicals. In hospital, biochemists test sample of blood, saliva and urine from the patients. They are looking for the chemicals that show someone has a particular illness. Forensic chemist helps the police, for example, by checking for poison in the body of a murder victim.
Flame and fire
One of the simplest chemical tests is to check the presence of a metal in a sample. All you need to do is burn a tiny amount of sample and look at the colour of the flame. Different metal burn with different colours, for example, calcium has an orange-red flame, While potassium burn lilac. Burning is also used to analyse organic compounds (chemical containing carbon). The method involves burning a sample of the compound until it breaks down into its individual elements (basic substances). Scientists can then measure how much there is of each of the common elements in organic compounds, carbon, hydrogen, oxygen and nitrogen.
Changing colours
Chemists use various substances to check for the presence of particular chemicals. These substances called called indicators, change colour if the chemical is present. Iodine in solution has a purplish colour, but if you put a drop onto something containing starch, the solution will turn black. Another important indicator is special paper called litmus paper. It turns red if touched by an acid, and blue if touched by an alkali (the chemical opposite of an acid).
Another technique using colour is called chromatography. A simple experiment using chromatography shows what’s in the coloured coatings of some sweets. Dissolve the coating of the sweet in a little bit of water. Then put a drop of solution onto blotting paper. You will see that there are actually different colours, each one spreading out from the drop at a different speed. You are left with a series of coloured rings, one for each of the chemicals in the coating of the sweet.
Using spectra
White light is actually made up of different colours, called the spectrum. If you shine white light through a thin slice of material, the light will be broken up into different colours in a particular way. Scientists can use this to spot particular substances or elements. This technique is called spectroscopy. Other forms of radiation, including infrared, ultraviolet and X-rays, can also be used this way.
Mass spectrometry is one of the most powerful ways of analyzing many kinds of chemical. In this technique, a substance is broken up into charge fragments, and electric and magnetic fields are used to measure the mass (weight) of each fragment. Different compounds have their own characteristic mass spectrum, which can be used to identify them.
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