French term | English term |
Substance chimique | Chemical substance |
Espèce chimique | Chemical species |
Espéce naturelle – espèce synthétique | Natural species – synthetic species |
Odeur – Odorat | Scent – Smell |
réactif | reagent |
Sulfate de cuivre anhydre | Anhydrous copper sulfate |
Gouttes | drops |
Dissoudre | Dissolve |
Tube à essai | Test tube |
Eau distillé | Distilled water |
Amidon | Starch |
Iode | iodine |
Acier galvanisé | Galvanized steel |
Le béton | Concrete |
Eau gazeuse | Carbonated water |
Eau de chaux | Lime water |
Un précipité | A precipitate |
La combustion | A combustion |
Le fer | Iron |
Le cuivre | Copper |
Graisses végétale hydrogénées | Hydrogenerated vegetable fat |
Solution acide | Acidic solution |
Solution basique | Basic solution |
Solution neutre | Neutral solution |
Une boisson | A beverage |
Les propriétés | Properties |
1 - Definition
in Natural Products Most foods and everyday objects are composed of numerous chemical species. In chemistry, it is useful to be able to identify the chemical species present in a food or object.
1 - Using our five senses
The first part of an analysis involves using your five senses: sight, touch, smell, hearing, and taste. However, our five senses are not always enough to identify all of the chemical species
Example: by cutting an apple, a student completed the following table:
some products should neither be smelled nor tasted as they pose health risks.
2 - Trough certain chemical tests
When our senses do not allow us to identify a chemical species, specific tests must be conducted:
Simple Chemical Tests for the detection of certain chemical substances :
2-1 - Test for the presence of water using Anhydrous Copper Sulfate
Anhydrous copper sulfate is a white powder that turns blue in the presence of water.
Procedure:
Test Result: The test is positive if the white powder turns blue. The test is negative if the white powder does not turn blue.
2-2 - Test for the presence of Carbon Dioxide using Lime water
Lime water is a transparent liquid that becomes cloudy in the presence of carbon dioxide.
Procedure: Pass the gas to be tested through lime water.
Test Result: The test is positive if the lime water becomes cloudy. The test is negative if the lime water remains clear.
2-3 - Acidity test using Ph paper
When pH < 7, the solution is considered acidic. When pH = 7, the solution is considered neutral. When pH > 7, the medium is considered basic.
Note: When using a highly colored solution, the coloration of the solution can alter the color of the pH paper and therefore lead to an error in the deduced pH value.
2-3 - Glucose test using Fehling's solution
Fehling’s solution is a blue liquid that, when heated in the presence of certain sugars, produces a brick-red precipitate. This test is specific for the presence of certain sugars, such as glucose, which is a simple sugar
2-3 - Fat test using tracing paper
On tracing paper, fats leave visible greasy stains and marks.
2-3 - Starch test using Iodine solution
Iodine solution is used to detect the presence of starch. In the presence of starch, the slightly brownish iodine solution turns a dark blue color. This dark blue color indicates the presence of starch, which is a complex carbohydrate found in foods like pasta and potatoes.
To highlight certain constituents of lemon juice, the following tests are conducted: