Question

lipids are soluble (dissolve) in oil but are insoluble (dont dissolve) in water. when mixed with water, the lipid will float on top to form a separate layer. to test for the presence of lipids in food, the sample is placed on a piece of brown or newspaper, and then the paper is held up to the light. a test that is positive for lipids will have a oily spot that is translucent, or clear, on the paper. 26. what does soluble mean? 27. explain the solubility of lipids. 28. how would you test for lipids, and what is a positive result?

Explanation:

Question 26

"Soluble" means a substance can dissolve in a solvent. For lipids, being soluble in oil means they mix well with oil, and insoluble in water means they don't mix with water.

Lipids are non - polar molecules. Oil is also non - polar, and water is polar. According to the principle "like dissolves like", non - polar lipids dissolve in non - polar oil, while they do not dissolve in polar water.

• Testing method: Take a sample of the food suspected to contain lipids. Rub it on a piece of brown or newspaper. Then hold the paper up to the light.
• Positive result: If there is a translucent (or clear) oily spot left on the paper after rubbing the food sample and holding it to the light, it indicates the presence of lipids. This is because lipids, being insoluble in water (the water in the paper will not wash away the lipid spot) and having the property of making the paper translucent when present, leave such a spot.

Answer:

Soluble means a substance can dissolve in a particular solvent (e.g., lipids dissolve in oil).

Question 27