Separating mixtures

 

Foods are great examples of mixtures. Chips are particularly interesting as they contain saturated and unsaturated fats, carbohydrates, such as starch, salt and flavour additives.

The quantities of each additive are listed on the package, as shown on the right.

In this investigation we will separate the salt and fats from chips, calculate the percentage amount and compare it to the package label.

 
1) Take a sample of chips and crush them using a mortar and pestle.

 
2) Measure approximately 7.00 grams of the crushed chips into an evaporating dish.

 

3) Using a measuring cylinder measure approximately 25 mL of acetone and add it to the evaporating dish with the crushed chips. Use a glass rod to stir for 5 minutes.

Acetone will dissolve the fat.

 

 
4) Filter the contents of the acetone and crushed chips into a 100 mL beaker. Make sure all the crushed chips are transferred into the filter paper. Rinse the residue with a further 10 mL of acetone to remove all the fat.

 
5) Weigh an empty, clean evaporating dish.

 
6) Transfer the filtrate containing the fat and acetone into the evaporating dish and allow to stand in a fume cupboard for an hour. The acetone will evaporate leaving just the fat.

 

7) Once the acetone has evaporated weigh the evaporating dish with the fat.

If the fat appears to be solid at room temperature it is most likely a saturated fat.

If it is a liquid it is predominantly an unsaturated fat.

Using the data from the label. shown above, calculate the percentage, by mass, of fat in the chips.

Solution

Using the results shown here calculate the percentage, by mass, of fat in the chips.

Solution

How do the results compare? Give an explanation
The questions below are for senior chemistry students  
1) Is acetone polar or non-polar? Explain

2) Explain why acetone is mildly soluble in water and also able to dissolve fats.

 

  
3) What is meant by the following terms.

a) Saturated fats.
b) Unsaturated fats.		  

4) Explain why unsaturated fats would be liquid at room temperature while saturated fats would be solid. Use the two molecules shown on the right in your explanation.

Use the words

- intermolecular bonding

- dispersion forces

- saturated

- unsaturated

- polar

- non-polar
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