Margarine is made by hydrogenating vegetable oils so that they take on the consistency of butter. Propose a chemical basis for this change from a liquid to a solid.

Question

A.  Hydrogenation of fats changes them from saturated to unsaturated, which are more solid.
B.  Trans-fatty acids are changed from unsaturated to saturated, allowing them to solidify.
C.  Trans fatty acids are changed from saturated to unsaturated, allowing them to solidify.
D.  Hydrogenation of fats changes them from unsaturated to saturated, which are more solid.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

Gather Content
· What do you know about the effect of saturation on the consistency of a fat? How does it relate to the question?

Consider Possibilities  
· What other information is related to the question? Which information is most useful?

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

D.  Hydrogenation of fats changes them from unsaturated to saturated, which are more solid.


Clarify Question
· What is the key concept addressed by the question?
        o The question asks about the effect of hydrogenating an oil on its consistency.
· What type of thinking is required?
        o You are being asked to apply your knowledge of the effects of hydrogenation of fats on consistency.
· What key words does the question contain and what do they mean?
        o Hydrogenating vegetable oil – this refers to adding more hydrogens to an unsaturated fat to make it more saturated.  This can also lead to the formation of trans fats.
        o Trans-fatty acids – these are the product formed when unsaturated fatty acids are hydrogenated.

Gather Content
· What do you know about the effect of saturation on the consistency of a fat? How does it relate to the question?
        o Saturated fats do not have C=C double bonds, so their fatty acid tails can compact together tightly.  This makes them more likely to be a solid at room temperature.  Butter is a good example of a saturated fat.  If heat is added the butter can melt from a solid to a liquid.
        o Unsaturated fats have C=C double bonds that introduce kinks or bends into the fatty acid tails.  This prevents the fats from getting as close to each other, which makes them more likely to be a liquid at room temperature.  Corn oil is a good example of this, if the oil is put in a freezer it will eventually form a solid.

Consider Possibilities  
· What other information is related to the question? Which information is most useful?
        o Adding hydrogens to an unsaturated fat will make it have fewer bends and make it more solid.  These hydrogenated unsaturated fats are often trans-fats.

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o The correct answer is that hydrogenation of fats changes them from unsaturated to saturated, which are more solid.  why trans-fatty acid answers are not correct because these are the products of hydrogenation.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked you to apply the structure of a fat to predict its melting temperature. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you recall what was meant by unsaturated fat, saturated fat, and trans-fat?  Did you understand the impact of saturation on how solid a fat would be?  Did you recall that trans-fats and saturated fats are made by hydrogenating unsaturated fats.