PBSci3a Module 2: Physical Properties of Oils

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Questions and Answers

What is the state of oils at room temperature?

Solid

Gas

Liquid (correct)

Crystalline

Which property is not associated with pure oils?

Greasy feel

Odorless

Tasteless

Solid state (correct)

Which of the following statements about lipids is true?

They are esters of short chain fatty acids.

They are found only in plants.

They are present in all living organisms. (correct)

They are only soluble in polar solvents.

In which solvents are lipids highly soluble?

Ether Signup and view all the answers

What kind of odor is associated with the formation of acrolein?

Pungent irritating odor Signup and view all the answers

What makes lipids a structural source of energy?

Their long chain fatty acids Signup and view all the answers

Which of the following is a characteristic of fats, but not oils?

Solid at room temperature Signup and view all the answers

Which chemical is a dehydrating agent mentioned in the content?

KHSO4 Signup and view all the answers

What is the primary color characteristic of pure lipids?

Colorless Signup and view all the answers

Which of the following processes does NOT involve emulsification of fats?

Acrolein formation from fats Signup and view all the answers

What is the role of albumin as mentioned in the text?

Emulsifier Signup and view all the answers

Which statement about lipids' solubility is false?

Lipids can dissolve in water. Signup and view all the answers

Which of these reactions involves margarine and an acid?

Dil HCl + Margarine Signup and view all the answers

Which taste characteristic applies to pure lipids?

Tasteless Signup and view all the answers

What is a common consequence of the rancidification of fats/oils?

Decreased shelf life Signup and view all the answers

What is the main reason lipids are categorized as non-polar compounds?

They do not mix with polar substances. Signup and view all the answers

Which pair of substances can lead to acrolein formation when combined with fats?

KHSO4 and fat Signup and view all the answers

What type of reaction occurs when alcohol is combined with coconut oil?

Emulsification Signup and view all the answers

Which components are involved in the production of DCM + coconut oil?

HCl and coconut oil Signup and view all the answers

Which of the following is a characteristic of the effects of fats/oils?

Decrease in surface tension Signup and view all the answers

What is the primary purpose of the iodine number in the context of fats and oils?

To assess the degree of unsaturation of fatty acids Signup and view all the answers

Which test would yield a bluish-red to purple color when testing for cholesterol?

Salkowski's test Signup and view all the answers

What type of emulsion is produced when coconut oil is combined with Na2CO3 and water?

Temporary emulsion Signup and view all the answers

What is the outcome of the glycerol test via acid dehydration?

Production of acrolein Signup and view all the answers

Which statement is true about the halogenation reaction in testing oils?

It monitors the reduction of double bonds Signup and view all the answers

How is the iodine value expressed in relation to fats and oils?

In terms of grams of Iodine absorbed per 100 grams of fat or oil Signup and view all the answers

What is the final product when rancid oil is mixed with Na2CO3 and water?

Temporary emulsion Signup and view all the answers

What color shift indicates a positive result for the Liebermann Burchard test?

Red or pink to bluish-green Signup and view all the answers

Which factor affects the absorption characteristics of iodine in unsaturated fatty acids?

Number of double bonds Signup and view all the answers

Which emulsion is described as 'permanent' in the given experiments?

Rancid oil combined with albumin Signup and view all the answers

Study Notes

Physical Properties of Oils and Fats

Oils are liquids at room temperature, while fats are solid.
Both oils and fats have a greasy feel and are colorless, odorless, and tasteless in their pure forms.

Definition and Composition of Lipids

Lipids are esters formed from long-chain fatty acids and alcohols.
They are waxy or oily substances found in all living organisms.
Lipids are non-polar and insoluble in polar solvents like water but soluble in non-polar solvents like ether, chloroform, benzene, and acetone.

Solubility of Lipids

Lipids do not dissolve in water but dissolve well in organic solvents, collectively known as "lipid-solvents" or "fat-solvents."

Rancidification

Rancidification involves the formation of acrolein (propenal), which has an acrid odor.
Dehydrating agents like KHSO4 (potassium bisulfate) and MgSO4 can promote this process.

Emulsification of Fats

Albumin can act as an emulsifier, stabilizing mixtures of oil and water.
Temporary emulsions form when coconut oil mixes with water directly or with sodium carbonate.
A stable emulsion can occur when rancid oil is mixed with water and albumin.

Halogenation Reactions

Halogenation involves reactions with bromine and iodine, potentially used for testing the presence of unsaturation in fats and oils.

Tests for Cholesterol

Salkowski's test shows a color change from bluish-red to purple.
Liebermann-Burchard test uses acetic anhydride and sulfuric acid, resulting in a color change from red or pink to bluish-green to indicate cholesterol presence.

Test for Glycerol

Glycerol can be converted to acrolein through acid dehydration.

Iodine Number (Value)

The iodine number measures unsaturation in fats and oils, indicating the grams of iodine that react with 100 grams of fat.
Unsaturated fatty acids absorb iodine at double bonds until fully saturated, providing insight into the degree of unsaturation in a sample.

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Description

This quiz focuses on the physical properties of oils, specifically examining their appearance, consistency, color, odor, and taste. It is designed for students to understand the characteristics of oils at room temperature. Test your knowledge of these essential attributes.