Question 1

What are alkenes and how do they differ from alkanes in Organic Chemistry?

Accepted Answer

Alkenes are a class of hydrocarbons that contain at least one carbon-carbon double bond, which distinguishes them from alkanes that only have single bonds. This double bond makes alkenes unsaturated, allowing them to undergo addition reactions. In the Cambridge IGCSE Coordinated Science curriculum, understanding the structural differences between alkenes and alkanes is fundamental to studying Organic Chemistry.

Question 2

How can you test for the presence of an alkene in a chemical sample?

Accepted Answer

To test for the presence of an alkene, you can use the bromine water test. When bromine water, which is orange, is added to an alkene, the solution becomes colorless. This reaction occurs because the alkene's double bond reacts with bromine, breaking the double bond and forming a dibromo compound. This test is a key practical skill in the Cambridge IGCSE Coordinated Science curriculum.

Question 3

What is the general formula for alkenes and how is it used?

Accepted Answer

The general formula for alkenes is CnH2n, where 'n' represents the number of carbon atoms. This formula helps in determining the molecular structure of any alkene. For example, if n=2, the alkene is ethene (C2H4). Understanding this formula is essential for students studying Organic Chemistry in the Cambridge IGCSE Coordinated Science syllabus.

Question 4

Why are alkenes considered more reactive than alkanes?

Accepted Answer

Alkenes are more reactive than alkanes due to the presence of the carbon-carbon double bond. This double bond is a region of high electron density, making it more susceptible to attack by electrophiles in addition reactions. This reactivity is a crucial concept in Organic Chemistry, particularly in the Cambridge IGCSE Coordinated Science curriculum, where students explore various chemical reactions.

Question 5

What are some common uses of alkenes in industry?

Accepted Answer

Alkenes are widely used in the chemical industry as starting materials for the production of polymers, such as polyethylene and polypropylene, through polymerization reactions. They are also used in the manufacture of alcohols, detergents, and other chemicals. Understanding these applications is part of the Cambridge IGCSE Coordinated Science curriculum, highlighting the practical importance of Organic Chemistry.

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