Combustion and properties of Hydrocarbons 4.7.1.3

Question 1

What is combustion?

Answer 1

• where a fuel reacts (or burns) in oxygen.
• it is an exothermic reaction - mostly thermal but also some light and sound.
• also known as oxidation reactions as they are gaining oxygen.

Question 2

What is a hydrocarbon?

Answer 2

A molecule that is only made up of hydrogen and carbon.

Question 3

What does the reaction between hydrogen and oxygen produce?

Answer 3

Hydrocarbon + Oxygen —-> Carbon Dioxide + Water

Question 4

What is complete combustion?

Answer 4

-the burning of a material in a good supply of oxygen. The products are carbon dioxide and water.

Question 5

What is incomplete combustion?

Answer 5

where there is not a plentiful supply of oxygen. As well as carbon dioxide and water forming we also get:

• carbon monoxide
• particles of carbon(soot)

Question 6

How does chain length affect the boiling point of a hydrocarbon?

Answer 6

• as chain length increases so does the boiling point
• a hydrocarbon with a longer chain length has more weak interactions between the molecules. We need energy to break those interactions so boiling point is higher.
• substances that has a high boiling point is less volatile (less easily evaporated).

Question 7

How does chain length affect the flammability of a hydrocarbon?

Answer 7

-As chain length increases, fractions become less flammable.
>the smaller the fraction he fewer the intermolecular forces
so they ignite more easily.

Question 8

How is viscosity affected by the chain length of a hydrocarbon?

Answer 8

-chain length increases, fractions become more viscous, this is due to the increase intermolecular forces between molecules meaning they sticky together more and flow less easily.