Carbon Unit (Term 4 2022)

Question 1

What is the definition of an organic compound?

Answer 1

-Organic compounds are carbon based compounds containing covalent bonds.

Question 2

What is the definition of a hydrocarbon?

Answer 2

-A hydrocarbon is an organic compound containing only hydrogen and carbon

Question 3

What is the difference between alkanes and alkenes?

Answer 3

-Alkanes contain a single (one) covalent bond between carbon atoms
-Alkenes contain a double covalent bond between carbon atoms
-(Both alkanes and alkenes are families of simple, organic hydrocarbons)

Question 4

What is the definition of an isomer?

Answer 4

-Isomers are compounds with the same molecular formulae but different structural formulae.

Question 5

What is the definition of fossil fuels?

Answer 5

-Fossil fuels are natural fuels formed from dead plants and animals under the sea millions of years ago. They are sources of energy made from heat and pressure acting on dead and decaying organic matter from millions of years ago.

Question 6

What is crude oil?

Answer 6

-Crude oil, a fossil fuel, is a mixture of hydrocarbons of different chain lengths.
-Chain length means the number of carbons in a continuous chain of a hydrocarbon.
-These hydrocarbons have different properties according to their chain length; in particular, different boiling points.

Question 7

What is the definition of mixture?

Answer 7

A mixture is a range of elements mixed together but not chemically joined. An example may be a mixture of salt and sand. Mixtures can be separated. If we want to separate a mixture of sand and salt we simply filter out the sand.

Question 8

What is a boiling point?

Answer 8

-The boiling point of a substance is the ‘energy required to change state from liquid to gas’
-Generally speaking, the smaller molecules have smaller boiling points than the larger molecules.

Question 9

Why do larger molecules have higher boiling points?

Answer 9

-Larger molecules have larger boiling points because the intermolecular bonds have a greater surface area to act upon and therefore more energy is required to overcome the forces of attraction between the molecules.

Question 10

What are intermolecular bonds?

Answer 10

-Between each and every molecule there are intermolecular bonds.
-These forces of attraction need to be overcome when we boil chemical compounds.

Question 11

Describe the process of fractional distillation in the context of crude oil.

Answer 11

-The crude oil is heated. As the molecules reach their boiling point, they rise up the fractioning column and are ‘tapped off’. They are then collected and ready for use.
-The residue (Bitumen) contains the largest molecules with the highest boiling points. These molecules remain in the tower. In summary, fractions with steadily increasing boiling points have been separated.

Question 12

What are fractions (in the context of the unit)?

Answer 12

-Groups of molecules are called fractions. There are several fractions in the mixture that is crude oil. In the process of fraction distillation, these fractions are separated.

Question 13

What is combustion?

Answer 13

-Combustion is the scientific name given to the process of burning.
-In a combustion reaction, fuel is burned and reacts with oxygen to release energy
-The most common way this is seen is through the release of thermal (heat) energy i.e., when burning wood on a fire to keep warm

Question 14

What is the difference between Complete and Incomplete Combustion?

Answer 14

-Complete combustion occurs when there is an excess supply of oxygen
-Incomplete combustion occurs when there is a limited supply of oxygen
-The type of combustion and how much oxygen is present determines what products form
-For compete combustion of hydrocarbons such as methane or octane, the products of the reaction will be carbon dioxide and water
-For incomplete combustion of methane or octane, the products include carbon (soot), carbon monoxide and water.

Question 15

Can incomplete combustion vary?

Answer 15

-There are different possible options when incomplete combustion occurs depending upon the amount of oxygen present
-When there is hardly any oxygen available, the products are carbon and water
-When there is some oxygen available, the products are carbon monoxide and water

Question 16

What are the products formed in complete combustion?

Answer 16

-Fundamentally, for complete combustion to occur, there MUST be an excess of oxygen present.
-The products are Carbon dioxide and water.

Question 17

What is the difference between exothermic and endothermic reactions?

Answer 17

-Reactions which release energy are called exothermic reactions.
-They release energy because the energy stored within the bonds of the reactants is greater than the energy stored within the bonds of the products.
When the bonds break there is a net release of energy in the form of heat and/or light
-Reactions that absorb energy (the opposite of exothermic) are called endothermic reactions
-For endothermic reactions, there is less energy in the bonds of the reactants than the products and so the energy must be absorbed

Question 18

What is the impact of fossil fuel combustion?

Answer 18

-Increase in combustion of fossil fuel has led to an increase in levels of carbon dioxide in the atmosphere
-Carbon dioxide is directly linked to global warming
-It also causes other pollution e.g. Smog (from car exhausts) and Acid rain - this is different to global warming though!
-The increased levels of carbon dioxide on our atmosphere increases the greenhouse effect and causes global warming.

Question 19

What is global warming?

Answer 19

-Global warming refers to the gradual increase in the average temperature in the atmosphere
-It is linked with the increase in concentration of greenhouse gases in the atmosphere
-The heat loss from the Earth to space is slowed down, enhancing the greenhouse effect and leading to global warming
-Greenhouse gases include carbon dioxide, chlorofluorocarbons, methane, nitrous oxides, ozone, water vapour etc.
-Oxygen, nitrogen and neon are NOT greenhouse gases

Question 20

Why is the enhanced greenhouse effect a concern?

Answer 20

-We need greenhouse gases to trap heat and keep the planet warm
-Too much will cause more heat to be trapped which then leads to global warming and other significant impacts.

Question 21

What are the advantages of fossil fuels?

Answer 21

-The fuels are relatively inexpensive
-Fossil fuels have high energy density. This means that if we burn just a little bit of fuel, we get a lot of energy from it.
-Fossil fuels are found readily throughout the world and are accessible

Question 22

What are the disadvantages of fossil fuels?

Answer 22

-Fossil fuels are finite. They are running out because we are using them quicker than they’re being made
-When they are burned, carbon dioxide is produced. They can also produce sulphur dioxide impurities which contribute to acid rain.
-Mining of coal can cause environmental damage

Question 23

What are some advantages of renewable fuels (hydrogen, bioethanol and biodiesel)?

Answer 23

-The fuels are produced at a rate similar to their usage which means we will have a steady supply.
-Burning biofuels releases less carbon dioxide than fossil fuels overall given the photosynthesis involved in growing the crop in the first place.

Question 24

What are some disadvantages of renewable fuels?

Answer 24

-The renewable fuels that contain carbon (bioethanol and biodiesel) will still release carbon dioxide when burned.
-Land space is required to grow crops for bioethanol and biodiesel.
-The isolation of hydrogen gas can be expensive.

Question 25

What are the effects of global warming?

Answer 25

-Thermal expansion of the oceans and melting of glacial ice
-Flooding which can cause the submersion of low-lying cities
-Changes in global climate
-Changes in ocean currents
-Increasing frequency and severity of extreme weather events
-Increase in ocean temperature
-Loss of biodiversity
-Altered disease patterns i.e. epidemics
-Pest could become more active and grow faster