Flashcards in C1 1-8 Deck (27):
What is fractional distillation?
Separating hydrocarbons in crude oil
Give an example of three fossil fuels
Why does fractional distillation work?
Because different hydrocarbons have different boiling points
How does fractional distillation work?
The column is hot at the bottom and cold at the top. The vapours cool as they rise through the column. They condense to form a liquid when they reach a part that is cold enough. The liquid falls into a tray and is piped out of the column.Hydrocarbons with the highest boiling points leave at the bottom of the column. Hydrocarbons with the lowest boiling points reach the top without cooling enough to condense, leaving as gases.
Covalent bonds and intermolecular forces in hydro carbons
The covalent bonds are a lot stronger in hydrocarbons than the intermolecular forces, so they are broken when crude oil is boiled. This makes the molecules separate.
Link between hydrocarbons molecule size, strength of intermolecular forces and boiling point
The larger the hydrocarbon molecules, the stronger the intermolecular forces, and the higher the hydrocarbon’s boiling point. The hydrocarbons with the smallest molecules are gases and those with the largest molecules are solids.
How is tar made?
As crude oil forms, the seabed above it gradually turns to rock. The oil is forced up through the rock. In some parts of the world it eventually reaches the surface. The hydrocarbons with low boiling points evaporate, leaving thick tar behind.
Suggest some problems with drilling for oil?
Oil may spill or leak which can cause oil slicks on the surface of the sea. These can come ashore and damage beaches. It can also damage birds feathers and make their ill or die. Chemicals can be used to break up the oil slick, but this harms wildlife too.
What is cracking?
a chemical process that converts large hydrocarbon molecules into smaller, more useful, hydrocarbon molecules. It involves heating oil fractions to a high temperature and passing them over a catalyst.
What is a fuel?
a substance that reacts with oxygen to release useful energy. This is mostly heat energy.
word equation for the complete combustion of a hydrocarbon:
Hydrocarbon + oxygen = Carbon dioxide + water
What colour does limewater turn when co2 is present?
Difference between complete and incomplete combustion?
Complete combustion happens when there is a lot of air. Incomplete combustion happens when there is not a lot of air.
Word equation for incomplete combustion of a hydrocarbon
hydrocarbon + oxygen → carbon + carbon monoxide + water
7 factors reconsider when choosing a fossil fuel?
- energy value
- ease of use
What is gases make our atmosphere?
Just two gases, nitrogen and oxygen, make up about 99% of the air but also some carbon dioxide, water vapour, and noble gases such as argon.
Give a theory about the formation of the atmosphere?
When they erupt, volcanoes release huge volumes of gases. These are mainly water vapour and carbon dioxide. It is likely that the Earth’s early atmosphere came from gases released from inside the Earth’s crust by volcanoes. The water vapour condensed to form the oceans, leaving an atmosphere of mostly carbon dioxide. There would have been little or no oxygen in the early atmosphere.
Why did Carbon dioxide in the air decrease over the years?
- plants used co2 for photosynthesis and gave out oxygen
- Carbon dioxide is a soluble gas and large amounts of it dissolved in the oceans.
- Carbon dioxide is locked away inside limestone, mainly as calcium carbonate.
2 processes that can increase co2 and decrease oxygen?
Why is co2 increasing?
- Most electricity production and transport uses fossil fuels.
- deforestation - trees may be burnt to clear land, and this releases carbon dioxide.
- With fewer trees left, less carbon dioxide can be removed by photosynthesis.
What makes acid rain?
Sulfuric dioxide is formed when fossil fuels ate burnt. This gas dissolves in the water in clouds, forming acids. The acids make rain more acidic than normal.
What can cause photochemical smog?
When fossil fuels are burnt, sulfuric dioxide is formed. This can react with atmospheric pollutants, especially in sunlight to make photochemical smog.
What do catalytic converters do?
They convert Carbon monoxide to Carbon dioxide in vehicle exhaust systems
Difference between alkanes and alkenes?
Alkenes have a double bond between the carbon atoms.
Saturation in alkanes and alkenes
Alkanes are saturated compounds. They contain only single covalent bonds between their carbon atoms. On the other hand, alkenes are unsaturated compounds. They contain a double covalent bond between two of their carbon atoms.
What is a polymer?
Made when monomers join together