random P2 Flashcards
(63 cards)
- What is an Alkane
- What is an Alkene
BOTH INCLUDING THEIR GENERAL FORMULA
- A saturated hydrocarbon (meaning it only has single bonds), general formula CnH2n+2
- An unsaturated hydrocarbon (meaning it has double bonds), general formula CnH2n
Give the first 4 alkanes and alkenes with their general formulas
ALKANES
• Methane, CH4
• Ethane, C2H6
• Propane, C3H8
• Butane, C4H10
ALKENES
• Ethene, C2H4
• Propene, C3H6
• But-1-ene, C4H8
• But-2-ene, C4H8
Are Alkanes or Alkenes more reactive? Explain why
•Alkenes are more reactive
•Because they have a double bond (unsaturated), and this bond can open up to react with other molecules.
• Alkenes only have single bonds (saturated), therefore they are not as reactive.
Describe the test for identifying Alkanes/Alkenes
• If you shake the hydrocarbon with bromine water;
-> An alkene would decolourise/react with the bromine water, due to its double bonds (orange to colourless)
-> Alkanes will not react with bromine water as they only have single bonds (brown colour stays the same)
Alkanes and Alkenes burn in oxygen during complete combustion.
What are the products of this reaction?
• Carbon Dioxide
• Water
What is the reaction called between Alkenes and Bromine Water?
An Addition Reaction
Give 3 ways to measure the ROR
• Precipitation
• Change in Mass
• The Volume of Gas given off
A scientist wants to measure the ROR of two see-through solutions that together produce a precipitate. What experiment should they do?
• Precipitation
1. Put a conical flask on a piece of paper that has a cross on it.
2. Mix the two reactant solutions together in the flask
3. Observe/Time how long it takes for the mark to disappear - the faster the time, the faster the ROR.
What’s a Disadvantage of Precipitation Experiments (to measure the ROR)?
The result is subjective, people might not agree when the mark is exactly obscured.
A scientist wants to measure the ROR in an experiment, but the reaction produces a Gas. What Experiment should they use?
• Change in Mass Experiment
• When gas evaporates, the reaction loses mass, which can be recorded in a mass balance. You know when the reaction has finished when the balance stops changing
Give a Disadvantge of a Change in Mass Experiment (one that produces gas)
Gas is directly released into the open air, which can be dangerous if it’s toxic - therefore this experiment will need a fume cupboard.
How can a Scientist measure the volume of gas given off in an experiment?
• Measure the Volume of gas given off by:
1. Put the reactant in a conical flask, then quickly attach a bung to the flask that’s connect to a gas syringe.
2. The gas evaporated in the reaction will enter the gas syringe and cause it to move; therefore measuring the volume of the gas produced.
3. The reaction will have finished when the gas syringe has stopped moving.
Give four things that can effect the ROR
• Surface Area
• Temperature
• Concentration
• Pressure
How does Surface Area affect the ROR?
Use Marble Chips as an example
The bigger the SA, the faster the ROR. E.g. if you compared the ROR of marble large marble chips vs small marble chips (both at the same mass) then the smaller marble chips will have a faster ROR, as there is more physical surface for the reactants to react with
How does Temperature affect the ROR?
The hotter a reaction, the more energy the particles have. Therefore, the particles collide more as they are moving faster, so reaction happen quicker and therefore the ROR increases.
How does Concentration affect the ROR?
The more concentrated a solution is, the more particles there are. This means that the ROR will increase, as there will be more particles to react with, with also more limited space.
How does Pressure affect the ROR?
When pressure is increased, the amount of space becomes more limited, therefore there is not a lot of space for the particles and so collisions are more frequent, which increases the ROR.
What is Bond Energy?
The energy needed to break a bond or the energy released when a bond forms (energy transfer)
What process are bond breaking and bond making and why?
BOND BREAKING is an endothermic process, because energy needs to be supplied.
BOND MAKING is an exothermic process because energy is released when bonds are formed.
Explain how the Atmosphere was formed
PHASE 1 - Originally, the planet was molten and rocky (like mars) - there was a lot of volcanic activity that released gases like Carbon Dioxide, methane, nitrogen and water vapour into the atmosphere. There was little oxygen, so there was no living organisms.
PHASE 2 - the Earth began to cool, which made the water vapour condense, causing precipitation and forming the oceans. Carbon dioxide dissolved in the oceans. Then plants like algae started to grow from the water, which removed more Carbon dioxide and produced Oxygen. Carbon dioxide got locked up in fossil fuels and sedimentary rocks.
PHASE 3 - The amount of oxygen allowed the evolution of complex organisms.
What is the Atmosphere?
A layer of gases that surround the Earths surface
What’s the Ozone Layer?
When oxygen created a layer in the atmosphere that blocked harmful rays from the sun, this allowed complex evolution to happen.
Why did the amount of Nitrogen in the atmosphere increase?
Ammonia in the atmosphere formed nitrogen when reacting with oxygen and was also released by denitrifying bacteria.
However, nitrogen is not very reactive, it was being made but not broken down/being reacted with. So the levels of Nitrogen increased
What is a greenhouse gas?
A gas in the atmosphere that can absorb and reflect heat radiation
