C3 Flashcards
What is an exothermic reaction?
One which gives out energy usually in heat
How is an exothermic reaction shown?
A rise in temperature
What is an example of an exothermic reaction?
Combustion
What is an endothermic reaction?
One that takes in energy, usually in heat
How is an endothermic reaction shown?
A fall in temperature
What is an example of an endothermic reaction?
Thermal decomposition
How do you decide whether a reaction is endo or exo?
You can measure the amount of energy produced by taking the temperature of the reactants and mix in a polystyrene cup and measure the temperature of the solution at the end
What happens during a chemical reaction?
Old bonds are broken and new bonds are formed
Is bond breaking an exothermic or an endothermic reaction?
Endothermic because energy is supplied
Is bond making an exothermic or an endothermic reaction?
Exothermic because it releases energy when formed
Explain the calorimetric method ued to measure the energy content of fuels
- Reduce draughts so as much heat as possible goes into heating the water eg. use a screen
- Put fuel in spirit burner and weigh
- Measure water into a copper calorimeter
- Take initial temperature of water and light wick
- When water temperature has raised by 20?30 degrees, note the highest temperature of water
- Reweigh the burner
- Repeat if comparing fuels
What is the equation for energy given out per gram?
Energy per g = energy released / mass of fuel burnt
Name 4 ways to keep the calorimetric test fair
Same equipment
Same amount of water
Water initial and final temperatures = same
Repeat
Give an example of a slow chemical reaction?
Rusting
Give an example of a fast chemical reaction?
Burning
The rate of reaction that produces a gas can be observed by measuring how quickly the gas is produced. Name two ways of doing this.
? Measure the change in mass = mass falls as gas produced
? Measure cm(cubed) of gas given off = gas syringe
Must do these at regular intervals
What two things does the rate of reaction depend on?
Explain why
Collision frequency = more collisions = faster
Energy transferred in collision = enough energy to be successful
What effect does an increase in temperature have on collisions?
They move quicker = more collisions
Increases energy of collisions = more successful collisions
What effect does an increase in concentration or pressure have on collisions?
More particles in the same space = closer together = more collisions
What effect does an increase in surface area have on collisions?
More surface area exposed = more area to work on = collisions will increase
What effect does a catalyst have on collisions?
Provides surface where reactions can take place.
Lowers the activation energy (reduces the energy needed by particles to react)
What is the equation for atom economoy?
Atom economoy = Total Mr of desired products / Total Mr of all products (x100)
Why does a high atom economy benefit the environment?
Reactions with low atom economy use up resources very fast
Make lots of waste = has to be disposed of = unsustainable
How does atom economy effect profits?
The lower the atom economy = aren’t profitable because expensive to buy materials and waste products can be expensive to dispose responsibly of
What is the equation for percentage yield?
Percentage yield = actual yield (g) / predicted yield (g)
x100
Give four reasons for why yields are always less than 100%?
? Evaporation
? Filtration (solid/liquid some left behind)
? Transferring liquids (some remain on inside of old container)
? Not all reactants make a product
Give 2 advantages of batch production
Flexible = several different products made using the same equipment
Low start up costs
Give 2 disadvantages of batch production
Labour intensive
Difficult to obtain the same quality in each batch
Give 3 advantages of continuous production
Never stops = no time is wasted emptying reactors and setting up again
Runs automatically
Quality is always consistent
Give a disadvantage of continous production
Start up costs are very high
Give an example of a product made by batch production
Pharmaceutical drugs
Give an example of a product made by continous production
Ammonia (haber process)
What is the pharmaceutical drug making process?
? Research and development
? Testing/trialling to ensure it works and is safe
? Manufacture
What two things make drugs expensive to make?
? Raw materials (extracted from plants)
? Energy
How do you extract a substance from a plant?
It has to be crushed, boiled and dissolved in a suitable solvent
Then use chromatography to extract the substance you want
How can you tell if a substance is pure with chromotography?
It won’t be seperated by chromotography (one blob)
How can you tell if a substance is pure by the boiling/melting points of thesubstance?
They have specific melting points
If a substance is impure, the melting point will be too low and the boiling point too high
Give four properties of diamond
Lustrous
Colourless
Strong covalent bonds = high melting point
Doesn’t conduct electricity
What makes diamond very hard?
Each carbon atom forms four covalent bonds in a very rigid giant covalent structure = very hard
Why is diamond useful as a cutting tool?
?Really hard because of giant covalent structure
?Has a high melting point
Give five properties of graphite
Black Opaque Shiny High melting point Conducts electricity
Explain the structure of graphite
Each carbon atom only forms three covalent bonds, creating sheets of carbon atoms which are free to slide over each other
Why can graphite conduct electricity?
Since only 3 out of each carbons 4 outer electrons are used in bonds, there are lots of delocalised electrons which move
What three properties do all giant molecular structures share?
Strong, high melting points and don’t dissolve in water
What are fullerenes?
Molecules of carbon shaped like closed tubes/hollow balls
What is a use of a fullerene?
To cage” other moleculs = eg. new way of delivering a drug to the body for slow release?”
What can fulluerenes be joined together to make?
Nanotubes which are tiny hollow carbon tubes
What is a use of a nanotube?
Have a large surface area = industrial catalysts
