Flashcards in P2.5 Deck (27)
If an atom of carbon has an atomic number of 6 and a mass number of 14 what does that tell us about the number of protons, electrons and neutrons?
it tells us that there are
What is meant by ionisation?
Losing or gaining electrons
State what an alpha and a beta particle are made of?
Helium nucleus - 2p +2e
High speed electron
Which type of radiation is most ionising and which is most penetrating?
Alpha and Gamma
What is produced during the fission of Uranium 235?
2 daughter nuclei
2 or 3 neutrons
Lots of energy released
Explain the difference between nuclear fission and nuclear fusion.
Nuclear fission is the splitting of a large nucleus whereas, nuclear fusion is the joining of a small nucleus.
Describe the process where the energy from a nuclear reactor core is converted into electrical energy (5 steps).
1) Heat energy transferred to the coolant, which is usually water.
2) This super-heated water is pumped to a heat exchanger where it is used to generate steam.
3) The steam turns a turbine.
4) Then it turns a generator.
5) Then it turns kinetic energy into electrical energy.
What is meant by a "controlled nuclear chain reaction."
When some of the neutrons released by fission of Uranium 235 are absorbed by other materials, meaning only one of the two neutrons released goes on to be absorbed by another Uranium 235 nucleus, limiting the amount of energy released.
What problem is associated with the products of nuclear fission?
Define nuclear fusion.
The creation of large nuclei from small nuclei accompanied by the release of lots of energy.
By what process do stars obtain their energy?
Why does nuclear fusion only happen at high temperatures and pressures?
It is needed to overcome the electrostatic repulsion of protons.
What are the two main dangers of ionising radiation?
Tissue damage and possible mutations of DNA.
Thorium and radium used to be put in face creams in the 1900'. Why is this not done now?
Scientists became aware of the hazards and risks.
How can nuclear waste be stored and disposed of in the long term?
Stored in concrete, steel and glass containers.
What is the main advantage of nuclear power over fossil fuel power stations?
No CO2 is released.
What is the disadvantage of storing nuclear waste in space? in the sea?
Container could fall back to earth.
Container could corrode and leak.
What is the half life of this substance?
What is the half life of an isotope
The time taken for the activity of a sample to half or time for half the undecayed nuclei to decay.
What is meant by background radiation and where does it originate?
The natural radiation level around us from space, ground and rocks, radon gas.
How is radiation used to gauge the thickness of paper?
A detector counts the rate at which beta particles pass through paper. If it is too high or too low the paper isn't the right thickness.
How is radiation used in smoke alarms?
Alpha particles from Americium-241 ionise the air to make ions and electrons. A current flows between two charged plates. When smoke gets in the air gaps, the current falls and sounds the alarm.
How are stars formed?
Stars form when dust and gas are pulled together through gravitational attraction.
Explain why the early Universe only contained Hydrogen but now contains a wide variety of elements.
Elements other than hydrogen and helium were made in Super novae (exploding stars).
Describe the forces acting on a star during the main sequence period of its life.
It is stable because the forces within it are balanced by pressure within the star.
Describe the stages of a smaller star.
Nebulae - star - Red Giant - White Dwarf.