exam questions i got wrong Flashcards
describe the process of nuclear fission inside a nuclear reactor
- neutron absorbed by a nucleus
- nucleus splits into two (smaller) nuclei
- and 2/3 neutrons are released
- and gamma rays are emitted
name two sources of man-made background radiation
- radioactive waste
- x-rays
- radiotherapy
- nuclear weapons (testing)
explain how the process of nuclear fusion leads to the release of energy
- lighter nuclei join to form heavier nuclei
- some of the mass of the nuclei is converted to energy of radiation
explain why contamination of the inside of the human body by a radioactive material that emits alpha radiation is highly dangerous
- alpha radiation is highly ionising
- causing an increased risk of cancer
- until the radioactive material is removed
OR - activity of radioactive material reaches background radiation levels
explain the ideal properties of a radioactive source for use in medical diagnosis
- short half-life
- (short half-life means) less damage to cells
- low ionising power
- (low ionising power means) less damage to cells
- highly penetrating
- (highly penetrating means) it can be detected outside the body
- emits gamma radiation
explain what happens in the process of nuclear fusion
- light nuclei
- join to form a heavier nucleus
- some of the mass of the nuclei is converted to energy
explain how the paths of the alpha particles were used to develop the nuclear model of the atom
- most alpha particles pass straight through the atom
- which shows that the atom is mostly empty space
- very few alpha particles are deflected through a large angle
- which shows the atom contains a nucleus where the mass / charge of the atom is concentrated
explain how the distance at which an electron orbits the nucleus may be changed
- electron may absorb electromagnetic radiation
- and move further from the nucleus
- to a higher energy level
why are biofuels only carbon neutral in theory
- often have to clear land by cutting down trees to grow biofuel
- trees no longer photosynthesise and absorb co2
- trees will release co2 if burned
- energy required to harvest, process and transport biofuels
- this releases more co2
after 1 hour, the temperature of the room has become constant, even though the heater is still switched on. explain why.
- the room is losing energy/heat
- at the same rate as the heater supplies it
structure of a vacuum flask
- plastic cap
- double-walled glass container
- vacuum
- silvered surfaces
it is designed to reduce the rate of energy transfer by heating processes. describe how the design keeps the liquid inside hot
plastic cap:
- plastic is a poor conductor
- stops convection currents forming at the top of the flask so stopping energy transfer by convection
- particles evaporating from the hot liquid cannot move into the air so stops energy transfer by evaporation
glass container:
- glass is a poor conductor so reducing energy transfer by conduction
vacuum:
- both conduction and convection require a medium
- so stops energy transfer between the two walls by conduction and convection
silvered surfaces:
- reflect infrared radiation
- poor emitters of infrared radiation
- infrared radiation partly reflected back towards hot liquid
- reduce energy transfer by radiation
explain, in terms of particles, how evaporation causes the cooling of water
- fastest particles have enough energy
- to escape from the surface of the water
- therefore the mean energy of the remaining particles decreases
- the lower the mean energy of particles the lower the temperature of the water
it is unlikely that all of the electricity that the uk needs can be generated by solar power systems. explain why
- a really large area would need to be covered with solar cells
- due to low useful power output / efficiency of solar cells
at the bottom of the slide, all riders and their sleds have approximately the same speed. explain why
- 1/2mv^2 = mgh
OR - decrease in Ep = increase in Ek
- masses cancel on both sides of the equation
OR - v^2 = 2gh
- final speed only depends on vertical height and gravitational field strength
- variations will be due to air resistance/friction
OR - different initial speed
give two environmental advantages of using gas over coal to generate electricity
- no sulfur dioxide released
- doesn’t cause acid rain
- no particulates released
- doesn’t cause global dimming
- less carbon dioxide released
- less global warming
- no solid waste
- gas mining is less destructive than coal mining
