P2.3-P2.6 Flashcards
What’s the mass of a proton?
1
What’s the mass of a neutron?
1
What’s the mass of an electron?
~0
1/2000
What’s the charge of a proton?
+1
What’s the charge of a neutron?
0
What’s the charge of an electron?
-1
Where are the protons in the atom?
Inside the nucleus
Where are the neutrons in the atom?
Inside the nucleus
Where are the electrons in the atom?
Orbiting the nucleus
What does the atomic number of an element represent?
Number of protons (or electrons) in a neutral atom of an element
What does the mass number of an element represent?
Protons+neutrons
What’s an ion?
A pos. or neg. charged particle
What do isotopes of an element have in common with each other?
Same atomic number
same number of protons
What are the differences between isotopes of an element?
Different mass numbers
diff. number of neutrons
What was Rutherford’s experiment with alpha particles?
Alpha particles were fired at a sheet of gold leaf
Particles came off at diff. angles
(most passed through, some deviated, some deflected)
What was the plum pudding model of the atom, accepted before Rutherford’s findings?
Atom= sphere of pos. charged w/ neg. charged electrons dotted within it
What is the expectation that Rutherford had for his experiment?
The alpha particles would smash through the gold leaf like a canon through tissue paper
What is the explanation for Rutherford’s results?
The plum pudding model of the atom was not correct
The atom must have a small dense positive centre
(must be small- the maj. of particles went through undeflected)
Back scatterring- repelled because alpha particles and nucleui are both neg. charged
What is radioactive decay?
When an unstable nucleus breaks down and emits one of 3 types of ionising radiation
What are the 3 types of ionising radiation?
Alpha particles
Beta particles
Gamma waves
Where does the majority of background radiation come from?
Radon gas- from rocks in the ground
What is a half-life of a radioactive element?
The time it takes for the activity to reduce by a half
What are some sources of background radiation?
Rocks- radon gas
Cosmic rays
Medical uses
Living things (absorb radiation from soil)
What happens if ionising radiation gets into living tissue?
It will ionise the atoms that make up DNA and cause mutations
What does ionising radiation have the energy to do?
Ionise atoms?
What is the mass of alpha particles?
4
What is the unit of mass?
amu
What is the mass of beta particles?
0
What is the mass of gamma rays?
0
What is the charge of alpha particles?
2+
What is the charge of beta particles?
1-
What is the charge of gamma rays?
0
What is the unit of charge?
e
What is an alpha particle?
Helium nucleus
What is a beta particle?
Fast moving electron
What is a gamma ray?
Electromagnetic wave
What is the ionising ability of an alpha particle?
High
What is the ionising ability of a beta particle?
Weak
What is the ionising ability of a gamma ray?
Very weak
What are alpha particles stopped by?
Sheet of paper
What are beta particles stopped by?
Sheet of aluminium
What are gamma rays stopped by?
Thick lead
Are alpha particles deflected by a magnetic field?
Yes
Are beta particles deflected by a magnetic field?
Yes (opposite to alpha)
Are gamma rays deflected by a magnetic field?
No
What happens when a nucleus emits an alpha particle?
Looses 2 protons and 2 neutrons
What do decay chains mean about the amount of radioactive elements in the universe?
It’s never fixed
How can people be safe around radioactive materials?
Keep space between the source and the person
Keep exposure time to the source as low as possible
What are alpha particles used for?
Smoke alarms
What form do alpha particles come in when used for smoke detectors?
Aluminium-241
How do alpha particles work in smoke alarms?
Ionise air particles that enter = current
When smoke enters- gets in the way (alpha can’t move through smoke) and reduces air particles being ionised
Reduces current–> sets off alarm
Why does smoke entering a smoke alarm reduce the number of air particles being ionised?
Alpha particles can’t travel through smoke
Why are alpha particles the most useful for smoke alarms?
Highly ionising
Don’t travel well through air
-Won’t harm people living in house if it’s on the ceiling
What are beta particles used for?
Paper mills- to control thickness
How are beta particles used in paper mills?
As the paper is being rolled- beta particles are fired at it with a Geiger-Muller detector on the other side
The thicker the paper- the less radiation detected
-detector will send a message to rollers to adjust pressure according to results
What is the relationship between the number of beta particles being detector by the GM tube and the thickness of the paper in a paper mill?
Thick paper- less particles
Thing paper- more particles
Why are beta particles ideal for use in a paper mill?
Have the ability to pass through paper- but will be obstructed by thicker sheets
What are gamma rays used for?
Sterilising medical equipment
Treating cancer
How are gamma rays used in the sterilisation of medical equipment?
Focused on a sealed packet with the equipment inside
Strong enough to kill any bacteria present
How are gamma rays used to treat cancer?
Focused on a tumour
- in a high enough conc. to kill the cells
Why is the ability to focus gamma rays on a specific part of the body when used in treating cancer useful?
Reduces exposure for healthy tissue
Why are gamma rays ideal for use in radiotherapy?
Travel through skin easily
Strong enough to kill cells
Low ionising ability- low amount of damage
How do nuclear power plants produce electricity?
Nuclear reaction gives off heat Heat evaporates water Water vapour drives the turbine Turbines drives the generator Generator produces electricity
What are the elements commonly used in nuclear power plants to produce electricity?
Uranium
Plutonium
What are the advantages and disadvantages of nuclear power plants as a source of electricity?
Advantages:
Releases less CO2 than fossil fuel plants
Requires less fuel than fosil fuel plants
UK has stores of uranium and plutonium already
Disadvantages:
Produces radioactive waste with half lives of 1000s of years
What is nuclear fission?
The splitting of a nucleus into two smaller nuclei
How does nuclear fission split a nucleus into two smaller nuclei?
By firing a high energy neutron at it
What are the two most common fissionable materials?
Uranium-235
Plutonium-239
How does the process of nuclear fission work?
Neutron fired at a nucleus
= unstable element that breaks into 2
–> releases 3 neutrons
process can continue-=nuclear bomb
What is nuclear fusion?
The joining together of two atomic nuclei to form a large one
Does nuclear fusion form any other products except for a larger nucleus?
NO
What are the conditions needed for nuclear fusion?
V extreme
High pressure and temperature
(not possible on Earth yet)
Are the conditions required for nuclear fusion possible on Earth yet?
NO
How old is the universe?
13.9 billion years old
What are nebulae?
Large clouds of gas and dust in space
How are main sequence stars formed?
Nebulae collapse under their own gravity
Loss of GPE increases KE of gas particles
-increases pressure and temperature until fusion is possible
Heat from the fusion increases the pressure- particles push back away away from gravity pulling them in
–> eventually= settles into equilibrium
= main sequence star
What are the two types of star that a main sequence star could turn into?
Red Giant
(size of sun)
Red Super Giant
What happens to red giants?
–>
white dwarf
–>
black dwarf
What happens to super red giants?
–>
Supernova (explode)
–>
EITHER
Black hole
OR
Neutron star
What charges an atom?
Changing the number of electrons
How is static electricity generated?
When insulators are rubbed together
What is electrostatic charge?
The charge created when electrons from one insulator are moved to another using friction
How does the charge of an object remain on it?
Electrons aren’t free to move
How do charged particles act towards each other?
Opposites attract
What is the relationship between how charged an object is and the amount of potential difference is has?
The more charged- The more p.d
What happens if a charged object has a too big potential difference?
A spark may jump from the object to earth or a conductor that is earthed
How does connecting a metal pipe to the earth with a wire avoid the danger of sparks?
Gives the sparks a fast route to the earth
What are the two types of charge?
Positive
Negative
Why does hair go fluffy after it is combed?
Electrons have exchanged between the hair and comb
-they are attracted to each other (have electrostatic charges)
Describe the function of a LDR
Resistance changes with light
Describe the function of a LED
When current flows in one direction- they light up
Describe the function of a resistor
Resists the flow of electrical charge
Describe the function of a voltmeter
Measures volt. (potential difference)
Describe the function of a diode
Alows the current to flow in one direction
Describe the function of a switch
Prevents the flow of electricty
Describe the function of a lamp
Emits light
Describe the function of an ammeter
Measures amps (current)
Describe the function of a fuse
Disposable circuit breaker
Describe the function of a variable resistor
A resitor who’s resistance can be changed
Describe the function of a battery
Stores energy
What are batteries made up of?
Cells
Describe the function of a thermistor?
Resistance charges with heat
Describe the function of a cell
Makes up a battery
What is potential difference?
Voltage- energy supllied to the charges
What is the unit of potential difference?
Volts
What is the unit charge?
Coulomb
What is a current?
Flow of charge
What is the unit of charge?
Amps
What is resistance?
The ability to prevent a current flowing when a potential differnce is applied
When does the resistance of a wire increase?
The length of the wire increases
The thickness of the wire decreases
When does a current flow?
When charged particles travel through a conductor
-moving electrons can move freely through particles
What is the unit for resistance?
Ohms
What does Ohm’s law state?
Electric current:
Proportional to voltage
Inversely proportional to resistance
What does DC stand for?
Direct current
What does AC stand for?
Alternating current
What happens in DC?
No change in potential difference across battery–> current only flows in 1 direction
(Most portable devices)
What happens in AC?
Change in potential difference as it changes direction smoothly
–> causes current to oscillate back and forth
(Mains)
What colour is the earth wire in a plug?
Green and yellow
What is the function of the earth wire in a plug?
If there is a fault & case becomes live- current passes along
(device is safe)
What colour is the neutral wire in a plug?
Blue
What is the function of the neutral wire in a plug?
Completes the circuit
What is the potential difference of the neutral wire in a plug?
0v
What colour is the live wire in a plug?
Brown
What is the function of a live wire in a plug?
Provides energy for the device
What is the potential difference of a live wire in a plug?
230v
What is Kirchoff’s 1st law?
Sum of current in = Sum of current out
Is the current in a series circuit equal in all parts?
Yes
Is the current in a parallel circuit equal in all parts?
No- current is split between branches
What does potential difference do in a series circuit?
Splits equally between all components
somehow knows how many
What does potential difference do in a parallel circuit?
Is equal in every branch
What is Kirchoff’s 2nd law?
Sum of potential difference from cell = Sum of potential difference in each branch
What does resistance do in a series circuit?
(bridge analogy- wider bridge= less resistance, one after another=slower
)
Rt=R1+R2
What does resistance do in a parallel circuit?
(two bridge analogy- two to choose from for a big group- faster)
1/Rt=1/R1+1/R2
What is the relationship between the resistance and the temperature in a filament lamp?
Directly proportional
-resistance increases as temperature increases
What is the relationship between the resistance and the temperature in a thermistor?
Inversely proportional
-resistance falls as temperature increases
What is the relationship between the resistance and the temperature in an LDR?
Inversely proportional
-resistance falls as light intensity increases
What is the relationship between the thickness of a wire and the current it can bear?
Directly proportional
-thicker the wire, greater the current it can bear
What is the function of a control rod in a nuclear reaction?
To absorb neutrons
slows chemical reaction down to control it
What are the three effects when two forces act upon an object?
Compression
Tension
Torsion
