# Physics: Structured Paper P3 - Topic 5

Yehhh revision :)

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## Kinetic Theory and Temperature in Gases

Gases are randomly moving particles!
> Very Small Particles
> Constantly Moving
> Collide with eachother all the time

Absolute Zero is as cold as stuff can get - 0 Kelvin
COLDEST EVER = -273 KELVIN
To convert from C to K just add 273. :)

Kinetic Theory is proportional to Temperature
The temperature of a gas (in kelvins) is proportional to:
the average kinetic energy of its particles.

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## Pressure in Gases

Constant = Pressure ÷ Temperature (in K)

p1/t1 = p2/t2

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## Particles In Atoms

ALPHA:

• HELIUM NUCLEUS
• SLOW AND HEAVY
• STRONGLY IONISING
• STOPPED BY PAPER

BETA:

• AN ELECTRON
• LIGHT AND FAST
• MODERATELY IONISING
• STOPPED BY THIN METAL

GAMMA:

• NO MASS, VERY FAST
• WEAKLY IONISING
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NEUTRON RADIATION= neutrons - very penetrating!

NEUTRONS ARE DIFFICULT TO DETECT BECAUSE THEY'RE NEUTRAL.
HERES WHY:

• Charged particles knock electrons off atoms, ionising them.
• LOSS OF ELECTRONS = IONISING
• They also move towards charged objects.
• You can use an electrical field to deflect a beam of alpha particles.
• NONE OF THIS WORK FOR NEUTRONS- they are detected by looking for nuclear decays.
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## Particles in Atoms

A nucleus will be unstable if it has:

• too many neutrons/too few neutrons
• if its too heavy eg. to many protons and neutrons together
• too much energy

β - ) decay happens when there are too many neutrons, the proton number decreases by one, and the nucleon number stays the same.

β + ) decay happens when there are too few neutrons, the proton number decreases by one, and the nucleon number stays the same.

α ) decay happens in heavy nuclei, the proton number decreases by two, and the nucleon number decreases by four.

γ ) is emitted from a nuclei with too much energy.

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## Fundamental and Other Particles

Electrons and Positrons are fundamental particles.
This means you can't divide them into smaller particles.

Scientists can recreate fundamental particles by colliding particles at a very high speed. This produces an equal amount of matter and anti-matter made of anti-particles.

Each particle has an anti-particle which has the same mass, but opposite charge.

Protons and Neutrons are NOT fundamental particles.

Proton = UUD | Neutron = DDU

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## Electron Beams

USED FOR TV SCREENS >>>

• The heater heats the cathode and gives energy to the electrons.
• They're pulled towards the positive anode.

Calculating the kinetic energy of each electron..

kinetic energy (j) = charge of electron (in coulombs) x accelerating voltage (volts)

and, the size of the current produced..

current (l) = charge (n x e) ÷ time (t)

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## Electron Beams 2

An electron beam is attracted by a positive charge, and repelled by a negative charge.

Electron guns are used in TV's, Oscilloscopes, and to make X-Rays.

An Oscilloscope is a device for displaying the voltage and frequency of an electrical signal.
> = time / ^ = voltage

xrays = tungsten target.

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