PHSYICS RADIOACTIVITY AND ATOMIC STRUCTURE TEST REVISON

PHSYICS RADIOACTIVITY AND ATOMIC STRUCTURE TEST REVISON

1. Pressure in gases

   • Particle collisions cause a net. force at right angles to a surface/the surface they are hitting.
   • As pressure increases, temperature increases.
   • Gases at a constant temperature
     • As volume decreases, the pressure will increase as the particles will have more collisions in an enclosed space.
   • HIGHER
     • Compressing the gas does work on the gas, if compressed slowly, energy transfers to the surroundings and the gas remains at a constant temperature.
       • 'DOES WORK' = moving something using a force

2. EQUATIONS TO REMEMBER FOR THIS TEST

   • BOYLES LAW
     • pressure x volume = constant
     • pV =constant
     • Pressure in Pa or N/m^2 Volume in m^3
       • p1xV1 = p2xV2
   • ATOMIC STRUCTURE
     • Atomic mass = protons + neutrons
     • no. of neutrons = atomic mass - atomic number
   • NUCLEAR DECAY
     • ALPHA = 4 2
     • BETA = 0 -1
   • OBSERVING RADIOACTIVE MATERIAL
     • work = F x d

3. ATOMIC STRUCTURE

   • Electrons - negatively charged, relative charge of 1 (tiny mass)
     • Protons - positively charged, relative charge is also 1 (tiny mass)
       • Neutrons - neutral, no overall charge, relative mass of +1
   • nucleus makes up 1/10,000 of the whole atom
     • one atom is roughly (~) 1x10^-10 m
   • an atom has a balanced number of protons and electrons, resulting in a neutral overall charge.
   • If an electron is lost or gained, the atom will become positively or negatively charged. It is now called an ION. This process is called IONISATION

4. OBSERVING RADIOACTIVE MATERIAL

   • BACKGROUND RADIATION
     • Low level radiation from radioactive sources in our environment
       • Artificial sources (man made) : 1- Medical 2- Nuclear weapons
       • Natural Sources: 1- Air (radon) 2- Ground/Cosmic rays
       • Safety Rules for handling RADIOACTIVE MATERIAL: 1- NEVER hold radioactive material directly. Use tweezers or tongs to avoid contamination. 2- NEVER point a source at anyone to reduce exposure. 3- Store any radioactive material in a lead-lined box when not in use to reduce exposure.

5. NUCLEAR RADIATION

   • Activity = the number of counts per second from a source of radiation in BEQUEREL (Bq)
   • TYPES OF RADIATION
     • ALPHA - made up of 2 protons and 2 neutrons. Relative charge of +2. Relative mass of 4. Attracted to negative plate due to its positive charge. Deflection is small due to its large mass. Very strongly ionising. Can penetrate through a few cm of air (paper)
     • BETA - made up of a high speed electron. Relative charge of -1. Relative mass of 1/2000 (0). Attracted to positive plate due to its negative charge. Deflection is large due to its small mass. Quite strongly ionising. Can penetrate through a few metres of air (Aluminium)
     • GAMMA - made up of a EM wave. Relative mass of 0. Relative charge of 0. Not attracted to anything as it has no charge. No deflection. Very weakly ionising. Can penetrate a few hundred metres (thick lead)

6. HALF LIFE

   • Decay - When a radioactive nucleus emits radiation (alpha,beta or gamma)
   • Radioactive Sample - An amount of radioactive material containing one type of radioactive atom

7. NUCLEAR FISSION

   • NOT alpha,beta or gamma. These are spontaneous reactions that happen without any intervention.
   • FISSION is a stimulated nuclear reaction. Spontaneous fissions are very rare.
   • e.g The Uranium nucleus absorbs a neutron. It becomes Uranium 236, which is very unstable.
     • This nucleus splits into pieces.
       • The result of the fission is always two daughter nuclei or 2/3 neutrons

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