space and radioactivity

• Atoms are composed of a central nucleus and an electron cloud.There are three particles in an atom; protons, neutrons and electrons.

  
• Why are some atoms radioactive


  Some atoms have an unstable nucleus. All nucleii want to be stable. To become stable the nucleii emit radiation in the form of particles or a high energy electromagnetic wave. When the nucleus emits radioacivity we say it decays.The unstable nucleus is now more stable.Frequently very large nucleii (e.g. uranium atoms) are unstable and need to decay to become stable.
• three types of radioactivity: Alpha Beta Gamma
• Alpha Radiation 

  is composed of two protons and two neutrons.It is the same as a helium nucleus.It is a PARTICLE.
• Beta Radiation

  A beta particle is composed of a high energy electron.It is a PARTICLE.
• Gamma Radiation

  Gamma radiation is an electromagnetic wave. It is part of the electromagnetic spectrum.  It is NOT A PARTICLE.
• Stopping Alpha, Beta and Gamma Radiation

  Alpha: Stopped by a few centimetres of air, paper & skin. Beta: Can pass through skin but is stopped by a thin sheet of aluminium (or several metres of air). Gamma: Only stopped by thick concrete or lead.
• Measuring Radioactivity

  A Geiger-Muller Tube is used to detect and to count the amount of radioactivity produced by an object or in a location. It has a display to show the number of 'counts per minute' - the number of times a radiocative particle or wave comes in contact with the tube every minute.
• What is Background Radioactivity?

  This is radioactivity that is around us at all times. In most places background radioactivity is at low levels that will not harm human health.There are two types of Background Radioactivity;-Natural and Man-Made
• Examples of Natural Background Radiation

  • Cosmic Rays (from space)
  • Food and Drink
  • Radioactive Rocks
  • Radon Gas in some areas
• Examples of Man-Made Background Radiation

  Nuclear Power-stations

  Nuclear bomb testing

  Medical Uses e.g. to treat cancer, X-Rays
• uses of radioactivity

  To sterilize medical equipment.

  (Sterilize means to kill bacteria and viruses on the surface of the equipment).

  It is important that Medical Equipment (scissors, scalpels, gloves, syringes etc.) is sterile. This prevents patients picking up infections.To sterilize the equipment it is first sealed in an airtight package and passed through a beam of gamma radiation. The gamma rays kill all bacteria and viruses. Because the equipment is in an airtight package no new bacteria or viruses can contaminate the equipment - and remain sterile.
• uses of radioactivity

  To extend the shelf life of soft fruitsSoft fruits like strawberries and raspberries decay quickly (they have a short shelf life). Bacteria and fungi living on the surface make them decompose.Soft fruits can be treated with gamma radiation to kill the bacteria and fungi. The fruits will last longer and not decay as quickly. This is safe and doesn't effect the taste of the fruit.
• uses of radioactivity

  To control the thickness of materials (e.g. paper, card or metal foil).Beta radiation is used (it can pass through paper and thin metal foil).The material is too thick.Less beta particles pass through the material. The reading on the detector is too low. The rollers move closer together. More pressure is applied. This produces a thinner sheet of material.The material is too thin.Lots beta particles pass through the material. The reading on the detector is too high. The rollers move further apart. Less pressure is applied. This produces a thicker sheet of material.
• solar system

  mercury - venus - earth - mars - juptier - saturn - uranus - neptune ( pluto)
• Solar System is made up of : The Sun is at the centre of the Solar System. It is a star because it produces its own light and heat. Eight Planets (a plant is a body that orbits a star - our Sun) Many Moons - Earth has one moon. The Asteroid Belt - an area of rocks and boulders - this is located between Mars and Jupiter (some scientists think it is a planet that never formed). Sometimes an asteroid can break free from the asteroid belt. Comets - that are large lumps of rock and ice that orbit The Sun. They produce a long tail as they get closer to The Sun.
• The four inner planets (closest to the Sun) are made from rock. They are called the Rocky Planets. The four outer planets are made from gas and are much larger. They are called the Gas Giants
• Satellites

  A satellite is a body that orbits another body.Examples:The Earth orbits The Sun. The Earth is a satellite of The Sun.The Moon orbits the Earth. The Moon is a satellite of The Earth.There are two types of satellite; Natural and Artificial (Man-Made)
• Natural SatellitesMoons, planets, comets and asteroids are natural objects. They are all natural satellites.e.g. A comet orbits The Sun. A comet is a natural Satellite.
• Artificial (Man-Made) Satellites

  The International Space Station is the largest artificial satellite orbiting The Earth.

  Artificial Satellites are also used for;

  Forecasting the Weather

  Communication (SKY TV satellite or moble phone satellites)

  Sat-Nav for cars

  GPS for mobile phones

  Taking photographs of the Earth's surface (e.g. Google Earth)
• The Difference between Mass and Weight

  the mass and weight of an object are very different things.The mass of an object is the amount of matter in an object.Weight is the pull of gravity on an object. A bag of sugar has a mass of 1 kilogram. The mass will remain at 1 kg, no matter where we take it to in the Solar System. It will have the same mass on Earth, the Moon, Jupiter, Mars etc. This is because it still has the same amount of sugar inside the bag -1 kg of sugar.
• Weight is force produced by the pull of gravity on the mass of an object. The larger the size of a body (Star, Planet or Moon) the more gravity it possesses, the greater the weight of the object.
• Calculating WeightWeight = Mass x Gravityw = m x g

  Weight = Newtons

  Mass = Kilograms

  Gravity on Earth = 10 m/s2
• Asteroid Srikes

  The surface of The Moon is covered in craters.

  A crater is produced when the surface is hit by an asteroid.

  Most asteroids are found in the asteroid belt however, they can occasionally break free and travel around the Solar System.

  The Earth has been struck by asteroids in the past.