Science

• Comet - made of ice, rocks and dust.
• Meteoroid - space rocks and debris in the solar system.
• Asteroid - refes to small celestial bodies compose of rocks and metals.
• Nucleus - solid part and stable part of a comet that compose of gas, dust and ice.
• Crater - an evidence of the impact of space rocks that hit the earth.
• asteroidos are small, rocky objects like the orbut the sun although asteroids orbut the sun they are much smaller than planets.
• coma - dense cloud of water , carbon dioxide and other neutral gases sublimated from the nucleus.
• in japan the supertions that are related to asteroid is that is death calling therfore people are scared to see the comets and asteroids.
• Pure substance


  Form of matter that have the same definite and unchanging chemical composition that can be classified as elements or compound
• Elements


  • Substance that are made up of only one type of atom
  • They can be broken down into simpler substance by ordinary chemical means
• Oxygen is the most abundant element in the earth's crust, followed by Silicon. It is also the major component of the human body, followed by Carbon
• Important elements in the human body

  • p.187 table 9.2
• Radioactive element


  An example is Cobalt-60, used in gamma radiation to treat cancer
• Foods may be irradiated, using gamma rays from cobalt-60 or cesium-137, to retard the growth of organisms such as bacteria, molds and yeast. It prolongs the shelf life under refrigeration in the same way that heat pasteurization protects milk. FDA has approved irradiation of many classes of food
• Compound


  Substance that are made up of more than one type of atom. These can be separated into two or more simpler substance by ordinary chemical reaction
• Compounds


  • Water- hydrogen and oxygen
  • Salt- sodium and chloride
  • Carbon dioxide- carbon and oxygen
• The properties of compounds are very different from the properties of the elements of which it is composed
• Properties of elements


  • Chlorine- a very poisonous green gas with intensely disagreeable suffocating odor
  • Sodium- a soft metal that can be cut easily with the table knife, it reacts violently in water
• These properties are very different from sodium chloride, being a colorless or white crystalline compound that can be used as a food preservative or seasoning
• Mixture


  Made up of two or more substances that are physically combined
• Mixtures


  • soil
  • Blood
  • Seawater
  • Air
  • Milk
  • Rocks
• Homogeneous mixture


  Have only one phase, or have uniform appearance throughout any portions
• Solution


  A homogeneous mixture of two or more substances in variable composition
• Solutions


  • Salt and water
  • Rubbing alcohol
• Solute


  The substance that gets dissolved
• Solvent


  The substance that does the dissolving
• Water is a universal solvent
• Physical separation methods


  • Filtration
  • Evaporation
  • Sublimation
  • Distillation
  • Decantation
  • Crystallization and use of sieves and magnet
• Chemical separation methods include heating using electricity or light energy
• Heterogeneous mixture


  Made up of more than one phase or of different parts and can be separated by physical means
• The different components of a heterogeneous mixture are visibly distinguishable from one another
• Potential difference


  The amount of energy needed to move a charge of 1 C (coulombs) from one point to another. This energy is usually referred to as voltage in an electric circuit.
• Volt


  The unit of potential difference, represented by a capital letter V.
• Italian physicist Alessandro Volta invented the first electric cell


  1799
• Voltaic pile


  • Consisted of alternating discs made of zinc and silver, with a piece of cloth soaked in salt solution between them
  • Formed the basis of modern cells and batteries such as the dry cell, storage battery, and nickel-cadmium cell
• Primary cells


  Cells that cannot be recharged
• Secondary cells


  Cells that are rechargeable
• Primary and secondary cells

  • Dry cell (primary)
  • Storage battery (secondary)
  • Nickel-cadmium cell (secondary)
• Connecting cells in series

  The total voltage is the sum of the individual voltages
• Connecting cells in parallel


  The total voltage is equal to the voltage of one cell