Science Term 2 Notes

• Explain what a polymer is and why it is important in society.


  Polymer is a long molecule made up out of repeating monomers. Uses: credit cards, toys, pipes, shower curtains, car tires, clothing, pillow stuffing and plastic
• What are the 7 diatomic elements

  Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine
• Define reaction rate


  the quantity of reactant or product used up or made per unit time; how fast the reaction goes
• Explain the difference between a large reaction rate and a small reaction rate

  Large Reaction Rate: Fast conversion of reactants to products

  Small Reaction Rate: Slow conversion of reactants to products
• Explain the three requirements for a successful collision

  Correct orientation, sufficient energy, collision
• Formula of Reaction Rate

  Reactionrate = quantity ofreactant used up/ time

  OR

  reaction rate = quantity of product formed/time
• Which of is an example of a biofuel?

  Ethanol
• Which gas is produced during the fermentation of glucose?

  Carbon Dioxide
• Why is the majority of iron extracted used to make steel?

  Steel is less brittle and softer than iron.
• Which three elements are in CFCs?

  chlorine, carbon and fluorine
• A horizontal line on a volume versus time graph means that the rate

  of reaction is zero
• Explain what happens to an ethene monomer in a polymerisation reaction to form polyethene

  When the ethene molecules join together, the double bond is broken and the carbon atoms instead share an electron with the ethene molecule to either side
• What is synthesis, decomposition, precipitation and combustion?

  Synthesis: 2 chemicals become 1

  Decomposition: 1 becomes 2

  Combustion: Oxygen on one side, water and CO2 on the other

  Precipitation: process of forming an insoluble compound either by reacting two salts or by changing the temperature to affect the solubility of the compound
• Explain why coating iron with zinc protects it from rusting.


  Coating iron with zinc prevents rusting of the iron because zinc is more reactive than iron. This means that it preferentially reacts with oxygen or water, forming zinc oxide. This layer of zinc oxide forms over the iron underneath and protects it from corrosion.
• A substance that can supply or take the place of oxygen in a chemical reaction is known as


  oxidant
• The greatest concentration of the ozone layer is at an altitude of

  30 km
• What is the difference between thermal decomposition and electrolytic decomposition?

  Thermal decompositions use heat to provide energy for this reaction. Electrolytic decompositions use electricity to provide energy for this reaction
• Elements


  A species of atoms that have the same number of protons
• Electron Shell


  Houses the electrons which orbits the nucleus of an atom
• Electronic Figuration


  The arrangement of an atom's electrons in the shells around the nucleus
• Ground State


  Lowest energy level of an atom
• Valence Electrons


  Electrons on the outer shell of an element
• Ions


  A charge version of an atom, formed from the loss or gain of electrons
• Cations


  Positively charged ion formed from the loss of electrons
• Anions


  Negatively charged ions from the gain of electrons
• Ionic Bonding


  A strong bond between an anion and a cation, formed via electron donation
• Covalent Bond


  A strong bond almost always between two non metals who share electrons, forming a molecule
• Electron Shell Capacity


  First shell can only house 2, second holds up to 8, third holds max 18, 4 up to 32
• When electrons fill shells, they start with the lowest energy (shell closest to the nucleus)
• Though some shells can hold a lot of electrons, elements consider 8 electrons in a shell stable enough, so the excess electrons are housed in the next shell
• Biggest influence on an element's chemical and physical properties


  The number of electrons in the outermost shell
• Valence electrons are most affected when bumping into another atom
• Elements with the same number of valence electrons are grouped together
• All elements in group 1 have one valence electron
• The last digit of group 17 tells us that elements in this group have seven valence electrons
• This handy trick works for all the elements up to calcium (Ca)
• Electron Energy Levels


  When electrons gain energy, it can cause them to have higher energy levels such as jumping to the next electron shell, when electrons go back to ground state, energy is lost as light energy
• Metals


  Tend to lose electrons rather than gain as it is more easier, forming positively charged ions called cations
• Cations


  Elements that lose electrons become positive
• Anions


  Non mental gain electrons for a complete outer shell, forming negatively charged ions