year 9 chemistry introductory unit

• what’s an atom


  the smallest part of an element
• what’s an element 


  only one type of atom
• what’s a molecule 


  two or more atoms chemically joined together
• define a pure substance 


  a substance that only contains only one type of element or compound
• define mixture


  a collection of elements or compounds that are not chemically joined
• define formulation


  a formulation is a mixture that has been designed for a useful product
• define distillation


  a method of separating substances based on their boiling point
• define chromatography 


  the process where dissolved substances are separated from each other
• the more soluble a substance is the higher…


  up the stationary phase it travels
• how do you calculate Rf value


  Rf=distance travelled by substance divided by the distance travelled by solvent
• What are atoms?

  Tiny particles that make up all matter
• How are atoms of each element represented?

  By a chemical symbol
• What is the chemical symbol for oxygen?

  O
• What is the chemical symbol for calcium?

  Ca
• What is the rule for writing a chemical symbol with one letter?

  The letter must be capital
• What is the rule for writing a chemical symbol with two letters?

  The first letter must be capital and the second must be lowercase
• What defines an element?

  A substance made up of only one type of atom
• What are compounds?

  Substances containing two or more elements chemically combined in fixed proportions
• How can compounds be separated?

  Only by chemical reactions
• What are the rules for naming compounds?

  • Name of the metal goes first
  • Name of the non-metal goes second
  • Change the non-metal name ending from -ine to -ide
• What is a pure substance?

  A substance made up of just one type of element or compound
• What is a mixture?

  A combination of two or more different elements or compounds that are not chemically joined
• What is a formulation?

  A mixture specifically designed to produce a useful product
• How can melting and boiling points be used to identify pure substances?

  Pure substances have a very small range of melting and boiling points
• What happens to the boiling point of an impure substance?

  It generally has a higher boiling point than the pure substance
• What are the methods used to separate mixtures?

  • Filtration: separates insoluble solids from liquids
  • Evaporation: separates soluble solids from liquids
  • Distillation: separates mixtures of liquids based on boiling points
• What is chromatography used for?

  To separate a mixture of substances that can be dissolved in the same solvent
• What is the stationary phase in paper chromatography?

  The paper
• What is the mobile phase in paper chromatography?

  The solvent that carries the sample up the paper
• How do different compounds travel in chromatography?

  They travel different distances depending on solubility and attraction to the stationary phase
• What is the formula for calculating the R_f value?

  R_f = Distance moved by substance / Distance moved by solvent
• What does the R_f value indicate?

  It helps identify unknown compounds by comparing with known values
• Why is the baseline drawn in pencil in chromatography?

  To prevent the ink from traveling up the paper and obscuring results
• What happens if the pencil baseline is submerged in the solvent?

  The sample spots will dissolve into the beaker and be lost
• What is the positive test for hydrogen gas?

  It burns rapidly with a squeaky pop sound
• What is the positive test for oxygen gas?

  A glowing splint will relight
• What is the positive test for chlorine gas?

  It bleaches damp blue litmus paper white
• How can chromatography be used to identify unknown compounds?

  By comparing the distance traveled by the unknown with known compounds