Term 1

• Physical change:  type of change where the physical properties of matter change and can be reversible.
• Chemical change: a change that causes a new substance to be formed and is irreversible.
• Identify whether the changes are physical or chemical:

  melting ice: physical

  burning a match: chemical

  Heating copper metal: chemical
• The appearance of sodium chloride (salt) before heating, during heating and after heating?

  Before heating: white solid

  during heating: white solid

  after heating: white solid
• The appearance of Ammonium chloride before heating, during heating and after heating?

  Before heating: white solid

  During heating: sublimes to form a white gas

  After heating: condenses to a white solid
• The appearance of Zinc oxide before heating, during heating and after heating?

  before heating: white solid

  during heating: turns into a yellow solid

  after heating: white solid
• Method for heating chemicals:

  Heat each chemical gently at first and then more strongly until it undergoes a change. Once it has changed, stop heating and observe.
• Apparatus for heating chemicals: 


  Diagram of apparatus for heating chemicals:

  
• What colour is the zinc oxide when you heat it?

  Yellow
• How does the wax change when you heat it?

  Melts to form a colourless liquid.
•  Melting = physical change.
• To Investigate the Effect of Heat on Copper(II) Carbonate

  Method:

  1.  Place an empty beaker on the balance. 

  2. Press tare to zero the balance. 

  3. Put an empty dry test tube into the beaker. Record its mass in the table below as (Mass 1) .

  4. Put 2-3 spatulas full of Copper(II) Carbonate into the dry test tube and re-weigh it, record this mass in the table (Mass 2).

  5. Heat the test tube with the Copper(II) Carbonate in the strong Bunsen flame until no more change can be seen.

  6. Allow the tube to cool down and then weigh it again (Mass 3) and record the mass in the table.
• Copper (II) Carbonate before heating: GREEN

  New solid after heating: BLACK
• 1. What has happened to the mass of the copper(II) carbonate?

  Decreased
• What has happened to the mass of the copper(II) carbonate when heated?

  Decreased
• Why is the mass of copper(II) carbonate decreasing after heating?

  Losing a colourless gas to the atmosphere.
• Carry out the following simple experiment to discover why the mass of copper 2 carbonate changes during heating:

  • Take two empty dry test tubes. 
  • In the first place some copper(II) carbonate.
  • In the second place some limewater, connect the two test tubes with a delivery tube.
  • Heat the copper (II) carbonate gently in the blue flame. Record your observations.
• The apparatus for discovering why the mass of copper(II) carbonate decreases after heating.

  
•  Thermal decomposition is a chemical reaction. That happens when a compound breaks down when heated. 
• copper(II) carbonate decreases in mass because it goes through thermal decomposition.

  Copper(II) Carbonate 🡪 copper(II) oxide + carbon dioxide
• Why does the mass of copper(II)carbonate decrease during heating?

  It loses a colourless gas to the atmosphere.
• Which gas is made during the reaction of copper(II) carbonate and how is it identified?

  Carbon dioxide, which turns limewater milky white
• What is the chemical left in the test tube after heating copper (ll) carbonate?

  Copper(II) oxide
• The word equation for heating copper (ll) carbonate:

  Copper(II) Carbonate 🡪 copper(II) oxide    +    carbon dioxide                                           
• Method for heating copper (ll) sulphate:

  1.  Place an empty beaker on the balance. 

  2. Press tare to zero the balance. 

  (Follow this procedure for every weighing that you do in this experiment, taking care to use the same beaker). 

  3. Put an empty dry test tube into the beaker. Record its mass in the table below (Mass 1).

  4. Put 2-3 spatulas full of Copper(II) Sulphate into the dry test tube and re-weigh it. Record this mass in the table (Mass 2).

  5. Heat the test tube with the Copper(II) Sulphate in the strong Bunsen flame until no more change can be seen.
• Copper (II) Sulphate before heating: Blue crystalline solid

  Copper (II) Sulphate after heating : Grey/white powdery solid
• Describe what you see happening as the Copper (II) Sulphate crystals are heated.

  • Blue crystals change to a greyish white powder.
  • A colourless liquid condenses on the cooler parts of the tube.
  • Steam comes out of the mouth of the tube.
• What is being lost by the crystals of Copper (II) Sulphate?

  A colourless liquid (water)
• What do we call crystals that contain water?

  Hydrated
• What do we call the solid after the water has been lost by the crystals?

  Anhydrous
• Hydrated copper(II) sulphate ⇋ Anhydrous copper(II) sulphate + water
• ⇋  means that the process is REVERSIBLE
• Is the action of heat on Hydrated Copper(II) Sulphate a physical or chemical change? Explain your answer –

  Chemical change in which new chemicals are made.
• Give one piece of evidence that suggest that water is given out when Hydrated Copper(II) Sulphate is heated

  A colourless gas is given off, which condenses to a colourless liquid on the cooler parts of the tube.
• Diagram of investigating the effect of heat on magnesium metal


  Diagram:

  
• Method for investigating the effect of heat on magnesium metal

  1.Weigh a nickel crucible with its lid on to get Mass 1.

  2. Coil a 10 cm length of magnesium ribbon into the crucible, replace the lid, and weigh again to get Mass 2.

  3. Heat the crucible with magnesium inside on a Bunsen burner. Remove the lid initially, and when the magnesium starts changing, hold the lid about 1cm above the crucible.

  4. When the reaction is complete, stop heating, replace the lid, and let it cool for several minutes.

  5. Re-weigh the crucible to get Mass 3.
• Appearance of the magnesium at start: Silvery grey solid

  Appearance of the final product (the solid at the end of the experiment): White powdery solid
• What happens to the mass of the magnesium?

  It increases
• What is the name of the solid formed in the investigation of the effect of heat on magnesium metal?

  Magnesium oxide
• What is the word equation for magnesium oxide?

  
  

  Magnesium + Oxygen 🡪 Magnesium oxide