Unit 8

• What do the terms exothermic and endothermic refer to in chemical reactions?


  Exothermic reactions release energy, while endothermic reactions absorb energy.
• What is an example of an exothermic reaction?


  Combustion.
• What is an example of an endothermic reaction?


  Thermal decomposition.
• What happens in a combustion reaction?


  A fuel and oxygen are combined to produce carbon dioxide and water.
• How do self-heating food cans work?


  They transfer heat energy to the food to keep it hot.
• What must happen to water in order to make ice cubes?


  Water must be cooled, taking energy away from it.
• What are the indicators of whether a reaction is exothermic or endothermic based on temperature changes?


  • Exothermic: Temperature increases.
  • Endothermic: Temperature decreases.
• What does a temperature change indicate in a chemical reaction?


  It indicates whether the reaction is exothermic or endothermic.
• What are the examples of reactions categorized as exothermic or endothermic in the study material?


  Exothermic:

  • Combustion
  • Neutralisation
  • Self-heating food can

  
  

  Endothermic:

  • Sports injury pack
• What is formed when a metal reacts with oxygen?


  A metal oxide
• What do state symbols indicate in a chemical equation?


  They indicate whether a substance is a solid (s), liquid (l), gas (g), or aqueous (aq)
• How would you balance the equation for the reaction of copper with oxygen?

  __Cu + O$_2$ → __CuO
• What is the balanced equation for zinc reacting with oxygen?

  __Zn + O$_2$ → __ZnO
• What is the balanced equation for sodium reacting with oxygen?

  __Na + O$_2$ → __NaO
• What is the balanced equation for magnesium reacting with oxygen?

  __Mg + O$_2$ → __MgO
• What are the metals listed in order of most to least reactive?

  • Potassium
  • Sodium
  • Calcium
  • Magnesium
  • Aluminum
  • Zinc
  • Iron
  • Copper
  • Silver
  • Gold
• Which metals do not react with oxygen?


  Gold and platinum
• What are three uses of unreactive metals and their explanations?


  • Jewelry: Durable and resistant to tarnishing
  • Electronics: Conductive and corrosion-resistant
  • Medical devices: Biocompatible and non-reactive with body fluids
• Which alkali metals are mentioned in the study material?

  Lithium, Sodium, Potassium
• What prediction can you make about the reaction of rubidium with water?


  It will react vigorously with water
• What about the reactions of Caesium and Francium with water?


  They will also react vigorously with water
• What are the products of the reaction between potassium and water?


  • Potassium hydroxide
  • Hydrogen gas
• Complete the equation: Lithium + Water → ______ + Hydrogen.


  Lithium hydroxide
• Complete the equation: Sodium + Water → ______ + ______.


  Sodium hydroxide + Hydrogen
• Complete the equation: Rubidium + Water → ______ + ______.


  Rubidium hydroxide + Hydrogen
• What is the prediction about metals when placed in acid?


  Gas is made
• What are the three important acids for studies?

  • Hydrochloric acid (HCl)
  • Sulfuric acid (H₂SO₄)
  • Nitric acid (HNO₃)
• What is the general reaction formula for a metal reacting with an acid?


  Metal + acid → salt + hydrogen
• What happens to the name of the acid when it forms a salt?

  The name 'chloric' becomes 'chloride'
• What is produced when magnesium reacts with hydrochloric acid?


  Magnesium chloride and hydrogen
• How can you test for hydrogen gas produced in a reaction?


  By performing the squeaky pop test
• What are the steps in the experiment to observe the reaction of magnesium with acid?


  1. Add acid to the test tube
  2. Measure the temperature
  3. Add magnesium strip and observe
  4. Measure the temperature during the reaction
• What is the observation when magnesium reacts with acid?


  It produces bubbles and heat
• What are the names of the salts produced from the following acids?

  • Hydrochloric acid → Chloride
  • Sulfuric acid → Sulfate
  • Nitric acid → Nitrate
• What is the product of the reaction between hydrochloric acid and iron?


  Iron chloride
• How do different metals react with acids?


  They react at different rates
• What is the difference in reactivity between sodium and copper when placed in acid?


  Sodium reacts vigorously, while copper does not react
• What is the temperature change observed during the reaction of magnesium with hydrochloric acid?


  The temperature increases
• What is the equation for the reaction of magnesium with hydrochloric acid?

  Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen
• What is the significance of the suffixes -ide and -ate in the names of salts?


  • ide is used for chlorides, while -ate is used for sulfates and nitrates