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• What should you know after studying reaction profiles?

  How to draw reaction profiles and identify reactions
• What is activation energy?

  The minimum energy needed to start a reaction
• How can you identify a reaction as exothermic or endothermic using reaction profiles?

  By comparing energy levels of reactants and products
• What do reaction profiles show about energy changes during a reaction?

  They show energy levels of reactants and products
• What is the energy change during an exothermic reaction?

  Energy is transferred to the surroundings
• What happens to the temperature of surroundings during an exothermic reaction?

  The temperature of the surroundings rises
• What characterizes an endothermic reaction in terms of energy levels?

  Products are at a higher energy level than reactants
• What happens to the temperature of surroundings during an endothermic reaction?

  The temperature of the surroundings decreases
• What is the definition of activation energy?

  The minimum energy needed for a reaction
• What occurs when colliding particles have less energy than the activation energy?

  They bounce off each other without reacting
• What happens during bond breaking and bond making in a chemical reaction?

  • Bonds in reactants are broken first
  • Energy is supplied to break bonds (endothermic)
  • New bonds are formed to create products
  • Energy is released when new bonds form (exothermic)
• What is the energy change when bonds are broken?

  Energy is absorbed from the surroundings
• What is the energy change when bonds are formed?

  Energy is released to the surroundings
• How do you determine if a reaction is exothermic or endothermic?

  By comparing energy required to break and form bonds
• How can you investigate energy changes in chemical reactions?

  By measuring temperature changes in solutions
• What apparatus can be used to investigate temperature changes in reactions?

  A polystyrene cup and a thermometer
• What should you record during an investigation of temperature changes?

  The initial and maximum/minimum temperatures
• What could you consider to extend your investigation into energy changes?

  How quantities of reactants affect temperature change
• What are the key points regarding energy changes in reactions?

  • Energy cannot be created or destroyed
  • Energy is transferred to/from surroundings
  • Exothermic reactions release energy, raising temperature
  • Endothermic reactions absorb energy, lowering temperature
• What are the characteristics of exothermic and endothermic reactions?

  Exothermic:

  • Products have lower energy than reactants
  • Energy is released to surroundings

  
  

  Endothermic:

  • Products have higher energy than reactants
  • Energy is absorbed from surroundings
• What is the relationship between bond breaking and energy changes?

  • Breaking bonds requires energy (endothermic)
  • Forming bonds releases energy (exothermic)
• What is the energy change in endothermic reactions?

  Products have higher energy than reactants
• What is the energy transferred from the surroundings in the reaction CaCO₃(s) → CaO(s) + CO₂(g)?

  178 kJ/mol
• What apparatus can be used to investigate energy changes in reactions involving solutions?

  • Polystyrene cup
  • Thermometer
• How can you investigate temperature changes in reactions?

  Mix reactants and record temperature changes
• What should you consider when predicting temperature changes in reactions?

  Quantities of reactants used
• What is the purpose of the thermometer in the investigation?

  To measure temperature change during reaction
• How does the polystyrene cup help in the investigation?

  It insulates and reduces energy transfer rate
• What safety equipment should be worn during the investigation?

  Eye protection
• What happens when sherbet dissolves in water in your mouth?

  It takes in energy, providing a cooling effect
• What is conserved in chemical reactions?

  • Energy is conserved
  • It is neither created nor destroyed
• What is an exothermic reaction?

  Energy is transferred to surroundings
• What is an endothermic reaction?

  Energy is absorbed from surroundings
• What would you feel holding a beaker of water while dissolving potassium nitrate?

  It would feel colder due to energy absorption
• What can you deduce from a temperature change from 19°C to 27°C in a reaction?

  Energy was transferred from the mixture to surroundings
• What is the energy required for the thermal decomposition of 18.0g of magnesium carbonate?

  21.4 kJ
• How do you write a balanced symbol equation for magnesium carbonate decomposition?

  MgCO₃(s) → MgO(s) + CO₂(g)
• How do you calculate the number of moles of magnesium carbonate broken down?

  Use the formula: moles = mass / molar mass
• What is a use of exothermic reactions in hand warmers?

  To warm hands in cold conditions
• How do disposable hand warmers work?

  They use oxidation of iron to release heat