temperature changes in reacting solutions

• What is the purpose of the investigation described?

  To investigate temperature changes in reacting solutions
• What apparatus is used in the investigation?

  • Polystyrene cup
  • Thermometer
  • 250 cm³ glass beaker
  • Measuring cylinder
  • Top pan balance
• What types of chemical reactions can be investigated?

  Acids with metals, carbonates, and alkalis
• What is the method for reacting two solutions?

  1. Place polystyrene cup in beaker
  2. Measure 25 cm³ of each liquid
  3. Record temperature of one liquid
  4. Add second solution and record temperature change
  5. Change independent variable and repeat
• What is the first step in the method for reacting two solutions?

  Place the polystyrene cup inside the glass beaker
• What should be recorded after adding the second solution?

  The highest or lowest temperature obtained
• What could be changed as the independent variable in the first method?

  The concentration of one reactant
• What is the method for reacting a solid with a solution?

  1. Place polystyrene cup in beaker
  2. Measure 25 cm³ of solution
  3. Measure mass of solid or select metal piece
  4. Record temperature of solution
  5. Add solid and record temperature change
  6. Change independent variable and repeat
• What is the first step in the method for reacting a solid with a solution?

  Place the polystyrene cup inside the glass beaker
• What should be recorded after adding the solid?

  The highest or lowest temperature obtained
• What could be changed as the independent variable in the second method?

  The surface area of the solid
• What does a bigger temperature change indicate in a reaction?

  • More energy is absorbed or released
  • Endothermic reactions absorb energy
  • Exothermic reactions release heat
• What is the biggest source of error in the experiment?

  Unwanted heat transfer
• How can unwanted heat transfer be reduced?

  By using a lid
• What are the hazards associated with dilute acids and alkalis?

  • May irritate skin or eyes
  • Avoid contact with skin
  • Wear eye protection
• What should be done if dilute acids or alkalis contact the skin?

  Rinse off skin if necessary
• What are the hazards of solutions of metal salts?

  • Dangerous to the environment
  • Dispose as advised by teacher
  • Some collected for safe disposal
• How should metal salt solutions be disposed of?

  As advised by the teacher
• What does an energy level diagram indicate about a reaction?

  Whether it is exothermic or endothermic
• What does an energy level diagram show about reactants and products?

  The energy in the reactants and products
• What happens to energy in an exothermic reaction?

  Energy is given out to the surroundings
• How is energy change represented in an exothermic reaction?

  By a downwards arrow
• What occurs to energy in an endothermic reaction?

  Energy is taken in from the surroundings
• How is energy change represented in an endothermic reaction?

  By an upwards arrow
• What does a reaction profile include that is crucial for reactions?

  The activation energy
• Why is a reaction profile more useful than an energy level diagram?

  It describes how energy changes during the reaction
• What is activation energy?

  The minimum energy needed for a reaction
• How is activation energy represented in a reaction profile?

  As a 'hump' in the line
• Where does the activation energy start in a reaction profile?

  At the energy of the reactants
• What does the overall change in energy in a reaction represent?

  The difference between reactants and products' energy
• What is the energy change in exothermic reactions?

  The energy level decreases
• What happens to energy when bonds are broken or formed?

  Energy is transferred
• What type of process occurs when bonds are broken?

  Endothermic process
• What type of process occurs when bonds are formed?

  Exothermic process
• What happens to heat energy during an endothermic process?

  Heat energy is taken in
• What happens to heat energy during an exothermic process?

  Heat energy is given out
• What occurs to bonds during a chemical reaction?

  Bonds in reactants are broken and new bonds are made
• What determines the type of reaction in a chemical process?

  The difference in energy between breaking and making bonds
• When is a reaction considered exothermic?

  If more heat energy is released than taken in
• When is a reaction considered endothermic?

  If less heat energy is released than taken in