Energy Change

• What is meant by an exothermic reaction?

  An exothermic reaction is one that transfers energy from the reacting molecules to the surroundings.
• How does an exothermic reaction affect the temperature of its surroundings?

  The temperature of the surroundings increases, making them hotter.
• What is a common example of an exothermic reaction?

  Combustion, such as wood burning, is a common example of an exothermic reaction.
• What are two other examples of exothermic reactions?

  Certain oxidation reactions and neutralization reactions are examples of exothermic reactions.
• What is an energy profile diagram?

  • A diagram that represents the energy changes during a chemical reaction.
  • Shows the energy of reactants, products, and the activation energy.
• In an exothermic reaction energy profile, how do the energy levels of products compare to reactants?

  The products have less energy than the reactants because energy has been transferred to the surroundings.
• What does the difference in energy between reactants and products in an exothermic reaction indicate?

  It indicates the amount of energy that has been released to the surroundings.
• What are two practical applications of exothermic reactions?

  Exothermic reactions are used in hand-warmers and self-heating cans.
• What is meant by an endothermic reaction?

  An endothermic reaction takes in energy from its surroundings.
• How does an endothermic reaction affect the temperature of its surroundings?

  The temperature of the surroundings decreases, making them colder.
• What is a good example of an endothermic reaction?

  Thermal decomposition is a good example of an endothermic reaction.
• In an endothermic reaction energy profile, how do the energy levels of products compare to reactants?

  The products have more energy than the reactants because energy has been taken in from the surroundings.
• What does the difference in energy between reactants and products in an endothermic reaction indicate?

  It indicates the amount of energy that has been taken in by the reaction.
• What is the activation energy in a chemical reaction?

  • The minimum amount of energy that particles must have in order to react.
  • Reactions can only occur when particles collide with sufficient energy.
• How is activation energy represented on an energy profile diagram?

  Activation energy is represented as the energy from the reactants to the peak of the curve.
• How do the energy profiles of exothermic and endothermic reactions compare?

  Both have a peak representing activation energy, but exothermic reactions release energy while endothermic reactions absorb energy.
• What should you be able to describe by the end of the video on temperature changes in chemical reactions?

  How to investigate the variables that affect temperature changes in chemical reactions
• What types of reactions are mentioned in the study material?

  Exothermic and endothermic reactions
• What is the specific reaction being investigated in this practical?

  The neutralization reaction between hydrochloric acid and sodium hydroxide
• What is the independent variable in this experiment?

  The volume of sodium hydroxide solution
• What is the dependent variable in this experiment?

  The maximum temperature reached
• What are the control variables in this experiment?

  The volume of hydrochloric acid and the concentrations of both solutions
• What is the first step in the practical procedure?

  Measure 30 centimeters cubed of dilute hydrochloric acid
• Why do we place the polystyrene cup inside a beaker?


  To prevent the cup from falling over
• What should be done after transferring hydrochloric acid to the polystyrene cup?

  Measure the temperature of the acid and record it
• What happens to the temperature of the solution during the exothermic reaction?

  The temperature of the solution increases
• What should you do when the thermometer reading stops changing?

  Record the highest temperature reached
• How is the experiment repeated with different volumes of sodium hydroxide solution?

  By using 10 centimeters cubed of sodium hydroxide solution and increasing by 5 centimeters cubed each time
• What trend is observed when increasing the volume of sodium hydroxide solution?

  The maximum temperature reached increases initially
• Why does the maximum temperature start to decrease after a certain volume of sodium hydroxide solution?

  There is not enough hydrochloric acid to react with all the sodium hydroxide
• What happens to the energy released when large volumes of sodium hydroxide are added?

  The energy released is spread out into a greater volume
• Why is a polystyrene cup with a lid used in this experiment?

  To reduce heat losses during the temperature measurement
• What property of polystyrene makes it suitable for this experiment?


  It is a good thermal insulator
• What type of questions can be found in the vision workbook related to this practical?


  Questions related to the required practical
• What are the steps involved in the practical investigation of temperature changes in an exothermic reaction?

  1. Measure 30 cm³ of dilute hydrochloric acid.
  2. Transfer acid to a polystyrene cup.
  3. Measure initial temperature and record it.
  4. Add 5 cm³ of sodium hydroxide solution.
  5. Fit a lid and insert thermometer.
  6. Stir gently and observe temperature rise.
  7. Record the highest temperature reached.
  8. Repeat with increasing volumes of sodium hydroxide.
  9. Calculate mean values and plot a graph.
• What are the key observations regarding the relationship between sodium hydroxide volume and maximum temperature reached?

  • Maximum temperature increases with more sodium hydroxide.
  • After a certain volume, maximum temperature decreases.
  • Energy released is spread over a larger volume of solution.
• What should you be able to describe by the end of the video on batteries?

  What is meant by a cell and battery, evaluate the use of different metals in batteries, and describe the differences between rechargeable and non-rechargeable batteries.
• What is an electrolyte?


  An electrolyte is a solution that can conduct electricity, such as a solution of an ionic compound.
• If you connect a strip of copper and a strip of magnesium in an electrolyte, what will happen?

  A potential difference will be observed, and an electric current will flow through the wire.
• What is a cell in the context of batteries?

  A cell is a setup that generates electricity through a chemical reaction between two different metals in an electrolyte.