RoR & Energy Changes

• What is the core practical for investigating the effects of changing conditions on the rates of chemical reactions?

  Measuring the production of a gas and observing a colour change
• What reactions are investigated in the core practical?

  The reaction between hydrochloric acid and marble chips, and the reaction between sodium thiosulfate and hydrochloric acid
• How does changing the size of marble chips affect the rate of reaction?

  Smaller chips have a larger surface area, resulting in a faster rate of reaction
• How does changing the concentration of hydrochloric acid affect the rate of reaction?

  A greater concentration results in a greater number of particles in a given volume, leading to a faster rate
• What are the two methods for measuring the rate of a given reaction?

  • Measuring the amount of reactant used
  • Measuring the amount of product formed over time
• What is the formula for the rate of reaction based on the amount of reactant used?

  Rate of reaction = amount of reactant used / time
• What is the formula for the rate of reaction based on the amount of product formed?

  Rate of reaction = amount of product formed / time
• How can the quantity of reactant or product be measured?

  By mass in grams or by volume in cm³
• What are the units of the rate of reaction?

  g/s or cm³/s
• How can you measure the reactant used if the product is a gas?

  By carrying out the reaction on a set of weighing scales and measuring the mass lost
• How can you measure the product formed if the product is a gas?

  By measuring the volume of gas produced in a gas syringe
• What is required for chemical reactions to occur between particles?

  The reacting particles must collide with enough energy, known as activation energy
• How can the rate of a reaction be increased?

  By increasing the frequency or energy of collisions
• What factors can increase the rate of a reaction?

  • Increasing temperature
  • Increasing pressure
  • Increasing concentration
  • Increasing surface area
  • Using a catalyst
• How does increasing temperature affect the rate of reaction?

  It increases the kinetic energy of particles, leading to more frequent and energetic collisions
• How does increasing pressure affect the rate of reaction in gases?

  It increases the number of particles in a given volume, leading to more frequent collisions
• How does increasing concentration affect the rate of reaction in solutions?

  It increases the number of particles in a given volume, leading to more frequent collisions
• How does increasing the surface area of solid reactants affect the rate of reaction?

  It increases the frequency of collisions, leading to a faster rate of reaction
• How can the rate of reaction be determined graphically?

  • Draw tangents to curves on the graph
  • Use the slope of the tangent as a measure of the rate of reaction
• What does a steeper line on a rate of reaction graph indicate?

  A greater increase or decrease in the rate of reaction
• How should you interpret a graph showing a product?

  You would expect the mass/volume/concentration to increase
• How should you interpret a graph showing a reactant?

  You would expect the mass/volume/concentration to decrease

  
• What is a catalyst?

  A substance that speeds up the rate of a reaction without altering the products
• How do catalysts affect chemical reactions?

  They speed up reactions without being changed or used up

  
• How do catalysts increase the rate of a reaction in terms of activation energy?

  They decrease the activation energy, increasing the proportion of particles with energy to react

  
• How do catalysts lower activation energy?

  By providing a different pathway for a chemical reaction with lower activation energy

  
• What are enzymes?

  Biological catalysts
• What enzyme is used in the production of alcoholic drinks?

  Yeast
• How is ethanol produced in alcoholic drinks?

  It is fermented from sugars by yeast
• What changes in heat energy accompany the dissolution of salts in water?

  Salts dissolving in water can be either exothermic or endothermic.
• What type of reaction is a neutralisation reaction?

  A neutralisation reaction is exothermic.
• What type of reaction is a displacement reaction?

  A displacement reaction can be either exothermic or endothermic.
• What type of reaction is a precipitation reaction?

  A precipitation reaction is exothermic.
• How can temperature changes be measured during reactions in solution?

  Temperature changes can be measured using a thermometer in a polystyrene cup with a lid.
• What defines an exothermic change or reaction?

  An exothermic change is one in which heat energy is given out.

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

  The temperature of the surroundings increases during an exothermic reaction.

  
• What are some examples of exothermic reactions?

  Examples of exothermic reactions include combustion, many oxidation reactions, and neutralisation.

  
• What are everyday examples of exothermic reactions?

  Everyday examples include self-heating cans (e.g., for coffee) and hand warmers.
• What defines an endothermic change or reaction?

  An endothermic change is one in which heat energy is taken in.

  
• What happens to the temperature of the surroundings during an endothermic reaction?

  The temperature of the surroundings decreases during an endothermic reaction.