Rates of Reaction and Energy Changes

• What is the core practical investigating in section 7.1?

  Effects of changing conditions on reaction rates
• What gas is produced in the reaction between hydrochloric acid and marble chips?

  Carbon dioxide
• What color change is observed in the reaction between sodium thiosulfate and hydrochloric acid?

  From clear to cloudy
• How does the size of marble chips affect the rate of reaction?

  Smaller chips increase surface area, speeding up reaction
• How does the concentration of hydrochloric acid affect the rate of reaction?

  Greater concentration increases the reaction rate
• What methods can be used to determine the rate of a reaction?

  • Measure amount of product used
  • Measure amount of product formed over time
  • Use mass in grams or volume in cm³
• What is the formula for the rate of reaction based on reactant used?

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

  Rate = amount of product formed / time
• What are the units of rate of reaction?

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

  Use weighing scales to measure mass loss
• How can you measure product formed if the product is a gas?

  Measure the volume of gas produced
• What is required for a chemical reaction to occur?

  Reacting particles must collide with enough energy
• What is the minimum energy required for a reaction called?

  Activation energy
• How can the rate of a reaction be increased?

  Increase frequency or energy of collisions
• What factors can increase the frequency/energy of collisions?

  Temperature, pressure, concentration, surface area, catalyst
• How does increasing temperature affect reaction rates?

  Increases kinetic energy, leading to more collisions
• How does increasing pressure affect reaction rates in gases?

  Increases number of particles in a volume
• How does increasing concentration affect reaction rates?

  Increases number of particles in a volume
• How does increasing surface area affect reaction rates?

  Increases frequency of collisions
• How can you graphically find the rate of reaction?

  • Draw tangents to curves
  • Use slope of tangent as rate
  • Steeper line indicates greater rate change
• What does a steeper line on a reaction graph indicate?

  Greater increase or decrease in rate
• What should you check when interpreting a reaction graph?

  If it shows a product or reactant

  
• What happens to the mass/volume/concentration of a product over time?

  It increases during the reaction
• What happens to the mass/volume/concentration of a reactant over time?

  It decreases during the reaction
• What is a catalyst?

  A substance that speeds up reactions
• How do catalysts affect the products of a reaction?

  They do not alter the products
• What happens to catalysts at the end of a reaction?

  They remain unchanged in mass and composition
• How do catalysts increase the rate of reaction in terms of activation energy?

  They decrease activation energy required for reactions

  
• How do catalysts affect the proportion of particles that can react?

  Increases proportion of particles with energy to react
• What are enzymes?

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

  Yeast
• What is produced from sugars during fermentation by yeast?

  Ethanol
• What is ethanol commonly found in?

  Alcoholic drinks
• What changes in heat energy accompany salts dissolving in water?

  Temperature changes can be measured
• What type of reaction is a neutralisation reaction?

  Exothermic
• What type of reaction can displacement reactions be classified as?

  Exothermic or endothermic
• What type of reaction is precipitation?

  Exothermic
• How can temperature changes be measured during reactions in solution?

  Using a thermometer in a polystyrene cup
• How is an exothermic change defined?

  Heat energy is given out
• What happens to the temperature of surroundings during an exothermic reaction?

  It increases