Experimental know how

• What do reliable results come from?

  Experiments that give the same data
• What defines valid results in experiments?

  Results that are reliable and fair tests
• How can you improve the reliability or validity of experimental results?

  • Control variables to improve validity
  • Carry out repeats to improve reliability
• What is a variable in an experiment?

  A factor that can change
• What is the independent variable in an experiment?

  The variable you change
• What is the dependent variable in an experiment?

  The variable you measure
• What are control variables?

  Variables kept the same in an experiment
• Why is a control experiment used?

  To see what happens without changes
• How can you improve reliability in measurements?

  By repeating measurements and calculating the mean
• How many times should each measurement be repeated?

  At least three times
• What are potential hazards in experiments?

  Things that can cause harm or danger
• What should you do if working with sulfuric acid?

  Wear gloves and safety goggles
• What is a fire hazard in a lab?

  An unattended Bunsen burner
• How can you reduce risks when using a Bunsen burner?

  Stand it on a heatproof mat
• What should you do if chemicals give off harmful gases?

  Use a fume cupboard
• What defines accurate results?

  Results close to the true answer
• How can you measure the rate of a chemical reaction accurately?

  By collecting gas with a gas syringe
• What must you ensure when using a gas syringe?

  It is empty at the start
• What are precise results?

  Data close to the mean of repeated results
• How do data sets compare in terms of precision?

  • Data set 1: 12, 11, 14, 13 (Mean = 13)
  • Data set 2: 14, 17, 14 (Mean = 14)
  • Data set 1 is more precise than data set 2.
• How does precision differ from accuracy in results?

  Precision is closeness to the mean
• What is the importance of measuring correctly in experiments?

  To ensure accurate and reliable results