Homework

• What is the independent variable in an experiment?

  The variable deliberately changed by the investigator
• What is the dependent variable?

  The variable that changes when the independent variable changes
• Why must control variables be monitored?

  To ensure they do not affect the dependent variable
• What is a hypothesis?

  A prediction about what will happen in an experiment
• What does the range of a variable refer to?

  The minimum to maximum value of a variable
• Why is it important to choose a suitable range?

  A small range may not show the full pattern
• What is an interval in an experiment?

  The gap between readings taken during measurements
• What problem arises if intervals are too large?

  You might miss changes in the pattern
• What makes a method valid?

  It must answer the question being investigated
• What is calibration in scientific measurements?

  Adjusting a scale for accurate measurements
• What is resolution in measurements?

  The smallest change a measuring instrument can detect
• What does it mean for a result to be accurate?

  It is close to the true value
• Can a measurement be precise but not accurate?

  Yes, if it is close to the mean but not true value
• What is an anomaly in experimental results?

  An odd result that does not fit the pattern
• What causes random errors?

  Unpredictable mistakes made by the experimenter
• How can we reduce the impact of random errors?

  By repeating readings and calculating the mean
• What are systematic errors?

  Errors that are consistent in one direction
• What is zero error?

  When a measuring instrument does not read zero
• How can you avoid systematic errors?

  By calibrating measuring instruments before use
• What does repeatable mean in an experiment?

  The same person gets the same results using the same method
• What does reproducible mean in an experiment?

  Different people get the same results using the same method
• What does uncertainty in measurements indicate?

  How much doubt there is in a measurement
• How do we calculate uncertainty?

  Uncertainty is half the range of measurements
• What is the uncertainty for the volumes 124, 126, 123, 125, 123 cm³?

  $1.5 \text{ cm}^3$
• How can we improve accuracy in measurements?

  By reducing errors and uncertainty
• What is continuous data?

  Data with numerical values like height
• What is categoric data?

  Data with word labels like eye color
• What type of graph is used for continuous data?

  Line graph
• What type of graph is used for categoric data?

  Bar chart
• What is the use of a gas syringe?

  • Measures volume of gas
  • Unit: centimetres cubed (cm³)
• What is the use of a measuring cylinder?

  • Measures volume of liquid or solution
  • Unit: centimetres cubed (cm³)
• What is the use of an electronic balance?

  • Measures mass
  • Unit: grams (g)
• What is the use of a stopwatch?

  • Measures time
  • Units: minutes (mins), seconds (s), hours (h)
• What is the use of a thermometer?

  • Measures temperature
  • Unit: degrees Celsius (°C)
• What is the use of a metre rule?

  • Measures length
  • Units: centimetres (cm) or millimetres (mm)
• What is the use of a micrometer?

  • Measures small lengths or diameters
  • Unit: millimetres (mm)
• What is the use of a voltmeter?

  • Measures potential difference
  • Unit: volts (V)
• What is the use of an ammeter?

  • Measures current
  • Unit: amps (A)
• What is the use of a joulemeter?

  • Measures energy
  • Unit: joules (J)
• What are the steps to make a pure, dry sample of a soluble salt?

  1. Measure acid into a beaker
  2. Warm the acid gently
  3. Add insoluble base and stir
  4. Filter to remove excess base
  5. Evaporate water to form crystals
  6. Dry crystals on filter paper