Practicals

• What should you always keep in mind when answering practical questions in exams?

  Independent, dependent, and controlled variables
• What is the independent variable in an experiment?

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

  The variable that changes as a result
• Why are controlled variables important in experiments?

  They ensure results are accurate
• What equipment should you specify when taking measurements?

  The specific tool used for measurement
• What safety equipment should be used when working with chemicals?

  Goggles and gloves
• Why is it important to state obvious information in practicals?

  You might gain extra marks
• How can you reduce errors and uncertainties in measurements?

  Align your eye with the measurement
• What is the benefit of taking multiple measurements?

  To calculate a mean for accuracy
• How should answers be formatted in practical exams?


  In bullet points format
• What is the first step in microscopy using onion skin?

  Place a thin layer on a slide
• What is used to stain cells for better visibility?

  Iodine
• What should you do after placing the slide on the microscope stage?

  Turn on the microscope's light
• What is the purpose of using a graticule?

  To measure the size of cells
• What is the formula for converting micrometers to meters?

  Micro is $10^{-6}$
• What is the aim of the osmosis experiment with potato cells?

  To find sugar concentration in cells
• How do you prepare potato cylinders for the osmosis experiment?

  Cut equal size cylinders and remove skin
• What should you do after placing potato cylinders in sugar solutions?

  Weigh them after a set time
• What does a straight line on a graph of mass change against sugar concentration indicate?

  No osmosis occurs at that concentration
• What is the aim of the enzyme experiment?

  To determine optimum temperature or pH
• How do you start the enzyme experiment with amylase and starch?

  Mix solutions and start the timer
• What indicates that starch is still present in the enzyme experiment?

  The iodine turns black
• How do you determine the end point of the enzyme reaction?

  When there is no color change with iodine
• What should you plot against temperature or pH in the enzyme experiment?

  The time taken for starch breakdown
• What is the purpose of food tests?

  To identify nutrients in different foods
• What is the test for starch?

  Add iodine solution
• What color indicates the presence of glucose in the food test?

  Color changes from blue to orange
• What indicates the presence of protein in food tests?

  Biuret reagent turns purple
• How do you test for fats in food?

  Add cold ethanol and water
• What is the aim of the photosynthesis experiment?

  To determine light intensity's effect
• What is the independent variable in the photosynthesis experiment?

  The distance from the light source
• What is the dependent variable in the photosynthesis experiment?

  Volume of gas produced or bubbles
• How do you promote oxygen release in the photosynthesis experiment?

  Add sodium hydrogen carbonate
• What should you do before starting the photosynthesis experiment?

  Cut the stem of the pond weed
• What relationship does light intensity have with distance?

  Inverse square relationship
• How do you measure reaction times in the reaction time experiment?

  Drop a ruler and catch it
• What is the formula for calculating reaction time?

  $t =$$\sqrt{2s/a}$
• What is the acceleration due to gravity used in the reaction time experiment?

  $9.8 \text{ m/s}^2$
• What is the purpose of using a quadrat in ecology?

  To estimate population of organisms
• How do you calculate the total population using quadrats?

  Mean per square multiplied by total area