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Solving Problems in Science

This book provides a comprehensive guide to solving problems in science using the International Junior Science Olympiad (IJSO) approach. It covers topics such as observation, hypothesis, experiment, analysis, theory, prediction, and modifying theories as needed. The book also explains the scientific method, precision, accuracy, significant figures, control experiments, variables, and experiment setup. It includes an exercise on determining answers with significant digits and explores a photosynthesis experiment to understand the importance of light.

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Solving Problems in Science

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  1. Solving Problems in Science International Junior Science Olympiad (IJSO) Dr. Yu-San Cheung yscheung@cuhk.edu.hk Department of Chemistry The Chinese University of Hong Kong

  2. Observation  Hypothesis  Experiment  Analysis  Theory  Prediction  Experiment Modifying theory as needed Law Scientific Method

  3. Precision vs. Accuracy • Precision(精密度) • representing the agreement between repeated measurements of the same quantity • Accuracy(準確度) • representing the agreement between a measured value and the true quantity

  4. Significant figure: • Multiplication and division: keep the smaller number of significant figure • Decimal place: • Addition and subtraction: keep the smaller number of decimal place

  5. Exercise • Determine the answer for (a) to (f) below. Use the correct number • of significant digits in your answer. • 7.2 mm x 1.56 mm = • 99.5 cm2 x 0.0084 cm = • 63.6 g/ 2.7 cm3 = • 288 g/16.9 cm3= • 0.001 g + 5.3 g + 162 g = • 32.58 cm3 – 5.2 cm3 =

  6. Control Experiment A method of scientific investigation to demonstrate a cause and effect hypothesis. For example, a phenomenon occurs after a certain treatment is given to a subject, and that the phenomenon does not occur in the absence of the treatment.

  7. Variable in Control Experiment • Dependent variable • Quantity to be measured; • Quantity which is thought to be affected during the experiment; • Results of the experiment. • Independent variable • Quantity to be varied; • Quantity which is thought to affect the dependent variable(s); • Quantity which can be manipulated or controlled. • Controlled variable • Quantity kept constant or unchanged.

  8. Experiment Set-up Control Group vs Experiment Group • Control Group • Set-up • Procedures • Control Variables • Experiment Group • Set-up • Procedures • Control Variables • Independent Variables

  9. A Photosynthesis(光合作用) Problem The following experiment is designed to find out whether light is necessary of photosynthesis. • What is the hypothesis of this experiment? • If starch is present in region A but absent in region B after exposing the plant to sunlight for several hours, what would your conclusion be? • Which region is the control? Explain briefly.

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