THE SCIENTIFIC METHOD PHYSICS AND CHEMISTRY REVISION 1 We observe that when a glass bottle filled with water is left in the freezer, it breaks. Which of these are valid hypotheses? Why? a) Low temperature causes glass to break. b) The volume of water increases when it freezes. c) The force exerted by the water breaks the glass. 2 Convert these units: a) 5 L ® cm3 d) 100 dm3 ® m3 b) 5 atm ® hPa e) 1 000 mmHg ® atm c) 0.05 m3 ® L f ) 70 kPa ® atm A C T I V I T I E S QUANTITIES, UNITS AND CONVERTING UNITS A quantity is a property of matter that can be measured . It can be written as a number and a unit. We use a conversion factor to change one unit into another unit. Units of pressure hPa (hectopascal) ×100 : 100 Pa (pascal) : 101300 × 101300 atm (atmosphere) × 760 : 760 mmHg Units of volume m3 × 1000 : 1000 dm3 L × 1000 : 1000 cm3 mL A hypothesis is a possible explanation and it must be tested. Define the experiment: the quantities you want to measure, the conditions of it and the equipment. Analyse the data Use tables to collect the data and graphs to represent and analyse them. 4 3 5 2 6 1 Observe a phenomenon Science works by observing a phenomenon and asking questions about it. Publish the results The conclusions of scientific studies are often used to create laws and scientific theories. Experiment The hypothesis is tested by doing experiments that simulate the problem. Search for information Find out whether a solution already exists. Do you agree with it? Is there another possible explanation? Make a hypothesis Think about what you have found out and think of a reasonable answer or prediction. The results are published in articles and books. The scientific method is the set of processes and attitudes that we use to study and explain the phenomena that happen in the universe, and come to valid conclusions. A hypothesis is a provisional statement used in scientific research. It may or may not be true. S O LV E D P R O B L E M 1 Write 120 hPa in mmHg. Use a conversion factor for each change of unit: 120 760 900 hPa 100 Pa 1 hPa 1 atm 101 300 Pa mmHg 1 atm mmHg ⋅ ⋅ ⋅ = Conversion factor Conversion factor Conversion factor 10
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