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SCIENTIFIC METHOD

What you see… Pet dog going crazy scratching himself. a hypothesis supported by repeatable evidence, Scratching Dog Theory: Dogs that scratch have fleas. How Science Works. Test the Hypothesis… Buy Pluto a flea-collar Control: Pluto without a flea collar Treatment:

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SCIENTIFIC METHOD

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  1. What you see… • Pet dog going crazy scratching himself • a hypothesis supported by repeatable evidence, Scratching Dog Theory: • Dogs that scratch have fleas How Science Works.... Test the Hypothesis… Buy Pluto a flea-collar Control: Pluto without a flea collar Treatment: Pluto with a flea collar Replication!!! 30 Plutos! • Educated guess… • “He has fleas.” • or • “He has dry skin.” or… observations theories • But Remember…. • conclusions either reject or support hypothesis, never prove it! • (have we ruled out dry skin??) SCIENTIFIC METHOD conclusions • Interpret your experimental results… • No more scratching, your carpet is a flea graveyard! questions • What you ask… • “I keep a clean house, so why’s he scratching?” experimentation hypotheses

  2. Experimentation... • Allows us to study causation • Not just correlation • Lab studies • Field studies • experimental (treatment) group… • The treatment where you manipulate the variable of interest • Control Group • Do every thing you did in the experimental group… • ….except, leave out the variable of interest • Do analysis (usually use stats.)

  3. Scientific Measurements

  4. Uncertainty in Measurement • Many properties of matter are quantitative: • Associated with a number. • Units used in science are the metric system. • SI Units: • Today’s system developed in 1960.

  5. Physical Quantities • Powers of ten are used for convenience with smaller or larger units in the SI system.

  6. Prefixes • Need to memorize some of the above selected prefixes and be able to convert from one prefix to another.

  7. Temperature • Fahrenheit: Define 32oF as the freezing point of water and 212oF as the boiling point of water at sea level. • Kelvin: Define 0K as the lowest attainable temperature of -273.15oC (absolute zero). • Don’t use oK.

  8. Volume

  9. The Density Concept • Each cube represents a volume of 1 cm3. As the mass increases, the density increases.

  10. We will figure out the density of zinc in lab • Density: • Used to characterize substances. • Defined as mass divided by volume: • Units: g/cm3, g/mL, g/L. • Density of water is 1.00 at 250C. • Density is temperature dependent!

  11. Volume by Displacement • The difference between the initial and final water levels is equal to the volume of the solid jade.

  12. Volume by Displacement • The volume of water displaced is equal to the volume of oxygen gas produced by the sample.

  13. Precision and Accuracy in measuring the density of zinc • Precision: • How closely individual measurements agree with one another. • Accuracy: • How closely individual measurements agree with the correct value.

  14. Heat and Specific Heat • Heat measures the total energy of a system. • Temperature measures the average energy of a system. • Specific Heat – Amount of heat (in calories) necessary to raise the temperature of 1g of any substance by 1oC.

  15. Heat and Specific Heat • Each cube represents 1 g of substance receiving 1 cal of heat. The temp. change varies with the substance.

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