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Initial Model

Initial Model. The initial model states that an evaporating liquid cools a body (test tube, person, etc.) that it evaporates off of by taking thermal energy from that body

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Initial Model

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  1. Initial Model • The initial model states that an evaporating liquid cools a body (test tube, person, etc.) that it evaporates off of by taking thermal energy from that body • The thermal energy is used by the surface liquid to change from a liquid to a gas, a phase change which requires lots of energy

  2. Question • The proposed question is, “What is the relationship between the rate a liquid evaporates and the cooling effect of that liquid?”

  3. Hypothesis • We hypothesized that the faster a liquid evaporates, the greater the cooling effect, because more of it will evaporate FASTER COOLING SLOWER COOLING FASTER EVAPORATING SLOWER EVAPORATING Alcohol Water Gatorade Sweat Salt water Saturated salt water Oil (1.01% NaCl) (4.96%) (10.08%)

  4. Methods • Seven test tubes were wrapped in paper towel and filled with warm water • The paper towel was then soaked with one of the seven liquids and temperature was measured at regular intervals for 20 min.

  5. Evidence • Alcohol, various salinities of saltwater, water, and Gatorade evaporate easily at room temperature • Canola oil has a much slower evaporation rate • Test tubes wetted with alcohol, various salinities of saltwater, water, and Gatorade had similar cooling rates, while oil had a slower cooling rate

  6. Evaporates easily Alcohol (15min) Water (60min) Gatorade (95min) Sweat (170min) Middle salinity (200min) Saturated saltwater (200min) Doesn’t evaporate Canola oil Rates of Evaporation

  7. Cools effectively Alcohol Water Gatorade Sweat Middle salinity Saturated saltwater Doesn’t cool Canola oil Rates of Cooling

  8. Final Claim • The test tubes that were wetted with substances that evaporated well had faster cooling rates • Some liquids evaporate more quickly using less energy while others evaporate more slowly using more energy, thus the cooling rates of the water is similar with different surface liquids • (We’re lucky we don’t sweat Canola oil)

  9. Assumptions • Cooling was due to evaporation, not some other phenomenon • Heat loss due to convection was the same for all liquids and all test tubes • The equipment did not contribute to any of the cooling differences between test tubes

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