How Many Drops?

http://www.teachengineering.org/view_lesson.php?url=collection/duk_/lessons/duk_drops_mary_less/duk_drops_mary_less.xmllessontext/xmlHow Many Drops?Engineering K-Ph.D. Program, hypothesisvariablescontrolsexperimental designsurface tensionhypothesiscohesionsurface tension

In this lesson and its associated activity, students conduct a simple test to determine how many drops of each of three liquids can be placed on a penny before spilling over. The three liquids are water, rubbing alcohol, and vegetable oil; because of their different surface tensions, more water can be piled on top of a penny than either of the other two liquids. However, this is not the main point of the activity. Instead, students are asked to come up with an explanation for their observations about the different amounts of liquids a penny can hold. In other words, they are asked to make hypotheses that explain their observations, and because middle school students are not likely to have prior knowledge of the property of surface tension, their hypotheses are not likely to include this idea. Then they are asked to come up with ways to test their hypotheses, although they do not need to actually test their hypotheses. The important points for students to realize are that 1) the tests they devise must fit their hypotheses, and 2) the hypotheses they come up with must be testable in order to be useful.

The engineeirng connection in this lesson is when students design experiments to test their hypothesis. Scientists practice engineering whenever they design new experiments to test hypothesis. Students will be able to give an example of a hypothesis that is based on an observation of a natural phenomenon. Students will be able to give an example of an experiment designed to address a specific hypothesis. Students will be able to distinguish between the variable and controlled conditions in an experiment. 1TeachEngineering.orgMary R. Hebrank (Project Writer and Consultant), Duke UniversityS1028413North_CarolinaScience1.01 Identify and create questions and hypotheses that can be answered through scientific investigations.66S1028415North_CarolinaScience1.02 Develop appropriate experimental procedures for: • Student generated questions.66S1028419North_CarolinaScience1.04 Analyze variables in scientific investigations. • Identify dependent and independent.66S102841ENorth_CarolinaScience1.05 Analyze evidence to: • Explain observations.66S1028428North_CarolinaScience1.08 Use oral and written language to: • Defend conclusions of scientific investigations.66S10284AFNorth_CarolinaScience1.01 Identify and create questions and hypotheses that can be answered through scientific investigations.77S10284B1North_CarolinaScience1.02 Develop appropriate experimental procedures for: • Student generated questions.77S10284B5North_CarolinaScience1.04 Analyze variables in scientific investigations: • Identify dependent and independent.77S10284BANorth_CarolinaScience1.05 Analyze evidence to: • Explain observations.77S10284C4North_CarolinaScience1.08 Use oral and written language to: • Defend conclusions of scientific investigations.77S1028531North_CarolinaScience1.01 Identify and create questions and hypotheses that can be answered through scientific investigations.88S1028533North_CarolinaScience1.02 Develop appropriate experimental procedures for: • Student generated questions.88S1028537North_CarolinaScience1.04 Analyze variables in scientific investigations: • Identify dependent and independent.88S102853CNorth_CarolinaScience1.05 Analyze evidence to: • Explain observations.88S1028546North_CarolinaScience1.08 Use oral and written language to: • Communicate findings.88S102855ENorth_CarolinaScience3.01 Analyze the unique properties of water including: • Universal solvent.88S1028574North_CarolinaScience3.07 Describe how humans affect the quality of water: • Point and non-point sources of water pollution in North Carolina.88S1028587North_CarolinaScience4.05 Identify substances based on characteristic physical properties: • Density.88United StatesCopyright 2012 - Engineering K-Ph.D. Program, Pratt School of Engineering, Duke Universityhttp://www.teachengineering.org/policy_ipp.phphttp://www.teachengineering.org/2010-03-067Teacher