Student Handout 3.8.1
Drops on a Penny Investigation
Building Background Knowledge
Instructions: Read the following passage about the properties of water. Mark the text as follows:
Circle the key vocabulary about the properties of water in blue.
Underline the vocabulary that they do not understand in red.
Highlight the properties of water that are discussed in the reading.
Water has several special properties due to its attraction to other water molecules. These attractions between
molecules are called intermolecular forces. Because part of the water molecule is positively charged and part of
the water molecule is negatively charged, the molecules will tend to stick together: positive end to negative end.
Water molecules can also stick to other molecules that have partially positive and partially negative sides. These
molecules are called polar molecules. When any molecule is attracted to another like molecule, the property is
called cohesion.
Glass and plastic have polar surfaces to which water is attracted. When
water molecules stick to other non-water molecules, it is called adhesion.
Adhesion is responsible for the meniscus that water forms in a graduated
cylinder. Cohesion and adhesion lead to different properties of water that
make it a special molecule with unique features.
meniscus
Cohesion is responsible for the surface tension of water because water
molecules are attracted to each other and held together by hydrogen
bonds, which are strong intermolecular forces. Surface tension is the
property of water that binds the water molecules together to form a “skin.”
The cohesion between water molecules cause the molecules to stick
together and contract on the surface, which allows water strider insects to
move on top of it rather than fall into the water. This cohesion and surface
tension also cause the pain of a belly flop because the hydrogen bonds
provide resistance to the body’s mass all at the same time.
Another unique property of water is its high specific heat, which means that it takes a large amount of energy
to change the temperature of water one degree Celsius. In order to increase the temperature of the water, you
have to break the hydrogen bonds between molecules to allow each water molecule to have a greater kinetic
energy. Because water has strong hydrogen bonds, more energy is required to increase the kinetic energy than is
required for a molecule that does not have (or has fewer) hydrogen bonds, such as alcohol.
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The Write Path I Science Teacher Guide