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Science 10
Unit 1, Lesson 5: Properties of Water Key
(7+5=12 Marks)
Check your Understanding questions 1-7 on page 78 in your textbook.
1. A covalent bond is an intramolecular bond formed by the mutual attraction of two atomic nuclei to a
shared pair of electrons. A hydrogen bond is an intermolecular attraction between a partially positive
negative atom, such as oxygen, on another molecule.
2. Water is polar because of its “bent” shape. If a water molecule was straight instead of bent, there
would be no positive and negative poles. The polarities of the two bonds would balance one another.
3. Water has an unusually high melting point, boiling point, ability to absorb thermal energy without
increasing in temperature (specific heat capacity), and surface tension. Water is also unusual because
it is more dense in the liquid state then in the solid state.
4. Surface tension is due to the unusually strong cohesiveness of molecules at the surface of a liquid. In
the case of water, this phenomenon is due to the fact that water molecules form hydrogen bonds with
nearby molecules at the surface and within the water. Because of its strong surface tension, water
forms droplets when it rests on a substance such as the metal of a car. (On a surface that attracts
water molecules more strongly than the molecules attract one another, droplets would not form.) Oil
would not behave in the same way because oil molecules are non-polar and cannot form hydrogen
bonds.
5. When cooled, water molecules form rigid crystals held together by hydrogen bonds. As a result, ice
is less dense and takes up more volume than the same mass of water. A glass container would crack
with the expanding ice. Oil becomes denser and occupies less volume when it freezes, so it would be
safe in a glass container.
6. Because ozone is made of three identical oxygen atoms, none of the bonds are polar. As a result, the
molecule as a whole is not polar, despite its bent shape.
7. The hydrogen bonds between the water molecules and the glass are stronger, because the meniscus is
concave. The water molecules are more attracted to the glass than to one another, so they “climb” the
glass walls.
Properties of Water Quiz = ?/5
Sci10U1L5Key
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