Water Properties Lab
NAME:_______________________________ Date: ________________
Objectives:
1. After completing this lab you should be able to explain the importance of all of water’s properties.
2. After completing this lab you should be able to describe hydrogen bonding and its importance.
3. After completing this lab you should be able to describe why a water molecule is polar and draw a
water molecule.
Background: Water is everywhere. It makes up about 3/4ths of the surface of the earth. It makes up 5095% of the weight of living organisms. It is in the air we breathe, the sinks we use and in every cell of the
body. Water has special properties that make it unusual and complex. For instance, think about what
water can do by answering these questions:
1. How does water rise from the roots of a tree to the very top?
2. How do insects walk on the water?
3. Why does ice float rather than sink?
4. Why do people become seriously ill, or die, if they go without liquid for a week or so?
5. How would life in a lake be affected if ice sank and lakes froze from the bottom up?
Water has the ability to be a liquid, solid or gas depending on the temperature at which it is found. Each
molecule of water is made up of 2 hydrogen and 1 oxygen bonded together. Water is a polar molecule
because the oxygen molecule has a slightly negative charge and the hydrogen has a slightly positive
charge.
Part 1: Cohesion
Background: Water is attracted to other water molecules like magnets. This attraction is due to the
positive charge surrounding the hydrogen and the negative charge oxygen has. The negative oxygen of
one molecule is attracted to the positive hydrogen of another water creating a hydrogen bond. This is
attraction causes cohesion. Cohesion occurs when one water molecule sticks to another.
Materials:
Penny
Water
Medicine Dropper
Procedure:
1. Predict how many drops you will be able to put on the penny before it overflows by having each
person at your table guess.
Person
Number of drops
1
2
3
4
Average
2. Now, let’s see how many drops of water you can place on the surface of the penny before it overflows.
Drop water from the dropper onto the penny, keeping a careful count of each drop.
3. Draw a diagram below showing the shape of the water on the penny after one drop, when the penny
is half full and just before it looks like it is going to overflow.
4. How many total drops did you get on the penny? __________________
5. Explain your results in terms of cohesion.
Part 2: Adhesion
Background: Water not only sticks to other water molecules (cohesion) but it also sticks to substances
other than water (adhesion). Cohesive and adhesive forces are important for the transport of water
from the roots to the leaves in plants. These forces create a "pull" on the water column. This pull results
from the tendency of water molecules being evaporated on the surface of the plant to stay connected to
water molecules below them, and so they are pulled along. Plants use this natural phenomenon to help
transport water from their roots to their leaves. Without these properties of water, plants would be
unable to receive the water and the dissolved minerals they require.
Materials
Petri Dish
Beaker of Water
Medicine Dropper
Procedure:
1. Place a few drops of water on the inside of a petri dish.
2. Carefully turn the petri dish upside down.
3. Observe the results. Draw what you see below.
4. Describe what happened with the water and the petri dish in terms of adhesion.
Part 3: Density
Background: Water is one of the few substances that are less dense as a solid than as a liquid. While
most substances contracts when they solidify, water expands. This property is due to the hydrogen
bonding between water molecules.
Materials
Beaker of water
Ice Cube
Procedure
1. Place the ice cube in the water
2. Describe what happened.
3. Explain why this property is important to aquatic organisms.
Part 4: Universal Solvent
Background: Because of its high polarity, water is called the universal solvent. A solvent is a substance
that dissolves, or breaks apart, another substance (known as the solute). Polar solvent dissolves polar
solutes and nonpolar solvents dissolve nonpolar solutes. Since our body is made up mainly of water this
allows the water in our body to carry important nutrients from one location to another.
Materials
2 Plastic Cups
Oil
Water
Salt
½ Teaspoon
Stir Rod
Procedure:
1. Fill a plastic cups 1/3 to 1/2 full with water.
2. Fill a plastic cups 1/3 to 1/2 full with oil.
3. Put about a half-teaspoon of salt into the water in one cup and another half teaspoon of salt into the
oil in one cup.
4. Stir each for about 20 seconds or until dissolved.
5. Record your observations below.
Solvent
Description of Solute after 20
Seconds of Stirring
Oil
Water
6. Summarize what you found in your experiment, based on your recorded observations.
7. Which liquid (water or oil) makes a better homogenous solution? _____________________________
Part 5: High Heat of Vaporization and Specific Heat
Background: Water has a high heat of vaporization – the energy required to convert liquid to a gas.
Water’s high heat of vaporization helps moderate the Earth’s climate. Water also has a high specific heat
capacity. Specific heat is a measure of heat capacity and is the heat required to raise the temperature of
one gram of water one degree Celsius. Water, with its high heat capacity, therefore, changes
temperature more slowly than other compounds.
Analysis Questions:
1. Review your data and describe why each of the following characteristics are important to human life.
Water Property
Description
Importance to Life
Cohesion
Adhesion
Density
Universal Solvent
High Specific Heat
and High Heat of
Vaporization
6. Draw a molecule of water. Include the charges on the oxygen and hydrogen.
7. Draw a second molecule of water above and label a hydrogen bond.