Chemistry:

Properties of Water

Introduction: Water is everywhere. It makes up about 3/4ths of the surface of the earth. It makes

up 50-95% 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. 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 molecules and 1 oxygen molecule bonded

together.

Part A: Property - Cohesion

▪ Lay your penny flat on the lab table.

Question: How many drops of water will fit onto the penny without running over the edges?

Guesstimate and write your answer here: Answer:_______________________________

▪ Using your dropper and bottle of water, place water drops onto the penny, one-at-a

time. Keep track of the number of drops you can fit before the water flows over the

edges.

1. How many drops fit onto your penny? Answer:______________________________

2. Repeat the experiment two more times to determine the average number of drops that can

be added to the surface of a penny

Trial Trial One Trial Two Trial Three

Average

Number of

Drops

Number of

Drops Added

to Penny

3. Why did you get the number of drops you did? Use what you observed to explain the

property of cohesion.

Part B: Adhesion

Place 10 drops of water on your table top. Try to merge the drops into 1 big one using a

toothpick.

1. Describe what happens.

Try to separate the big drop into small ones using a toothpick.

2. Describe what happens.

3. Using your knowledge of the properties of water, explain what you observed.

Part C: How many drops of soapy water can be added to the surface of a penny without

running over the edges? (Use the same procedure from part A but use soapy water)

Trial Trial One Trial Two Trial Three

Average

Number of

Drops

Number of

Drops Added

to Penny

1. Were you able to fit more drops on top of the penny using water or soapy water? Why?

2. Explain how the water didn’t spill right away when it started rising over the penny.

3. Explain how the water behaved when you moved it with the toothpicks.

Part D: Separating Contaminants from Water

Chromatography is a way to look at complex mixtures by separating them into their

components. The separation of a mixture into its components is a physical process; that is,

because the components of the mixture are not chemically combined, they can be separated

by physical means. In order to develop and apply methods of water remediation,

environmental engineers, must also be able to separate mixtures to remove the pollutant

components.

Here's how chromatography works: Different inks have different properties, such as how much

they can be dissolved in solvents. When you place chromatography paper into a solvent, the

solvent begins to move up the paper. As the solvent rises, it dissolves the ink on the paper and

separates the ink into its components. The farther the ink travels, the more it is attracted to the

solvent.

Understanding chemical reactions can also help environment engineers remediate

contaminants in water. For example, engineers can use chemical oxidants to degrade certain

contaminants; in other words, the contaminant reacts with the treatment chemical to produce

a product that is benign, or harmless, unlike the contaminant. Some common indicators of

reaction include: changes in odor, temperature, or color, production of gas, or precipitation.

However, the only way to be absolutely certain of whether a chemical reaction has occurred is

to perform a chemical analysis to determine whether a new chemical is present. Most

experiments and data gathering done for the purpose of improving groundwater quality

involve the preparation of solutions to monitor and test contaminated water.

Directions:

1. Cut the chromatography paper into strips about two-inches wide. Cut at least six strips for

each group.

2. Take the strips of chromatography paper and fold both pieces about an inch from the

top.

3. Use a black Sharpie to draw a horizontal line near the other end of the chromatography

paper. Make the line about as high off the bottom as the width of your thumb.

4. Use a pencil to suspend the paper in each beaker, making sure the strip does not touch

the sides of the beaker.

5. Carefully add water to one beaker and alcohol to the other. Add just enough of each

liquid so that it touches the bottom of the hanging strip.

Data & Observations:

Write down your observations. Did the colors run? Did they separate in different colors? Which

colors can you detect? Which colors are on the top (meaning they ran quickly) and which are

on the bottom (meaning they ran more slowly)? How many color components does each

marker color have? Can you identify which colors are the result of a mixture of color

components and which ones are the result of one hue of color molecule? Are individual color

components brightly colored or dull in color? How many different colors can you detect in

total?

Draw diagrams of your finished chromatography separation.

Conclusion:

1. State your conclusions to this experiment. Be sure to support your analysis with data from the

experiment. Explain which colors were mixtures or pure substances and why.

2. Explain how chromatography works.

3. Were the mixtures homogeneous or heterogeneous? Explain why.

4. Did this lab use physical or chemical properties? Explain how you know and state the

properties.