A look at Water and Its Contaminants_P1

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MEETING RAISES FISH KILL CONCERNS

Read the article on page 22 and answer the questions.

1.What is the danger to Riverwood citizens?

2. Why will the EPA be collecting water samples? Why must this be done

hourly?

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MEETING RAISES FISH KILL CONCERNS

1. What is the danger to Riverwood citizens?

There is no obvious cause to the Fisk Kill

2. Why will the EPA be collecting water samples? Why must this be done hourly?

To look for unusual fluctuations in dissolve oxygen levels, as fish take in adequate oxygen dissolved in water.

3. What signs of "biological trauma" were found in all of the dead fish?

Scientists have been unable to identify any microorganisms in the fish that could have been responsible for their death.

4. What has Dr. Brooke reported to be a possible cause the fish kill? Why?

It must be have been something dissolved or temporarily suspended in the water. Considerations would include the relative amounts of various

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Section Overview

• _{Understand about Chemistry of Water and How}

Substances Interact with Water

• _{Know the Properties of water}

• _{Be able to Classify Mixtures as Suspensions, Colloids or}

Solutions

• _{Begin to know the universal symbolic language of}

Chemistry

• _{Be able to distinguish between pure water and clean}

water

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Demonstration

Pouring Water Sideways

Is there an explanation for this?

Surface Tension

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Discover Activity 1: Can you make a

paper clip float?

Materials

bowl of water

paper towels

paper clips

Procedure

Drop a paper clip in a cup of water. What happens?

Tear off a piece of paper towel that is slightly larger than

the paper clip.

Place the piece of paper towel on top of the water.

Gently place another paper clip on the piece of paper

towel.

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If you drop a paper clip in water, the paper clip sinks. But if you put the paper clip on a piece of paper towel, the paper towel sinks and the paper clip floats.

This is because water particles are attracted to each other in all directions, making them "stick" together.

However, because there are no water particles above them, the water particles at the surface "stick" only to particles next to and below them. This makes the surface act as if it had a thin "skin".

The paper towel helps you to lower the paper clip onto the surface gently without breaking the surface tension.

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Density – a derived unit

• It’s a characteristic property

(constant for a substance)

• Density – mass per unit volume

of a substance

• D = m/v

• Can’t measure it directly: mass

object, then get volume by

pouring into graduated cylinder

or use water displacement for

solids, then calculate it.

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DENSITY

In the foul water laboratory activity you observed

that coffee grounds settled to the bottom of the

water sample, where as oil ‘floated’ on top.

Explain this observation in relation to the relative

densities of coffee grounds, water and oil.

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DENSITY

How does the density of ice compare with that of

liquid water?

The Density of solid Ice is less than water, which is

why an ice cube floats when placed in water.

What would happen to rivers and lakes (and fish) in

cooler climates if the relative densities of ice and

liquid water were reversed?

If this was reversed, ice would settle to the bottom,

and in rivers and lakes of the colder climates the

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DENSITY

Suppose you were given a small cube of copper metal. What

measurements would you need to make to determine its

density?

Mass and volume have to be determined.

How would you make these measurements in the laboratory?

In the laboratory, a balance could be used to determine the

mass. Its volume can be determined by measurement-length

times width times height if a regular shaped object and if

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DENSITY LAB

Density

is an important property in chemistry. It can be used as

a test to help identify a substance. Density is the relationship

between the mass and the volume of a substance.

Purpose:

• To determine the density of two common liquids: water (H

₂

O)

and ethyl alcohol (C

₂

H

₅

OH).

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DENSITY LAB

Materials:

• _{lab balance}

• _{graduated cylinder}

Procedure:

• _{Make an organized table of results in your science notebook.}

• _{Measure the mass and the volume of three different amounts}

of water and three different amounts of ethyl alcohol.

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DENSITY LAB

Data Analysis:

• _{Make an organized table of results in your lab notebook.}

• _{Use a ruler.}

• _{Type your results into the computer. We will produce a}

graph of everyone's results.

• _{When you receive your copy of the graph, explain any}

relationships you notice.

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Density Lab

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Density Lab

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Density Lab

• _{Was your experimental value the same as the}

actual value?

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Predict

Based on the Densities of the two elements,

what order would you expect them to be in

placed in the same container.

Add a color to the water and then pore them

in the order you expect.

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