A Model Estuary ActivityA Model Estuary Activity

Recall that an estuary is a body of water along the coast that is formed when freshwater from rivers flows into and mixes with saltwater from the ocean.

Today’s Purpose

1. To model 3 different estuaries: one that has been left in its natural state, one that has been turned into a golf course, and one that has been turned into a city.

2. To explore the effects that changing an estuary may have on the world.

One that has been left in its natural state

One that has been turned into a golf course

One that has been turned into a city

Materials

• Graduated cylinder• Damp sponge• Foil tray (notice the hole)• Paper towel• Beaker

Water INmL

Water OUTmL

DifferencemL

Land use

Water that goes in

Water that comes out

What are variables?

• Any factor or condition we use in science to search for the cause and effect of relationships in nature.

• We design an experiment, so that changes to one item cause something else to vary in a predictable way.

• These changing quantities are called variables.

Variables

1. Independent variable2. Dependent variable3. Controlled or constant variables

Independent and dependent variables

• The independent variable is the one that is changed by the scientist. As we change the independent variable, we observe what happens to the dependent variable.

• We are observing how the dependent variable responds to the change made to the independent variable.

Example

• If we open a faucet (the independent variable), the quantity of water flowing (dependent variable) changes in response--we observe that the water flow increases.

• What is the independent variable in your experiment?

• And dependent?

Control or constant variable• These are the quantities we want to remain

constant. • Example:

– if we measure how much water flow increases when we open a faucet, it is important to make sure that the water pressure (the controlled variable) is held constant.

– That's because both the water pressure and the opening of a faucet have an impact on how much water flows. If we change both of them at the same time, we can't be sure how much of the change in water flow is because of the faucet opening and how much because of the water pressure.

Questions to answer

1. Explain why a sponge was used to as a natural estuary, a paper towel was used for a golf course, and the tray was left bare for a city.

Discuss this question in your group then write your answer down

Questions to answer

2. Imagine that a company has dumped a highly toxic chemical into each of the 3 estuaries we have studied. Explain how the chemical would react in each estuary.

Discuss this question in your group then write your answer down