GRADE: Seventh

CONTENT STANDARD: Earth and Space Science

CONTENT TOPIC: Structure of the Earth

CONCEPT: There is a continuous movement of water from earth to air to earth.

CONTENT OBJECTIVE: 7I3.00 To understand the water cycle

INSTRUCTIONAL OBJECTIVE: The learner will:

3.01 list the areas of the earth that water circulates as it completes the water cycle
3.02 identify whether water is evaporating or condensing during the water cycle
3.03 list the steps of the water cycle and explain what is occurring in each step

I. Fresh Water
A. Where it is found
B. Abundance
II. Water Cycle
A. Evaporation
B. Transpiration
C. Precipitation
III. Water Collection
A. Rivers, lakes, and oceans
B. Ground water
C. Surface water

TN COMPONENT OF SCIENCE: Process of Science

TN GOAL:

To enable students to demonstrate the processes of science by posing questions and investigating phenomena through language, methods, and instruments of science.

1.5 EXPLAINING - Phenomena and related information are made understandable through discussion that culminates in a higher level of learning.

1.5a Interpret the meaning and significance of data presented in tables and graphs.

BENCHMARK: The graphic display of numbers may help to show patterns such as trends, varying rates of change, gaps, or clusters.

TIME REQUIRED:

Two instructional periods

Ten - 1 gallon milk jugs, medicine dropper, tall drinking glasses, plastic wrap, hot water, ice cubes, healthy plant, and plastic bags

We are going to discover how water circulates through the earth and the atmosphere through evaporation, transpiration, and precipitation.

We all know that in order for all living things to survive, they all require water. We obtain our water easily by drinking from a sink or water fountain. Well, how do plants get their water? (Rain.) How does the water that the plants use get into the air? (Evaporation and Transpiration) How does it leave the air? (When the air is saturated, precipitation develops.) Today we are going to cover all of the questions as we discuss the water cycle.

Water is the main substance that covers our earth. Only three percent of this water is fresh water that we are able to drink. (Demonstration on the usable fresh water.) Water is not made or destroyed, so you could say that water is a "recyclable product." The water cycle is a continuous movement of water between the earth and air. As the water cycle occurs, water passes through all three of its phases: solid, liquid, and gas. Water is gathered on the earth's surface in two primary ways. One way is it can be found in lakes, rivers, and streams. As water leaves the lakes, rivers, and oceans and enters the atmosphere, the water changes from a liquid to a gas. This process is called evaporation. The other way liquid is stored on the earth's surface is in plants. As the water leaves the plant through its leaves, the water again converts from liquid to gas, but this time it is called transpiration. (Demonstration of transpiration). In the atmosphere, the gas converts back to a liquid. When a large amount of the liquid builds up in the atmosphere, the liquid falls back to the earth as precipitation. The main form of precipitation is rain, but if the temperature is cold enough, we will get the precipitation in the from of snow. (Do activity of observing the phases of water.)

Once the precipitation reaches the earth, it can sink into the ground, which is known as ground water. The water that does not sink is called surface water and it usually runs into lakes, rivers, and oceans. The ground water is used by the plants and keeps circulating through the water cycle as it becomes a gas again through transpiration. Surface water simply evaporates and keeps going through the water cycle.

1. Usable Fresh Water: Take 10 empty gallon milk jugs and ask the students to imagine that all of these jugs are filled with water and represent all of the water on the earth. Have all of the students write down how much of this they think to be drinking water. Once everyone has guessed, take a medicine dropper and put nine drops of water into one of the jugs to show, proportionally, how much of the earth's water is drinking water. The rest of the water is salty, frozen, or too deep in the earth.

2. Transpiration: Take a healthy, well-watered plant and cover it with a plastic bag. Place the plant in a window for approximately 30 minutes. Observe the bag and the drops of water that cover its inside. These drops of water are a direct result of transpiration.

3. Observing the Phases of Water: Fill the drinking glass half full with the hot water. Place a piece of plastic wrap tightly over the opening. Place 5 or 6 ice cubes on top of the wrap and allow it to sit for about 5 minutes. Record all observations. After the 5 minutes, pick up the plastic wrap and feel the side that covered the glass.

1. Have the students complete the following graphs, either as groups or individually.

Graphs can be used to help convey information in an easier form. Look at the following sets of data concerning the earth's water supply. Use this information to complete the following graphs.

Graph I: The Earth's Fresh Water and Salt Water

Graph II: Sources of the Earth's Fresh Water

2. Have the students draw the water cycle on paper. Be sure to include the titles evaporation, transpiration, and precipitation.

Today, we learned about the water cycle. We learned about evaporation, transpiration, and precipitation, and we learned about ground water and surface water. Turn to a neighbor and describe two of the terms to them. Compare your drawings to be sure everyone has an accurate picture of the water cycle.

water cycle - the continuous movement of water between the earth and the air.

evaporation - the process by which liquid water changes to water vapor.

transpiration - the process by which plants release water vapor into the atmosphere through their leaves.

precipitation - how the water returns to the earth and is found in many different forms: rain, snow, sleet, and hail.

ground water - the water that sinks into the ground after it is precipitated

surface water - water that flows into the rivers, lakes, and oceans

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