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Acitivity 7 - How does Water Affect Life on Earth?

PART I: HOW DOES WATER AFFECT LIFE ON EARTH?

Estimated Time of Activity: 90 minutes

Goals: Process Skills and Content Knowledge:

  • Students will learn what the Hydrological cycle is.
  • Students will learn the water quality factors that scientists observe in the field.
  • Students will learn what Transparency, Dissolved oxygen, Salinity and pH is.
  • Students will learn about the pH scale.
  • Students will measure and monitor pH of pond water.
  • Students will learn how to create a lab report.

Materials:

Activity Instructions:

  1. Ask Students: What are Biotic/Abiotic factors?
  2. Ask Students: What were some abiotic factors that were part of the clam shrimp habitat? List on board.
  3. Tell students that the next workshops are going to deal with WATER (an abiotic factor of the clam shrimp habitat).
  4. Tell students that in order to understand effects of water on life, you have to understand where it comes from.

THE HYDROLOGICAL CYCLE

            - The Water cycle is also known as the HYDROLOGICAL cycle.

  1. Have students write the steps of the hydrological cycle on their worksheet as you go through on board.
    1. Water vapor EVAPORATES into the atmosphere from oceans, rivers, lakes, soils and vegetation (TRANSPIRATION).
    2. When water reaches the atmosphere it cools, or CONDENSES and turns into liquid water or ice to become clouds.
    3. When water droplets or ice crystals get large enough, they PRECIPITATE or fall back to the earth’s surface.
      1. What are some forms of precipitation?
        1. Rain
        2. Snow
    4. Once on the ground, water INFILTRATES the soil and is either absorbed by plants or reaches the ground water and increases the WATER TABLE.
    5. If water does not filter into the soil, it runs off into streams and rivers and eventually into oceans, and the process starts all over again.
  2. Have students label the water cycle diagram and go over it.
  3. Tell students that there are many factors that aquatic scientists look at to determine how healthy the water is in a system. Have students list these factors and how they affect life found in water, and what tools scientists use to measure them. Show students the different equipment used to test each water quality factor.
    1. Transparency –
      1. Transparency is the degree to which light penetrates into water.
      2. Light, essential for growth of green plants, travels farther in clear water than in turbid water that contains suspended solids or colored water.
      3. Two methods commonly used to measure transparency are the Secchi disk and transparency tube.
    2. Water Temperature –
      1. amount of solar energy absorbed by the water.
      2. 51% of incoming Solar energy is absorbed by the land and oceans and the rest is absorbed by the atmosphere, clouds or is reflected back to space
      3. Increase in Solar energy à Increase in temp.
      4. Each kind of animal has a certain temperature range that they can tolerate. It is harder for animals in water to adapt to temperatures that are not suitable for them. Ask student what they do in the winter when it gets cold or when it gets hot in the summer?
      5. Ask students what is used to measure water temperature? Scientists use thermometers to measure temperature
    3. Dissolved Oxygen
      1. Molecules of oxygen that have mixed in with the water.
      2. Without sufficient levels of oxygen in the water, aquatic life suffocates.
      3. Scientists use titration kits, to measure the dissolved oxygen. Remind students of the titration experiments that they did earlier in the semester where they had to determine threshold values.
    4. Salinity
      1. The measure of how salty the water is.
      2. Can we drink salty water and survive? Every animal that lives in the water can tolerate a certain range of salinity. Animals found in
        1. Freshwater can tolerate up to 0.5 ppt
        2. Brackish water → 0.5 – 35 ppt
        3. Ocean/Saltwater → 35 – 50 ppt
      3. Scientist can use a water meter or an instrument called a refractometer to measure the salinity of water.
  4. What is pH? The measure of acid content of water. It is the measure of H+ in solution. The more acidic a solution, the more H+ ions there are.
  5. pH – scale → 0 – 14
    1. Pure water has a pH of 7 (neutral)
    2. pH below 7 → acid
    3. pH above 7 → basic
  6. How factors affect the pH level of water?
    1. Vegetation type and density
      1. Organic acids are naturally found in plants (sphagnum moss – bogs; several tree species). When they decay in the water à Decrease in pH.
      2. When this material decomposes carbon dioxide is released. The carbon dioxide combines with water to form carbonic acid. Although this is a weak acid, large amounts of it will lower the pH.
    2. Underlying strata of rocks and soil
      1. One of the most important factors is the bedrock and soil composition through which the water moves, both in its bed and as groundwater. Some rock types such as limestone can, to an extent, neutralize the acid while others, such as granite, have virtually no effect on pH.
      2. Limestone – increases the pH (basic)
    3. Acid rain
      1. Air pollution from automobiles and coal-burning utilities and factories
      2. Sulfur Dioxide and nitrogen oxide are emitted from tailpipes and smoke stacks
      3. When SO2 and NO2 combine with water in the atmosphere, they form sulfuric and nitric acids which fall to earth in the different forms of precipitation (?) This precipitation mixes with surface water in creeks, rivers, ponds and wetlands.
      4. Acid rain is responsible for many of our first order streams becoming acidic. Serious problems can occur in spring when streams receive a massive acid dose as acidic snows melt.
    4. Humans
      1. dumping of chemicals into the water by individuals, industries, and communities. Remember - something as "harmless" as shampoo rinse water is actually a chemical brew and can affect the pH along with other chemical parameters of water.
      2. Many industrial processes require water of exact pH readings and thus add chemicals to change the pH to meet their needs. After use, this altered pH water is discharged as an effluent, either directly into a body of water or through the local sewage treatment plant.
  7. pH range preference
    1. pH of natural systems under normal circumstances is typically between 6.0 and 8.0. This is the most favorable range for life, although some organisms can tolerate harsher conditions
    2. Sudden, dramatic changes in pH could endanger the lives of young animals
    3. Ask students- What is the pH of a healthy lake?
    4. At what pH would fish die? Frog eggs, tadpoles, crayfish die? Is rainbow trout a fish that is sensitive to pH?
  8. What are buffers?
    1. Something that neutralizes acids and bases in a solution.
    2. Chalk (calcium carbonate CaCO3), baking soda (NaHCO3) and antacids act as buffers. Mix these with lemon juice and vinegar and see the change in pH.
  9. What are the different ways to measure the pH of water?
    1. There are many ways to measure pH. These are the three frequently used tests.
      1. Hydroion paper – read the whole scale 0 – 14,
      2. red and blue litmus paper –
        1. red turns blue in presence of base – stays red in presence of base;
        2. blue turns red in presence of acid and remains blue in the presence of a base;
      3.  pH meter – reads the amount of H+ ions in a solution.
  10. Present the Water Data Analysis Information chart that the students will be filling during the following lectures on Salinity, Dissolved Oxygen, pH,
  11. Have them fill out a row for pH and go over.
  12. Assign student groups topic of research: pH, Salinity, and Dissolved Oxygen

 

ACTIVITY:

  1. Give students a list of household liquids. → Soil and water; vinegar; baking soda, water, orange juice, milk, ammonia, coke.
  2. In groups, have them discuss the order from most acidic to most basic and have them create a list. Inform students that by making the list, they are formulating a hypothesis of what liquids are more acidic than others?
  3. Have each group write their list on the board in the order they think it appropriate.

PART II: HOW DOES WATER AFFECT LIFE ON EARTH?

Estimated Time of Activity: 90 minutes

Goals: Process Skills and content Knowledge:

  • Students will learn about the pH scale.
  • Students will learn how to test for pH on different household liquids.
  • Students will learn how to create a Lab report.

Materials:

  • 8 cups (Sep cups?)
  • Soil and water
  • vinegar
  • baking soda
  • water
  • orange juice
  • milk
  • ammonia
  • coca-cola
  • pH paper (8 strips each)  - blue / pink and color pHast

Activity Instructions:

1. Tell students that aquatic scientists also create lab reports to record the data from their observations and share it with other scientists.

Today each of you is going to be an Aquatic Scientist. As we look at the pH of different substances, we will learn how to create a Lab report to share with the other scientists in the classroom.

2. Go over the parts of a Lab report.

TITLE:  

HYPOTHESIS: A hypothesis is often referred to as an “educated guess,” which is a prediction that will be tested in the experiment.

EXPERIMENTAL DESIGN:  This may also be called the Procedure or Experiment.

DATA:   These are the results of the experiment, presented in one or more of the following formats: tables, graphs, or drawings (the form the data takes is dependent on the experiment).   Previous    Top    Next

CONCLUSION:   The conclusion should make reference to the PROBLEMHYPOTHESIS (if there is one), EXPERIMENTAL DESIGN (especially in terms of the validity of the DATA), and the DATA.  All conclusions should be driven by the data.  It is essential that the student discuss any factors that may have affected the validity of the data, and (depending upon the lab or teacher) describe how to improve the lab.   

3. Have students create the appropriate experiment to test their hypothesis.

Assignments:

  • If lab report is not completed in class, have students complete at home.
  • Have students think of a chart for data collection of the different water quality parameters by day.
Date Salinity (ppm) DO (ppm) pH Temperature Turbidity

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Assessment:

Lab reports will be graded to see if students were able to write an appropriate procedure, record data and draw an appropriate conclusion for their experiment.

 

Return to ARM introduction.