Waves in the Water

Engagement

20-25 Minutes

Review the data on the student maps from Investigation 1. How long did it take for the toys to reach the shore after they were spilled? What might affect their speed and movement? Explain that in this activity they will be looking at one factor that helps to determine how an object moves from point A to point B on the ocean.

Ask the students: “What are the factors that affect how long it takes for the toys to reach the shore?” and have them write the question in their science notebook. Give the students two minutes to write their own answers, then have them share answers with a partner for two minutes. Each pair of partners can then join with another pair, forming a group of four to share and compile answers for two additional minutes. As a whole class, write a list of factors on the board as each group reports.

Factors that should come up are waves, wind, currents, tides, storms, and possibly others. Ask students to think about which factor is most important and explain why in their science notebook.

Exploration​

6-90 Minutes

Tell the students that they will be learning about waves. Assess prior knowledge as you develop a definition of “wave” through discussion, brainstorming, or another pair-sharing activity. Some definitions found in the dictionary:

A ridge or swell moving through or along the surface of a large body of water.

A disturbance traveling through water by which energy is transferred from one particle of water to another without causing any permanent displacement of the water itself.

A movement up and down or back and forth.

A disturbance, oscillation, or vibration, of water and moving through the water.
Ask for a volunteer to draw a wave on the board or overhead. Discuss, in general terms, the different parts of the wave that might be of interest as you study water motion. (For example “the top of the wave, the bottom of the wave, the distance from the top of the wave to the bottom, the distance from one high point to the next.)

Ask students to draw a wave in their science notebooks and to label its parts correctly. View a wave animation or project a diagram on the overhead projector for student use. Discuss the definitions of amplitude, wavelength, crest, trough, and equilibrium (still water or calm sea) level as they are labeling the parts of the wave. View the wave animation to see how energy moves through the water to create waves. Discuss the definitions of “period” and “frequency” and count the waves in the animation to find the period and frequency. If an online computer with a projector is not available, use a drawing on the board or overhead projector to talk through the concepts with the students. Ask students to add “period” and “frequency” to their wave diagrams and explain their meaning in their notebooks.

Water Wave Motion Lab (45-60 minutes)
Divide students into groups of 2-4 and make a copy of the student lab directions for each student to put in their science notebook. Adjust the lab directions as needed for the level of your students. For maximum inquiry, give fewer directions.

Prepare materials for the lab according to the teacher directions provided.

During the lab, check with each group, listening for their ideas and thoughts and guiding them past misconceptions.

Part 1A: Students make water waves in a sealed jar. They discuss as a group, write procedure and observations, and draw pictures. They discuss what happened and write an explanation in their science notebooks.

Part 1B: Students make water waves in a plastic tub, aquarium, or baking dish. They discuss as a group, write procedure and observations, and draw pictures. They discuss what happened and write an explanation. They compare Part 1A and Part1B as a group and design a graphic to show the comparison. At this point choose to have a large group share/discussion, writing the explanations from each group on the board/overhead, or do all three parts and then have a discussion.

Part 2: Students make waves and observe the motion of an object in and on the water. They discuss as a group, write procedure and observations, and draw pictures. They discuss what happened and write an explanation in their science notebook. After they finish Part 2, they are asked to think about this question: How does wave motion determine the time it takes for an object to move from point A to point B on the ocean?

Explanation​

10 Minutes

At the end of the lab, bring the class together for large group discussion of the questions “How does wave motion determine the time it takes for an object to move from point A to point B on the ocean?” The class should arrive at the conclusion that a wave is energy moving through the water, but the water particles only move in a circle. This means that an object on the water does not move because of the wave energy. Have students write the conclusion in their science notebooks.

Elaboration​

1 hour

This next activity expands on the idea that winds cause the surface currents and starts to challenge and extend the students’ conceptual understanding. Until this point students know that weather systems with defined wind patterns create the surface ocean currents. This activity adds a level of complexity with transient weather systems producing winds in opposition to the “normal” currents that the students have already discovered. Students will be asked to test their knowledge and understanding of what creates the currents.

Divide the students into pairs or groups. They will role-play the captains of a cargo ship about to leave from Seattle, Washington, headed to the port of Anchorage, Alaska.

Background:
More than 98% of cargo shipped to and from the United States is transported by water. Students should realize that despite the prevalence of air travel and advances in aerospace technology, the earth’s oceans are still vital to freight transportation, energy production, and recreation (NOAA 2008). The port of Anchorage is the most active port in Alaska through which more than 95% of all cargo entering and leaving Alaska passes, acting as a distribution center of goods to the rest of Alaska. It serves 80% of Alaska’s population and 90% of the consumer goods entering Alaska.

The scenario:

• The goal is get to the port of Anchorage as quickly as possible; each captain is paid by how quickly they get their cargo to the port of Anchorage.
• There are currently two weather systems impacting the route, a high pressure system over the Gulf of Alaska, and a low pressure system over Bristol Bay.

Assignment: Develop the quickest route to Anchorage.

Distribute the map to have students plot their ship’s course.

Things to keep in mind:

• Students should assume that a straight line is the quickest path (disregard rhumb lines and the Great Circle methods) to get between two points with still water.
• Students should use their knowledge of the average circulation in the Gulf of Alaska (students should use their maps in their science notebooks) in this exercise.
• Students might consider how the “normal” current might be affected with the storm.
• Seattle, Washington, and Anchorage, Alaska, are 2,327 kilometers apart.

The following feedback can be offered to the students and proposed as questions to answer in their science notebooks:
Most students will direct their ship between the low and the high pressure systems where there is a direct current north into Anchorage. Probe the students to see if they understand that this route is directly opposed to the “normal” current that the Gulf of Alaska gyre produces.

Possible discussion/analysis questions could revolve around:

How much can a single weather system affect the Gulf of Alaska gyre?
How long would the weather system have to be there to direct the water against the normal current?
Which side of Kodiak Island might be quicker?
How do the magnitudes of the winds associated with the weather systems compare to the speeds of the current in the gyre?
Based on the students’ reasons for their proposed ship route, do they think it would take longer to complete the northbound trip or the southbound trip?
There isn’t necessarily a right or wrong answer to this scenario. Evaluation of this exercise hinges on the extent to which the students can justify their route.

Evaluation

Evaluation takes the form of a classroom discussion that immediately follows the ship route exercise above, allowing formative assessment of student knowledge and understanding about how weather determines surface currents.
A Socratic Seminar format would be well suited to this discussion. The questions don’t necessarily have right or wrong answers but rather encourage divergent solutions with logical arguments.
The following questions can guide the seminar/discussion and lead into the investigations that follow:
Based on all knowledge and understandings to date of weather systems and their effects on surface ocean currents, why and how did many of the toys wash ashore in Southeast Alaska?
If the toys all spilled in the same location, how did some of the toys wash up thousands of ocean miles away from other toys?
What further information would you like to know about the spill and time period following the spill, to better ascertain the route the toys took through the Gulf of Alaska and beyond?
Possible Answers:
The weather on the day of the spill and the weeks and months following it.
Gulf of Alaska buoy data during the time the toys were afloat.
How fast do the toys move in response to a given wind speed?

Extensions

Local Expert. Bring science into your classroom by inviting a local meteorologist to talk to the students about their job of forecasting, weather patterns in Alaska, and how they use technology to do their job. In Alaska there are National Weather Service offices with meteorologists in Anchorage, Fairbanks, Juneau, Annette, Barrow, Bethel, Cold Bay, King Salmon, Kodiak, Kotzebue, McGrath, Nome, St. Paul, Valdez, and Yakutat. If a visit is not possible, it might be possible to bring the scientist into your classroom with Skype software. Skype allows you to “call” another person computer-to-computer and have a conversation replete with audio and video free over the Internet. It is available as a free download on the Internet and is used to network with anyone else who also has Skype free of charge.

Quikscat Images. A possible sidebar activity with a foray into technology would be to explore QUIKSCAT data, showing current satellite-derived ocean surface winds. QUIKSCAT images are derived from an instrument called a scatterometer, mounted on polar orbiting satellites that calculate wind speed and directions based on ocean surface roughness algorithms. You can use an archived image if you don’t have Internet access.
Do the winds from the QuikScat image match well with the ocean currents the students sketched in their science notebooks? If so, why? If not, why not?

Coriolis Effect. Examine the Coriolis Effect, which is responsible for the “spin” of a weather system. You might also want to use a lesson plan for a hands-on activity.

Curricular Connections

This investigation can provides connections to math through graphing activities and measurements and calculations of wave frequencies and periods. The many opportunities to write, discuss, and present information to the class provide connections to language arts.

Ideas for adapting to different local environment or context. Investigate local cultural traditions and knowledge related to tides.