Water Cycle & Salinity

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Objective

SWBAT identify the relationship between salinity and latitude | SWBAT diagram the steps of the water cycle and define each of the major steps

Big Idea

In this introductory lesson to Unit VII, students explore the relationship between salinity and latitude before jumping into a brief synopsis of the water cycle. They then use "scenario cards" to apply the steps of the water cycle to some real-world scenar

Lesson Introduction

This lesson is the first in Unit 7, in which students learn all about the features and machinations on Earth's surface. We start the unit with one of the most fundamental concepts, and one in which students have probably had prior exposure to - the water cycle. This lesson involves a brief recap of the vocabulary and phases of the water cycle, while also addressing the relationship between salinity and latitude. Students have the opportunity read brief "scenario cards" to practice identifying and applying the steps of the water cycle to novel problems. As a final note, there are no special materials or equipment needed for this lesson save for the provided and attached resources below.

[Note: For embedded comments, checks for understanding (CFUs), and key additional information on transitions and key parts of the lesson not necessarily included in the below narrative, please go to the comments in the following document: 7.1 - Salinity & Water Cycle (Entire Lesson w/comments). Additionally, if you would like all of the resources together in a PDF document, that can be accessed as a complete resource here: 7.1 - Salinity & Water Cycle (Entire Lesson)[PDF]. Finally, students may need their Earth Science Reference Tables [ESRT] for parts of the lesson (a document used widely in the New York State Earth Science Regents course) as well.]

 

Do Now

10 minutes

Students come in silently and complete the (attached) Do Now. In this case, the Do Now is a review of material and some "hot standards" from the previous unit in Meteorology. After time expires (anywhere from 2-4 minutes depending on the type of Do Now and number of questions), we collectively go over the responses (usually involving a series of cold calls and/or volunteers), before I call on a student and ask them to read the objective out loud to start the lesson. 

As a general note, the Do Now serves a few purposes:

  1. It serves as a general review of the previous day's material;
  2. It is a re-activation of student knowledge to get them back into "student mode" and get them thinking about science after transitioning from another content area or alternate class;
  3. as a strategy for reviewing material students have struggled with (for example, using this as a focused review for material that they have struggled with on unit assessments or recent quizzes); and,
  4. It is an efficient and established routine for entering the classroom that is repeated each day with fidelity (I never let students enter the classroom talking. While it may seem potentially severe to have students enter silently each day, this is both a school wide expectation and a key component of my classroom. In many respects, I find that students readily enjoy the focus that starting with a quiet classrooms brings each day).

Salinity & Latitude

10 minutes

We start the first lesson with a brief synopsis of the relationship between Salinity & Latitude. Since, in the last unit, we had the opportunity to learn holistically about the climate of Earth and how the ocean currents have an effect on them, I wanted to start this unit off in a similar vein. The lesson itself begins when I ask students to look at and infer the relationship between salinity and latitude based on the graph. 

In each of my classes, I had many students make attempts outright, but none seemed to have the answer. So, in scaffolding down, we looked at where the salinity was highest (roughly 25 degrees N/S latitudes) and lowest (the Equator and closer to the higher latitudes). In thinking about this, I pointed them to the climate belt diagram(s) on Page 14 of their ESRT. This shows that there are relatively high amounts of precipitation around the Equator and 60 degrees N/S latitudes. Once students saw this, they were able to infer that the increased rainfall dilutes the ocean water around those latitudes, dropping the water's salinity. The opposite is true around 25 degrees N/S latitude, as the area of high pressure leads to relatively low levels of rain, which concentrates the water's salinity around those latitudes.

Water Cycle & Vocabulary

10 minutes

The next section serves as an introduction to the vocabulary of the water cycle. Throughout the course, we've been using some of these words regularly, but in terms of completing the loop on the all of the requisite steps of the water cycle, we define them all here. In relation to the Water Cycle & Vocabulary resource, I first start out by asking: "What's the thing that drives this entire process?" As we learned in the last unit, most of the Sun's energy goes to evaporating water from Earth's oceans, so the Sun is the ultimate driver of the water cycle. Starting with evaporation (when water enters its gaseous phase), we go through all of the other steps in the resource until we get to precipitation (when water falls from the atmosphere toward the ground). Additionally, after defining the actual terms, we annotate (I have the same image on my document camera at the front of the room) the arrows with the appropriate definition. 

Water Stories

25 minutes

For whatever reason, my students really enjoy this section of the lesson on Water Story Cards. To note, like the other parts of the lesson, this is also relatively self-explanatory. It isn't necessarily Regents-based (like most of my other lessons) in its practice component, but it does ask students to utilize their newly formed vocabulary and water cycle content knowledge to these novel, "real world" scenarios (Here are a few photos I snapped: Water Story Cards IIWater Story Cards III). There are about six (6) water stories, each with a particular set of questions after posing a brief scenario. While some of them are fairly straightforward, there are a few tricky questions in there that might stump a few of your students. I generally let them work together on this (as evidenced here and here). (Note: the time allotted in this section isn't what they'll need to finish, but also accounts for the time for you to collectively review all of their answers and responses.)

Exit Ticket & Closing

5 minutes

In the last few minutes of class, I have students complete the daily Exit Ticket. For the sake of time, I have students grade them communally, with a key emphasis on particular questions and items that hit on the key ideas of the lesson (Note: This usually manifests as students self-grading, or having students do a "trade and grade" with their table partners). After students grade their exit tickets, they usually pass them in (so that I can analyze them) and track their exit ticket scores on a unit Exit Ticket Tracker. 

After students take a few seconds to track their scores, we usually wrap up in a similar way. I give students time to pack up their belongings, and I end the class at the objective, which is posted on the whiteboard, and ask students two questions:

  • Do you feel that you mastered the objective for the day?
  • Can you reiterate one thing you learned about (in this case, information on the steps of the water cycle, etc.)?

Once I take 2-3 individual responses (sometimes I'll ask for a binary "thumbs up/thumbs down" or something similar), I have students leave once the bell rings.