The Force of Water

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SWBAT describe the force of water .

Big Idea

Water is a powerful force that can destroy man-made structures!

Teacher Preparation

In this unit, students have become familiar with push and pull forces that they can see and manipulate, like pushing a wooden block or a chair and pulling a plastic cup with a piece of yarn attached to it. Now, we are moving on to experiment with unseen forces which supports the Essential Standard 1.P.1.2., "Explain how some forces (pushes and pulls) can be used to make things move without touching them, such as magnets". Click here to hear why I teach the Essential Standards.

The force of water causes many natural occurrences, including erosion and floods. The power of water has been harnessed by man made structures, from a simple waterwheel turning a mill to water powering a hydroelectic powerplant. Although these uses of water are not necessarily just a push or a pull, they are certainly a force, which is my rational for including both water and air forces in this unit.

For this lesson, I use:

Student journals

Source of water such as water hose or several watering cans

Stackable objects, such as pennies, plastic or wooden blocks, plastic cups, etc.


Warm Up

10 minutes

To get students really excited about the force of water, I start this lesson with a video of myself at Niagara Falls (turn the volume up to hear the roar!!). Here is another example. Then, I show them some pictures of Niagara Falls, and other things that have been created by the force of water - the Grand Canyon was carved by the Colorado River, caverns created underwater, and the Tianzi Mountain which were once carved underwater but now stand tall above ocean level (picture to the right). After sharing the pictures, I say,

"Water is a powerful thing but we can forget that easily because we use it every day. Today, we are going to experiment with water as a powerful force like Niagra Falls. The amount of water that goes over Niagara Falls in one minute is equal to one million bathtubs! Now, you are going to try to build a structure that can stand up to the force of water."


25 minutes

To guide the structure of this lesson, I use the engineering design cycle that I introduced in this lesson. As I write 'The Force of Water' on the board, I say,

"Boys and girls, meet me on the carpet with your science journal and a pencil. Turn to a new page and put the data and the title which is 'The Force of Water'."

 When students are settled on the carpet, I direct their attention to our design cycle poster and review the steps of the cycle with them quickly, saying,

"First, we think about the problem or question we have. Then, we plan two solutions or experiments to help us solve the problem or answer the question. After that, we invent or build what we planned. When we have completed the building, we evaluate what we did and then finally we communicate the results. So, for today, we want to find out what kind of force water has on objects and how it can move things. How could we ask that as a question?"

After we listen to a few suggestions, we settle on a question like 'How does the force of water create motion?' or 'What kind of motion can water create?' This supports the Science and Engineering Practice 1, asking questions that can be answered by investigations. This also ties directly into the Essential Science Standard for predicting forces, because students will build a structure, make a prediction, and then pour water on it to see what motion is created. The heavier and studier their structure is, the more force they will need to create with the water to get the structure to move. The lighter the structure is, the faster it will move!

 To start students along the design cycle as I model in my own science journal, I say,

"In your notebook, let's make the design cycle more organized today. We are going to work from the top of our page to the bottom instead of trying to fit our work in little circles. Near the top of your page, write 'Question', like mine, and then write 'How does the force of water create motion?' Then, we are ready for step two. Who remembers what the second step is?"

As we work through the design cycle, I continue to record all of the information in my own journal to model the correct way to do it and to also provide a visual guide for students who may need one.

"That's right, we need to make 2 different plans. Today, you are going to work with a partner of your choice and design two structures, or buildings, to test. Here are the materials you can choose to work with. Talk with your partner and draw two different structures you could build to test the power of water by pouring water on top to see if they move. You have five minutes, so talk and draw quickly!"

It is important to articulate to students which materials they can use before they start their design. The focus of this lesson is on the force of water - not on designing a tower - so I prepare the materials ahead of time and select it for the students. This is an easy experiment for them to replicate at home so I know they will try other materials, too!

Also, before class, I create a document and list each set of partners and display it on the Smart Board (you could also just do this on poster board or your whiteboard).

I include a time limit for each step of the cycle. This keeps us moving along the lesson and minimizes any arguments between students or off task behavior, because they feel the pressure to finish their assignment. If I notice that students are not working quickly, I will use a timer on my Smart Board to help students track their time.

As students talk and draw their plans, I walk around and ask students how they are going to build their structures and what they think will happen when we pour water onto them. Students are collaboratively planning their investigation which supports Science and Engineering Practice 3. As students finish their plans, I say,

"Now that your plans are finished, you are going to choose with your partner which plan you think you would like to try. Quickly talk about it and choose one - you have 30 seconds, go!"

After students have chosen their plan, I let partners pick up their materials and begin constructing their design. As they work, I walk around and remind them that they need to carefully follow their design so that I can tell from their drawing what their structure should look like. As students finish, I invite them to test their design either in the sink or outside. When we take the designs outside, we first use the watering can with very light pressure so that not much happens, then I use the watering hose and apply lots of pressure. As each group watches the other structures, I start to ask the group what they think will happen as more force is applied from the water. This encourages students to predict the motion of an applied force, supporting Essential Standard 1.P.1.3.


Wrap Up

10 minutes

As students predict and watch what happens as the structures are tested against the force of water, I begin to have the conversation with them about how this investigation is like the pictures we saw of Niagara Falls and the caverns. The force of the water can crush things like a waterfall or carve things like caverns. After we finish the investigation and return inside and dry off, we gather at the carpet with our journals again. I say,

"The next step of the design cycle is to evaluate your design. Take 2 minutes with your partner and draw a super-quick picture of what happened in your journal, and write a sentence or two about what happened."

After about 2 minutes, I say,

"What did you notice about the structures and the power of water?"

As students make observations and recount their experiences, I take notes on chart paper. These will be used in tomorrow's lesson where students will find out how water can carve caverns and rivers through force.

I also ask students,

"If you had to do this again and design a structure that could last in the force of a waterfall, what would you do the same and what would you change? As we talk, if you hear a good idea, write it in your journal. That way, you can try it out later".

As we finish this lesson, I say,

"We have already finished the final part of the design cycle! We have communicated our results and our findings to each other. When you communicate things and you talk and share what you learned, it is important to listen to other people. Why might that be?"

At this point, it is important to articulate with students why teamwork and collaboration is important in science - we find out more, share ideas, and improve our work through sharing and communicating. To finish the lesson, I say,

"Tomorrow, we are going to work with water again but instead of investigating the force of water moving down like a waterfall, we are going to look at what happens when water moves across land".


After today's lesson, I pick up the journals and check the student's design cycles taking notes on my journal check in sheet. I look to see who is correctly labeling the parts of the cycle and who is completing their work. It is important that students record their plan for their designs, so I check that they have 2 designs drawn and then their evaluation of what happened.

During the lesson, I asked them to draw a quick picture of the outcome and add a sentence or two. I check to make sure that students are beginning to understand that scientists record their work so that they can return to it later in order to make improvements. If I notice any students are not utilizing their journal in this manner, I will make a note to work specifically with them in tomorrow's lesson.