What Do Caves and Oceans Have in Common?

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SWBAT demonstrate how water can dissolve some minerals.

Big Idea

Students explore how water dissolves minerals, creating caves or salty bodies of water.

NGSS Connections and Class Preparation

30 minutes

This lesson helps develop students' schema on water erosion in order to address the anchor question "How can people prevent or slow down wind or water from shaping the land?"

Through the act of discovery, following scientific practices, students synthesize this lab with supporting information, to create meaning for themselves.

The activity I am using is adopted from: Hands-On Earth Science Activities by Marvin N. Tolman (image)

NGSS Standards

ESS! - Make observations from media to construct an evidence-based account that Earth events can occur quickly or slowly. 

Through observations via experimentation, students start to build a schema that Earth events, salty oceans and caves occur slowly.

ESS2 - Wind and water can change the shape of the land.

Through experimentation, students learn how moving water can dissolve and transport minerals, creating limestone caves and salty oceans.

Science Practices - Appendix F

- Planning and Carrying Investigations (SP 3)

Students set up an experiment to observe how moving water interacts with limestone and rock salt.

- Analyzing and interpreting Data (SP 4)

Teams review and share their observations to interpret how water makes caves and oceans salty.

Cross-cutting Concepts - Appendix G

- Cause and Effect  (XC 2)

Students observe the effect of running water over limestone and rock salt. These observations are used to learn how some caves are formed and where most salt comes from in the oceans.


small pieces of limestone (check the local nursery, mason, or order on line); A local mason gave me sample pieces of limestone which I broke into smaller pieces

small water bottles with lids; one / team (river channel)

rock salt

clear plastic container, the size of a butter margarine container (catch basin)

basters; one / team (used to send water down the river channel)

magnifying lenses

rainwater (or use tap water with added vinegar, to make it acidic)

containers for rainwater; one / table

small tubs (for the catch basin and river channel)

rubberbands (to prop up the river channel)

Lab Prep

use a nail and poke holes in the water bottle lids

cut the bottom part of the water bottle off and save

break the limestone into small pieces

rinse the limestone with water

fill six small water bottles with rock salt and 6 with limestone (remember to place the lid on)

insert the bottom back onto the bottles

copy the lab booklet; one book / student 

The lab booklets are set up for rock salt or limestone since half the teams will be testing either rock salt or limestone. I set up teams so that a rock salt group sat across from a limestone group.

I chose to have each student write in a lab book to hold the individual accountable and to encourage him or her to be involved in all aspects of the lab. Students still performed the lab with a partner and discussed the lab.

fill 6 containers with water for teams to use

Lab Material for Each Team

water bottle with limestone pieces or rock salt




magnifying lens


Question for the Day

5 minutes

I start science with a question, usually written on the board.  This provides an opportunity for  students to consider today's topic before the lesson has officially begun. 

Students know when they return from lunch, we meet on the rug to read our 'science question for the day'. I have established this routine with the kiddos to keep transition time short and effective and redirect student's attention back to content while allowing time for focused peer interaction.

Question for the Day: How does flowing water make some caves and oceans salty? 

This is the question that I will use next time I do the lesson. I used the question below, but I did not feel like it connected to the lab as directly.

Question for the Day: How are some caves and oceans alike? I have pictures of caves and oceans next to the question.

Students read the question with me and then turn to a neighbor to discuss. After a couple of minutes, I signal for the kiddos' attention and call on volunteers to share their ideas.

I explain that they will be doing an experiment to see how running water, such as in a river or when rainwater flows down a mountain, could make oceans salty or caves.

I use the random sorter to make 12 teams. 6 teams will be using limestone and the other 6 will be using rock salt.

After I project the teams, I direct students to sit with their team member at their desks.

Lab - Hypothesis to Observations

30 minutes

While teams organize their work space, I pass out the lab books, samples of limestone or rock salt and magnifying lenses.

I have set up the lab book so that students are working on one step of the scientific process at a time. This helps my students who can feel overwhelmed when seeing a lot of print at one time. It also helps to pace the lesson and to keep the students on the 'same page'.

I direct the teams to read the question and examine the rock salt or limestone under the magnifying lens. I encourage the students to discuss their ideas before writing their hypothesis. 

After a couple of minutes, I signal for their attention. 

I explain why they are testing limestone and rock salt. "Limestone is a common rock found in most regions of the world.

Rock salt has sodium which is a mineral found in granite, another common rock. So scientists, we can use the rock salt and limestone as our model of a mountain."

I do not want to get too much into the chemistry, so I may say that salt is a common mineral found in most rocks. Between you and I, I chose these 2 materials too because they will noticeably dissolve with water which the students can observe in one lab (or over a week if you allow the water to evaporate so students can see what was left behind). I don't say anything about the material dissolving as I want the students to discover this for themselves.

Discuss with your partner what you may want to write for your hypothesis. Remember to include your reason for your hypothesis."

"Think about any previous learning, observations or experiences you have had that may help you write your hypothesis, be sure to share this with your partner."

I check that teams have their hypothesis written, then review the materials and procedure with the students.

"If you want to find out what happens when water flows over rocks, limestone, or minerals, such as rock salt, then we will need to..." I call on a volunteer to complete the sentence. 

"Where or why would water be flowing over the Earth? Right, when it rains and water is flowing down a mountain, or a river. So in our lab today, we will make a model of a river to see if we can find out what happens when water flows down a mountain."

"I will show you how to set up your lab, as I do, you will make a diagram for the lab set up on this page."

I show them the diagram page in their lab. As I demonstrate how to set up the lab, I model how to draw the diagram.

I explain how their diagram is like a model of a mountain side and the limestone or rock salt are some of the common rocks and minerals found on Earth. 

I want them to make a diagram of the lab so that I can scaffold how the lab model is used to represent part of a river system, the slope is like the side of the mountain with water flowing down it like in a river.

After students draw their diagrams,  I read the procedure page with them. Next I review the 2 observation pages.

"Some observations you will do today, and other observations you will do next week after the water starts to evaporate."

"For the observation page you will fill out today, remember to write your observations about the water and rock salt or limestone before you pour water down the 'channel."

After questions have been answered, I direct one student from each team to pick up their materials. Teams check off their materials on the material page. 

The remaining time is used to conduct the lab and for teams to write their observations. I circulate around the room to assist with setting up the labs. 

Some teams may need help from others to set up their 'river channel'.

Lab Wrap - Results and Conclusion to Clean Up

25 minutes

After teams complete their observations, I direct students to meet me on the rug with their lab booklet, pencil and clip board.

I move teams from the lab station so that they will not be distracted by the materials.

"Scientists, now that you have tested and observed what water does to limestone or rock salt, you are ready to summarize your observations in complete sentences when you write your results."

I project the observation page and show the students how they can use the 'before' and 'after' observation phrases to help them start their result sentences.

"I could start my sentence with this phrase, Before the water moved down the channel the limestone looked .... and the water looked ...." I write these sentence frames on the board.

"Your observations will help you write your results."

Teams return to their tables to review their observations and then write their results in lab booklet.

When I see that most students have completed writing, volunteers read their results. I direct students to listen for the before and after descriptions.

"Let's hear from a limestone group. What were your results?" I call on a rock salt group to share next.

Next I ask the class what they learned from this lab. I write student responses on the board which I will transfer later to the  KLEWS chart.

I write their responses on the board versus the KLEWS chart, because I want the students to be able to access this information easily when they write their conclusion.

"These are some great thoughts, which can be used when you write your conclusion."

Before students start their conclusion, I connect the lab simulation to real earth events.

"In places where there is limestone, water can trickle down through the limestone, dissolving the stone. Over thousand and thousands of years with enough water trickling through in the same places a cave is formed, because the water dissolved the limestone in that spot."

"So how are limestone caves and oceans alike? Think about what you learned with the water? Moving water dissolves the limestone to make a cave dissolves rock and carries it to oceans."

"So you have a lot of information that you can include in your conclusion."

"On the conclusion page you will write whether your hypothesis was correct and why. You may want to use the information you learned from your team or our class discussions to help explain your reasoning."

When you write about what else do you wonder or what other questions you have, you could write about any other experiments or questions you may have about how water affects land."

As teams complete their conclusion, I carefully move the 'catch basins' to an 'observation station'.

When teams complete their conclusions, I show the class where the catch basins are so that they can take observations over the next couple of days as the water evaporates.

Students place the lab materials on the back table and their lab booklet in their science folder.