Ocean science for kids: Salt water and waves

If you have been following along, you know that my kids and I recently completed a preschool ocean unit to learn all about the ocean and the animals that live there. As part of our ocean unit, I wanted to introduce the kids to some ocean science focused on sea water. Specifically, I wanted them to learn a little bit about the properties of salt water and about the power of waves. This post details a variety of ocean science activities we did to learn explore these two topics.

Note: For more resources, printables and activities related to the ocean and its inhabitants, please see my ocean unit study page.

The goals for these ocean science activities for were for my kids to:

• know that oceans cover most of our planet
• understand the difference between salt water in the ocean and fresh water we drink
• learn what causes waves
• learn how waves break down rocks and other objects over time

Oceans cover most of our planet

We started by pulling down our globe. I showed the kids how most of the globe was covered with oceans rather than land. (At this point I was wishing we had a more traditional globe where the oceans were blue instead of off-white.)

Then we played a game where the kids closed their eyes while I spun the globe. With their eyes closed, they had to put out their index finger until they touched the globe. At that point, they opened up their eyes to see if they had landed on land or water. If you do this several times, you should find that your kids’ fingers hit water more than on land. With older kids you could even make a chart showing how often they touched land vs. water.

Ocean water is salty

Next, I wanted the kids to understand that ocean water, unlike the water we drink, is salty. I filled two containers with 4 cups of water.

Then the kids dumped an entire shaker of salt into one of the containers.

They stirred until the salt dissolved into the water. (“Look mom, the salt is disappearing!”)

Then I had the kids taste both the fresh water and the salt water. To say that QBoy was not a fan of the salt water would be an understatement. XGirl, on the other, seemed to really like the salt water and kept asking for more tastes! 🙂

We talked about how ocean water is salty but the water we drink everyday is not.

Ocean water is more dense than fresh water

Next, I wanted to demonstrate the fact that salt water is denser than fresh water. Realizing the containers I had been using were shorter than ideal for the next demonstration, I poured the fresh water into a tall, narrow container instead. Then the kids placed a hard boiled egg in the water and we watched as it sank to the bottom.

Next, I poured out the fresh water and filled the container with salt water instead. The kids put the egg back in, and this time they watched as it floated! (Note, you need to add quite a bit of salt to the water to get the egg to float. Without enough salt, the water will not be dense enough and this demonstration will not work.)

Learning about waves

To teach the kids about ocean waves, I decided to have them each make their own ocean in a bottle. They used a funnel to pour some sand into their bottles.

Then they added water.

Next, we put the caps on tightly, and laid the bottles on their sides so the kids could see the sand layer underneath and the ocean water layer on top.

Then the shaking ensued. Because really, what kid doesn’t like to shake things, especially bottles with liquid inside? 🙂

Waves break down and polish rocks and other objects

The kids and I talked about how waves are caused by wind. We also talked about how sand is formed when waves break rocks in to tiny little pieces over time. This discussion gave us an idea!

I grabbed some sea glass and showed the kids how this glass was polished from years of waves washing over it, knocking it against other objects, and making it smooth.

To further illustrate the point, we took a hammer and smashed the sea glass into small pieces. The kids were able to look at the smashed glass in the baggie and see how it had hard sharp edges.

We continued to discuss how the ocean waves could make the glass smooth again by slowly polishing them over time. At that point, we decided to drop some of the broken sea glass pieces into their bottles so they could make waves to polish the sea glass again.

So they dropped their pieces in and began shaking. Of course, they were a little disappointed to hear that it would take more than a few minutes of shaking to polish the sea glass. In fact, a LOT more than a few minutes. 🙂 But it was still fun to shake the bottles, so they didn’t seem to mind too much.

But to further illustrate the point that waves and sand polish the glass over time, I pulled out some sand paper and cut it into strips for the kids. I showed them how the sand paper was covered with sand, just like the sand from the ocean.  They then began rubbing some sea glass on the sand paper to polish it.

More resources for learning about the ocean

More ocean posts from Gift of Curiosity:

• Ocean Montessori activities
• Learning about ocean animals
• Shell activities
• Blubber experiment
• Ocean animals book & 3-part cards
• Ocean Printables Pack
• Ocean Do-a-Dot Printables
• Ocean I Spy

For more resources, printables and activities related to the ocean and its inhabitants, please see my Ocean Unit Study page and my Oceans Pinterest board.