This super easy salt water experiment is the perfect science activity to teach kids about the density of salt and fresh water. Great hands-on science experiment for teaching an ocean unit!
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With summer approaching and beach trips planned it’s the perfect time to learn about the ocean! I designed an easy salt water experiment for kids to show them how the salty ocean water is different from fresh river water. At the end of this post you will find 20 more ocean-themed learning activities to do with the kids!
Salt Water Experiment
I was so excited to learn about the ocean with my kids! There are so many crazy animals and undiscovered areas of the ocean that I just find fascinating.
Before doing our science experiment we took some time to watch the two episodes about ocean life on Planet Earth. (If you haven’t seen these AMAZING wildlife documentaries you are missing out! Check out these DVDs from the library or get them from Amazon ASAP!)
Once we had some solid background knowledge about the ocean we set up our salt water experiment. This was the first time I introduced the kids to a “controlled variable”. (The thing you don’t change so you can compare other things to it.) My little scientists are growing up.
Small plastic jewels (We purchased ours at the dollar store. If you don’t have these exact jewels, don’t worry. You can use raw eggs or small grapes instead. I did a similar Halloween-themed salt water experiment that you can see here.)
Several clear cups full of water
*Feel free to test other substances like washing soda, baking powder, sand, cornstarch, etc. It’s always fun to experiment to see what happens!
- Dissolve 2 tablespoons of salt in one cup, 2 tablespoons of sugar in another cup, and 2 tablespoons of baking soda in a third cup. Be sure to leave one cup as plain, fresh water. (This is your controlled variable.)
- Label each cup so you keep everything straight.
- Have the kids think about what might happen when they drop the jewels into each cup. Will the jewels sink or float?
- Drop the jewels into each cup to find if the kids’ guesses were correct!
*Hint: You may need to add more salt/sugar/baking soda to the water, depending on what kind of jewels or food you are using in this experiment. Add enough that you can see some extra powder on the bottom of the cup. The salt water and baking soda water should make the jewels float. Read below to find out why!
The Science of the Salt Water Experiment
When you add salt to water it makes the water more dense. This means it gets heavier. Many objects that sink in fresh water will float in salt water!
Objects float in baking soda water because baking soda is a kind of salt. It dissolves in water to make the water more dense, just like table salt does. However, baking soda has another property that gave us a little bit of a surprise!
When baking soda dissolves in water some of it reacts to form carbon dioxide gas. If you look carefully you will see tiny bubbles rising from the bottom of the cup. We must have added just the right amount of baking soda to the water because when we put the jewels in the cup they hovered right in the middle! Over time the tiny carbon dioxide bubbles attached to the plastic jewels and acted like tiny life preservers, carrying the jewels to the top of the cup. It was absolutely FASCINATING to watch that process! My son loved watching the jewels slowly rise to the surface.
Give this fun and easy science experiment a try while you learn about the ocean this year! And be sure to check out the list below for more ocean-themed activities from some of the most creative bloggers you’ll ever find.
FROM LEFT TO RIGHT:
(NOT SHOWN) Ocean Size Sort: Small, Medium and Large // Liz’s Early Learning Spot
Odd and Even Number Fishing // Adventures of Adam
Ocean Animal Beginning Sound Clip Cards // The Letters of Literacy
Ocean Counting Mats // Mom Inspired Life
Ocean Felt Busy Box // Teach Me Mommy
Free Ocean Flip Books for All Ages // Simple Learning Kids
Shark Roll and Cover Game // Playdough to Plato
Octonauts Hermit Reef Oil Spill // Tuff Spot Play
Write and Wipe Addition Cards // The STEM Laboratory
DIY Ocean Counting Clip Cards // Life Over Cs
Ocean Sensory Bottle // The Pleasantest Thing
Salt Water Experiment | Ocean Science for Kids // Science Kiddo
Ocean Animal Count and Clip Cards // The Kindergarten Connection
Ocean I Spy Printable // Powerful Mothering
Ocean Sensory Bin // Play & Learn Everyday