Float or Sink? Salt Water or Fresh Water?

What sinks? What floats? What is salt water and where do we find it? What effect does salt water have on objects? What happens when Fresh and Salt water meet?

On a very rainy March morning, we decided to tackle these good questions! On Day 9 of the Mother Goose Time unit, “Down at the Pond”, we were learning all about Floating Pond Plants. We set up a simple Sink/Float station, and then took it a step further for our older friends. Would the introduction of Salt to the water change the results? In both measuring cups we had 1 2/3 cup fresh water. We added 1/3 cup of salt to one of the measuring cups and stirred until it was dissolved. Then we tested each item, first in the fresh water and then the salty to see if the results were the same or different.17156142_1318067818284181_379047564054723541_n Then we moved on to the egg test. First we made a hypothesis, based on the Sink/Float station, about what we thought would happen to the egg placed in the fresh water versus the egg in the salt water.  The measurements of water and salt were the same as before. The egg placed in the fresh water sunk, and the eggs placed in the salt water floated!

17103794_1318067801617516_4128197596339231014_nNow, what happens when Fresh water and Salt water meet? Our Preschool and Pre-K friends have been learning all about the Water cycle and different bodies of water during our Pond unit. Rivers and Streams flow to the ocean as part of the water cycle. We started out with the same measurements, but this time we added some food coloring and used an eye-dropper to slowly add salt water to the fresh. The Salt water sunk to the bottom, or maybe it made the fresh water float. (The separation was very slow, which is hard for preschool, so we left it sitting on the counter and we will revisit later, but this photo is mid-process.)


Most kids enjoy science, but a number of our students learn best through these types of activities. They really need to test their theories and see what happens, in order to make the connection. These experiments were a fun way to demonstrate the differences between salt and fresh water properties and it was a great expansion to the Sink or Float activity from Day 9.

*Experiment ideas courtesy of Little Bins for Little Hands


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