Salt Water Density Experiment
How does food coloring react to salt & fresh water?
We love experiments that are no fuss and easy! Paired with our FREE observation lab sheet, how can you go wrong! Your students get to predict what they think will happen, make observations, and then conclude why. This experiment uses simple kitchen items to mesmerize your students. We use this Salt Water Density Experiment while investigating our Earth’s Water Unit since it is an effective at displaying the difference in density between salt and fresh water.
*Don’t miss our Floating Egg Experiment with FREE lab sheets that also investigates the difference in density between fresh and salt water. Wait… there’s more! Discover how the freezing point of salt water and fresh water differ in this experiment, “Does Fresh or Salt water freeze faster?”
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Important Terms and Facts to Introduce
Before conducting the experiment, there are a few things you should cover with your students to create a meaningful learning experience. First, spend time talking about the terms below. We discuss the meaning of salinity and density amongst other terms.
– Density is the amount of mass in a given volume.
– Salt is also called Sodium Chloride.
– Salinity describes the amount of salt dissolved in water. Saline water is water with salt dissolved in it.
– Solution is a type of homogeneous mixture composed of two or more substances.
– Solute is a substance dissolved in another substance, known as a solvent.
– Water’s density is 1 g/ml.
Salt Water Density Experiment Observation Sheet
The Salt Water Density Experiment Observation Sheet will guide your students through predictions, observations, and give students a place to write a conclusion. Teacher will need to guide student through the experiment and science explanation.
Gather Materials
The materials list is likely to be found within your kitchen. You will need 2 clear glasses, water, salt, and food coloring. Yes, that is it!
Salt Water Density Experiment Lab Procedures
Make Predictions
We started by filling both glasses up with about 1 1/2 cups of water. To create salt water, we added 2 tablespoons of salt to one of the glasses and stirred until completely dissolved.
Next, the students made their predictions about what they thought would happen when we added the food coloring to each glass. One of mine thought that the fresh water would be lighter in color while the salt water would be darker. Two other students predicted that the food coloring would produce bubbles in the salt water.
Make Observations
The first glass we put food coloring into was the fresh water. We only put 3 drops of blue food coloring in. There is no need to stir. This is the optimum time to just observe and then draw your observations. You will notice that the food coloring drops went to the bottom of the glass.
Next, we added the drops of food coloring to the salt water. As you can tell from the next photo, it immediately stopped when it hit the saline solution. It stayed in a layer above the salt water.
Draw Conclusions
the kids and I talk about why they think the food coloring reacted the way it did. In the end, we discuss how salt added mass to the density of the water causing it to become more dense. The density of water is a little less than 1 g/ml. So, if something sinks in water, like the food coloring, it is more dense. If something floats on a liquid, like the food coloring in the salt water glass, it is less dense.
What I find interesting though, is that if you wait thirty minutes or so, the food coloring in both glasses will disperse. This is because the density of all of the liquids are close enough that the water molecules will eventually collide and join. Liquid molecules move and slip past each other. Pretty cool, huh?
More Free Resources!
John 4:14 – But whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting life.
