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When we look out at the ocean, or any big body of water, you might think that the only moving water is the waves on top. Believe it or not, there is actually moving water under the surface. We call this moving water below the surface, a current. There are many reasons why there are currents, but today we’re going to experiment with temperature and density.
Materials:
- 2 Containers, one tall and clear
- Cold Water
- Warm Water
- 2 Colors of Food Coloring
- Ice
- Salt
Procedure:
1. Add some cold water to the clear container.
2. Mix in salt until mostly dissolved.
3. Mix in one color of food coloring.
4. Add ice to your clear container. This water needs to be very cold.
5. Fill the other container with warm
water.
6. Mix the other food coloring with the warm water.
7. Pour your warm water gently down the inside of the cold-water container.
8. Watch what happens through the sides of the container!
What happened when you poured in the warm water? Did it float? Or did it sink? Even though it might have been pulled down by gravity when pouring into the cold water container, the warm water with no salt should float to the surface because it’s not as dense as cold water.
Density is how much stuff is packed into a certain space. The denser something is, the heavier it will be, while the less dense is less heavy. In the ocean, cold water is denser because all the little tiny pieces of water, called molecules, move slower than hot water. Salt water is also denser than
fresh water is. Did this have an effect on your experiment? What do you think would happen if you did the opposite? Try this activity again but in reverse. Start with warm water and pour in cold water.
Ocean currents occur when cold water sinks to the bottom, and warm water floats to the surface. As warm water approaches the North or South Pole, the water starts to get cold, and will sink to the bottom of the ocean. As cold water heads towards the equator and heats up, it will start to float to the surface. This pushes and pulls the water all across the Earth.
Northern Virginia Science Center Foundation is a 501(c)(3) non-profit organization that operates the Children's Science Center Lab at Fair Oaks Mall and STEM programs traveling to schools and other community venues across the region. The Foundation is also developing the Northern Virginia Science Center in Dulles, VA, a world-class, interactive regional science center for families, students and learners of all ages made possible through a pivotal public-private partnership. Learn more about our mission today at childsci.org and our vision for the future at novasci.org.
