Cold and Warm Fronts

Fourth grade is learning a lot about the weather. We have studied clouds, weather instruments, the water cycle, and the atmosphere. Students know that cold water is dense…it is more heavy, and the water molecules stick closer together while moving slowly. Warm water is less dense…warm water is lighter, and the water molecules move faster and separate at a greater distance.

Today during lab, students were asked the question, “What will happen when two air masses meet?” Students made predictions based on previous knowledge and a starter demonstration. The lab began with a quick demonstration of observing a clear cup of cold water. A few drops of blue food coloring was added to the cold water cup. Students observed the blue food coloring dispersing into the cold water cup. Some things that were observed was that the blue food coloring did not mix well and did not disperse evenly. Also students observed that the blue food coloring sank and collected in the bottom of the cold water cup.

Next, students observed a hot water clear cup of water. Students observed A few drops of red food coloring was added to the hot water cup. Students observed the red food coloring dispersing into the hot water cup. Some things that were observed was that the red food coloring did in fact mix well and it did disperse evenly throughout the cup of warm water. Also students observed that the red food coloring did not sink and collected more at the top of the hot water cup. This started demonstration was interesting, as it supported facts we already know about warm and cold water molecules.

Next, fourth graders were able to conduct their own experiments to further understand warm and cold fronts. Students used clear tubs of room temperature water. The transparent room temperature water in the clear, plastic tub containers represented the atmosphere/ troposphere. Students understand that the atmosphere is made up of water vapor/water molecules. Next, students were asked the question, “what will happen when warm and cold fronts meet?” Students were then give blue ice cubes and also a cold blue water cup to represent the cold air mass. Students were also given a warm, red water cup to represent a warm air mass. We then added both cups (warm and cold…red and blue water cups) on opposite ends of the “atmosphere” tubs of water. It was exciting to observe the results of our experiment of what will happen when warm and cold fronts meet. Students observed that the warm water (red) moved to the top and took up less space. The cold water (blue) moved to the bottom and took up more space. We observed that most of the “atmosphere” was blue rather than the small portion of red at the top. This observation supports our former knowledge that cold air sinks down below warm air because cold air..cooler water vapor… is more dense…it is heavier. Our predictions supported the conclusion: The blue cold water sank to the bottom because it is more dense. The red warm water rose to the top because it is less dense.

While thinking about the weather, we wondered, “Do cold and warm fronts mix?” Our experiment with the blue and red water supports our thinking… the warm and cold fronts do not mix…they do not collaborate…they separate! We also have learned that when a cold front meets a warm front, rain is likely.

Learning more about the weather while conducting hands on experiments is fun!