Layered: How Does Hail Form?
How Does Hail Form?
- Wax paper
- Cold tap water
- Sheet of black construction paper
- Desk lamp
- Paper towel
- Magnifying lens
NOTE: You must have access to a freezer.
- Cut a piece of wax paper to fit into the bottom of the saucer. Place the paper in the saucer.
- Fill the eyedropper with water.
- Squeeze about five drops of water onto the wax paper spacing them apart from each other.
- Place the saucer in the freezer.
- After 30 minutes, remove the saucer. Fill the eyedropper with water and place one drop of water on top of each frozen drop.
- Immediately replace the saucer in the freezer.
- Repeat steps 5 and 6 two more times.
- Wait one hour after the last addition of water, then remove one of the pellets from the saucer.
- Place the black paper under the desk lamp and put the pellet on the paper.
- Use the paper towel to dry the pellet, then turn it so that its flat side is facing up.
- Use the magnifying lens to observe the structure of the ice. View it from different angles. Use the other pellets when the first one melts.
The frozen pellet looks like a piece of ice that is rounded on one side and flat on the other. The surface of the flat side has a circular milky center with three rings of ice surrounding it. The rings in the pellets may vary; some are clear and some are milky looking.
Milky-looking ice is formed when water containing dissolved air bubbles freezes. If the air bubbles escape as the water freezes, clear ice is formed. As each drop is added, the clarity or cloudiness of the ice produced depends on the amount of dissolved air bubbles that remain in the water as it freezes. Hail, like the pellets in this experiment, is formed by the addition of ice layers to a central piece of ice. Unlike the ice pellets in the experiment, hail is formed in thunderstorm updrafts. Sometimes water droplets in clouds are prevented from falling by strong updrafts of wind. These droplets are swept up into a cold cloud layer where they freeze and eventually fall when the wind can no longer support their weight. As these pellets of ice "fall through warmer moist air, they become covered with raindrops. Another updraft sweeps the forming hailstones back into the upper, colder part of the cloud where sub cooled water freezes on it. Snow may also stick to these pellets, adding more layers and weight to the hailstones. As the hailstones move up and down in the cloud, they are covered by more and more layers of ice. When they finally become too heavy to be held up by the up currents of air, they fall to the ground.
Does the temperature of the water drops affect the cloudiness of the ice layers that form the hailstones? Repeat the experiment twice. First, use water that you have chilled to 50 degrees Fahrenheit (10 degrees Celsius) by placing ice cubes in a cup of cold tap water. Repeat the experiment, using subcooled water. Prepare the subcooled water by filling a small metal food can with ice and then covering the ice with water. Set the can in a larger container, such as a coffee can or bowl that is as tall as the can. Fill the large container half full with ice and then sprinkle a layer of rock salt over the ice. NOTE: Do not get salt inside the can. Add a second layer of ice and rock salt to fill the container. Continue to add ice and salt to the larger container as needed throughout the experiment to keep the water subcooled. Use a thermometer to measure the temperature of the two containers of water.