Tidewater glaciers are very large rivers of ice that flow into the sea. These glaciers sizzle and hiss as the slow-moving ice thaws in the听seawater, sounding like food sizzling in a frying pan. These noises are caused by the release of trapped air in the ice. These tiny bubbles aren鈥檛 just making noise, they are also giving us clues to crack our past! Find out what causes the crackling sound in this experiment.
Safety First!
Chemists use many strategies so their experiments are as safe as possible. Read the听Science Safety Tips听to find important practices for kids and chemists to do before, during, and after every chemistry activity.
Materials Required
- 2 cups or dishes of room-temperature water
- 1 packet of Nerds candy
- 1 packet of Pop Rocks (or other 鈥減opping鈥� candy)
Procedure
Part 1: Nerds
- Place one of the cups of water on a table in a quiet space.
- Pour some of the Nerds candies into the water. Wait for two minutes. What do you observe?
- Read the list of ingredients on the Nerds box and ask for ideas of why the Nerds candies acted the way they did.
Part 2: Pop Rocks
- Pour some of the Pop Rocks into the second cup of water. Wait for two minutes and make observations.
- After the observations, read the list of Pop Rocks ingredients and ask for ideas to explain what happened.
What did you observe?
When the Nerds candies are placed in the water, you can see the candy dissolve. This is because Nerds candies are mainly sugar, which easily dissolves in water. Depending on the color, as the candy dissolves, it might change the color of the water. Notice when Nerds dissolve, there is no sound.听
When the Pop Rocks are placed in the water, they also begin to dissolve. However, as the sugar dissolves, a popping sound can be heard.听
Where鈥檚 the chemistry?
Candies like Pop Rocks are made by heating the sugars sucrose, lactose, and corn syrup to boiling. Carbon dioxide (CO2) bubbles up through the molten sugar mixture at a pressure of around 600 pounds per square inch, which is about seventeen times the air pressure in a small car tire! The mixture is then cooled rapidly under pressure to prevent the gas from escaping as the candy becomes solid.听
When you eat the candy, the sugary shell around the gas bubbles dissolves and the pressure is released with a popping sound. Each piece contains tiny bubbles of carbon dioxide that remain trapped until the candy hits the water (or the saliva in your mouth). The water/saliva allows the sugar to dissolve, and then the gas escapes with a satisfying pop!听
When snow falls, anything in the air at that time falls with the snow. This is why layers of snow and ice contain more than just water. They can contain particles from forest fires and volcanoes, pollen, and dust picked up by the wind. They can also contain bubbles of gases from the atmosphere, and many other small amounts of chemicals. These materials in ice are not visible to the human eye. Scientists need special tools to observe and analyze them.听听
When ice melts (changing from solid to liquid), gases are released鈥攋ust like just like when Pop Rocks dissolves in water. The gases can tell us what was in the earth鈥檚 atmosphere when the ice was formed and the gas was captured. Scientists get ice core samples of glaciers to study these gases before the ice melts. See the听Let鈥檚 Explore the Cores article听in this issue to learn more about ice cores and how they give us information about our past.
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