In this activity, students will predict, observe, and compare melt rates of ice under different temperature conditions and in different solutions.
- This activity requires flowing water. If available, a faucet with cold and warm water can be used. Otherwise, use pitchers with warm and cold water. However, note that the rate at which water is poured from a pitcher can vary greatly. Pouring through a funnel can help regulate the flow of water.
- Consider having towels on hand for cleaning up spills and splashes.
- Safety: Hot water can scald. Make sure students are using water that is below 110° F (43° C).
- Use the leftover water from this activity to water a plant or save it for another activity instead of dumping it down the drain.
The Greenland ice sheet is the second largest body of ice in the world right behind the Antarctic ice sheet. As the ice sheet melts, the water flows into the ocean, contributing to global sea level rise.
As glacier ice melts, some of the water can reach the ground below the ice, forming a river that channels glacier water into the ocean. As it flows into the ocean, this cold, fresh meltwater will rise above the warmer, salty ocean water because freshwater is less dense than salt water.
The rising cold water then draws in the warmer ocean water, melting the face of the glacier from the bottom up. This creates an overhang of ice, the edges of which will eventually break off in a process called calving, which quickly adds more ice to the ocean. As ocean waters warm, this calving process speeds up.
Understanding these different factors that contribute to Greenland's melting ice sheet is an important part of improving estimates of sea level rise. The Oceans Melting Greenland (OMG) mission was designed to help scientists do just that using a combination of water temperature probes, precise glacier elevation measurements, airborne marine gravity, and ship-based observations of the sea floor geometry. The mission, which ran from 2016 to 2022, provided a data set that scientists can now use to model ocean/ice interactions and improve estimates of global sea level rise.
Part 1: Still Water
- Introduce or ask students what they know about glaciers, ice melt, and sea level rise. Consider using the lesson What’s Causing Sea-Level Rise? and having students read 10 Interesting Things About Glaciers from NASA's Climate Kids website prior to this activity.
If necessary, remind students that glaciers are huge, long-lasting masses of ice sitting on landmasses that form over many years. Snow accumulates and compresses into glacier ice under the weight of newer layers of snowfall above. Glaciers are not to be confused with icebergs, which are large chunks of glaciers or ice sheets that have broken off and float freely in the ocean.
- Tell students they are going to compare how quickly ice melts under different conditions. Ask students to predict what will happen to the ice and water temperature under the following conditions. Predictions can be relative (e.g., “Ice will melt faster in condition A”) or specific (e.g., “Ice will melt in X seconds in condition A”).
- Ice cube placed in a dish of room temperature water
- Ice cube placed in a dish of hot water
- Ice cube placed under flowing room temperature water
- Ice cube placed under flowing hot water
- As a class demonstration, or in groups of two to four students:
- Fill one dish with room temperature water.
- Measure and record the temperature.
- Gently place an ice cube in the dish and record how long it takes for the ice cube to melt. There should be enough water in the dish so the ice cube floats.
- Measure and record the water temperature after the ice has melted.
- Repeat the procedure using hot water. These two steps can be done at the same time if students are able to monitor and record the melt time for both cubes of ice.
- Ask students to share their results and observations.
Part 2: Flowing Water
- Under a faucet of running water, or using water from a pitcher (see Management tip about using a funnel), complete the following as a demonstration or in groups of two to four students:
- Run the faucet and adjust as needed to get the water at the same room temperature as in the previous step. Record the temperature.
- Place an ice cube in a colander or mesh strainer and run it under the faucet, or pour water from the pitcher onto the ice cube. Record how long it takes to melt.
- Repeat the procedure using hot water, matching the temperature from the earlier step.
- Ask students to share their results and observations.
Part 3: Salt and Freshwater
- Mix water with food coloring and freeze into ice cubes (two per group or two as a class demo).
- Tell students they are going to add a colored ice cube to a saltwater solution and to a freshwater solution and allow the ice to fully melt. Ask them to make predictions about what will happen.
- In a clear beaker or plastic container, add 1 teaspoon of salt to 1 cup of water and stir until the salt is dissolved. Allow time for any water movement to stop.
- Pour the same amount of freshwater into a clear beaker or plastic container. Allow time for any water movement to stop.
- Gently add one ice cube to each container, taking care to not disturb the water too much.
- Have students observe each container and take notes. It may be helpful for students to place a white sheet of paper behind the containers to see more details.
- When the ice has melted, ask students to compare their observations to their predictions and develop hypotheses about the phenomena they observed.
- If necessary, explain to students that because one container has salt water, and one has freshwater, the less dense meltwater floats on salt water but has the same density and mixes with the freshwater.
- Connect this phenomenon to the movement of fresh meltwater from under a glacier into warm ocean water.
- Which ice cube melted fastest? Which melted slowest? How could these results be altered?
Changing the flow rate and temperature of the water will change how quickly the ice melts.
- What do these results tell you about the melting of glaciers in different conditions?
Currents of warm ocean water will melt glaciers faster than still water.
- What would happen to cold meltwater that flows out from under a glacier into salty ocean water?
The freshwater will rise because of its lower density, drawing in warmer ocean water against the face of the glacier.
- Students should accurately measure and record temperature and melt times.
- High school chemistry students should accurately calculate what the final temperature of the water in the containers will be in Part 1 by using specific heat capacity.
- Ask students to investigate whether ice exposed to warm or room temperature air would melt more quickly or more slowly than ice exposed to still or flowing warm or room temperature water.
- Lower elementary: Ask students to predict what would happen if some of the water was removed from the containers in Part 1 and placed in the freezer. Freeze some of the water to confirm their predictions.
- Upper elementary: Remove some of the salt water from Part 3 and place it on a flat, non-porous surface to dry. Ask students to predict what will happen when the water evaporates. Repeat the process with freshwater. Allow water to dry overnight and compare predictions to observations of what occurred.
- Middle school: Ask students to draw or describe the changes in particle motion, temperature, and state(s) of matter at the beginning and end of their observations.
- High school: Using the known masses and temperatures of the ice cubes and water in Part 1, have students calculate the final temperature of the water in the room temperature bowl and the hot water bowl using the formula m1CΔT1 = m2CΔT2. Then, have them compare their calculations to observed results.
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