Melting ice

Year level: Upper primary Learning outcome Students will investigate how melting ice contributes to sea level changes. Materials required: large, rectangular container to hold water rectangular piece of wood, about 20 cm x I0 cm and 3 to 4 cm thick. The wood should be of low density for it to float readily on water. supply of ice cubes and water Experiment A Procedure: Partly fill the container with water. Cover three quarters of the water surface with ice cubes, and ensure that the free water surface is at least 2 cm below the container rim. Carefully measure the height of the free water surface below the rim of the container. Measure and record the temperature of the free water, and also its distance below the rim of the container at intervals of five minutes until all the ice melts. Plot the temperature of the free water against time. Explain the shape of the plot. Why is this so? (Hint: Where was the ice?) Experiment B Procedure: Mark the points of the compass (N, E, S, W) on the surface of the piece of wood. Draw E-W lines at 1 cm intervals from N to S. Mark lines at 2 mm intervals along the N and S edge. Partly fill the container with water and float the wood in the water. Place one or two ice cubes on the N edge of the floating wood. Note the level of the water in the container and on the N and S edges of the wood as the ice melts. Explain what happens to the water level in the container as the ice melts. Explain what happens to the N and S edges of the block of wood as the ice melts. Imagine that the wood block represents a continent ‘floating’ on the mantle of the earth. The ice cubes represent an ice sheet or glacier field overlying Earth’s surface. Discuss: How does this experiment help to understand the impact of melting glaciers and other land-based ice masses have on changes in sea level? Under what circumstances will the melt water submerge the continents on which the ice used to be? How important is an associated program which can independently measure vertical land movements? Assessment task Describe why it is important that accurate measurements of sea and levels are collected.