Write the word erosion on the board. Give students five minutes to write in their science journals a definition of what they think erosion is and make predictions on how the block will look on day 2, day 3, and through the rest of the week. On day 2, catch some of the water run-off for students to analyze. Take 25ml of the run-off and 25ml of the drip water, place in glass containers and allow both to evaporate. Have students predict what will happen in the two different containers and record predictions in science journals.
Students observe the model daily.
Give them five minutes of journal time to write down what they see taking place on the salt block and in the containers with the two different waters. Require students to compare their observations to the predictions that they made on day 1 and day 2 as part of the writing process. After the week is through and students begin to formally study erosion, discuss with students what they think erosion is. Share journal entries and compare predictions with what really happened. Tell students that they have been observing erosion on a salt block over the past week.