The purpose of this activity is to introduce students to the concepts of equilibrium and conservation of mass through a model of a closed cyclic system, a pan water cycle.

TEACHER RESOURCES Teacher Materials Student Activity Student Answer Sheets Learning    Goals/Standards COMPUTER MODELS STELLA Versions isee Player software Right-click to download the models PC Format Mac Format Vensim Version Vensim PLE Software Right-click to download the model Pan Water Cycle Excel Version Right-click to download the model Pan Water Cycle NetLogo Version Right-click to download the model Pan Water Cycle

THE MODEL DIAGRAM THE EQUATIONS Water_in_Air(t) = Water_in_Air(t - dt) + (Evaporation - Condensation) * dt    INIT Water_in_Air = 0 {ml} Water_in_Pan(t) = Water_in_Pan(t - dt) + (Precipitation - Evaporation) * dt    INIT Water_in_Pan = 100 {ml} Water_on_Cover(t) = Water_on_Cover(t - dt) + (Condensation - Precipitation) * dt    INIT Water_on_Cover = 0 {ml} Evaporation = Water_Temperature * Amount_of_Evap_per_degree_C Condensation = 0.5 * Water_in_Air Precipitation = 0.5 * Water_on_Cover Amount_of_Evap_per_degree_C = 1/20 {ml/min/degree Celsius} total_water = Water_in_Air + Water_in_Pan + Water_on_Cover Water_Temperature = 100 {degrees Celsius}

THE OUTPUT

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