Convection in Water Investigation 5, Part 2 TG- P.163-164

How heat is transferred…. Radiant energy strikes Earth’s surface Conduction Radiation Surface molecules increase their motion Molecules of air touches the heated surface of Earth TG- p.165 The surface absorbs the energy Energy is transferred from surface to the air

Heat in solids Molecules are locked together Molecules begin to vibrate, continues through the rest of the molecules creating heat Absorbs radiant energy TG- p.165

Heat in fluids (liquids and gases) Molecules are not locked into position Move around freely Heat is transferred by one molecule touching another TG- p.165

Challenge of the Day Make layers of plain water that are different temperatures. Predict and record the colors of the layers on page 27 of your lab book. TG- p.165 Student Lab Notebook P.27

Materials 3 vials (two with caps) 2 plastic-foam cups (to insulate cold and hot water) 2 pipettes 1 plastic cup TG- p.165 Student Lab Notebook P.27

Procedure red, blue, and clear Fill a vial Create three layers in the vial red, blue, and clear 3/4 full Room Temperature Water TG- p.165-166 Student Lab Notebook P.27

Do not bump or jostle an experiment in progress Warning!!!!! Do not bump or jostle an experiment in progress TG- p.165-166 Student Lab Notebook P.27

How to successfully layer Wait for water to stop moving Room Temperature Water TG- p.167 Student Lab Notebook P.27

How to successfully layer Wait for water to stop moving Carefully introduce the blue water under the room temperature water Room Temperature Water TG- p.167 Student Lab Notebook P.27

How to successfully layer Wait for water to stop moving Carefully introduce the blue water under the room temperature water Room Temperature Water TG- p.167 Student Lab Notebook P.27 Carefully introduce the red water on top of the room temperature water

Layered vial Stand for 5 minutes Discuss with your partner what is happening TG- p.167 Student Lab Notebook P.27

Observations What happened in your vial after is sat undisturbed for a few minutes? The red water starts to sink to the bottom of the vial What do you think caused the red water to start to descend? The warm red water cooled Increasing the density of the red water TG- p.167 Student Lab Notebook P.27

Why? Hot red water layered on top of the room temp water? Cold blue water layered under the room temp water? Less Dense TG- p.167 Student Lab Notebook P.27 Denser

Heating the Layered Vial Create the 3 layered vial Put 1 cm of hot water in a plastic cup Place the layered vial carefully in the cup of hot water and observe. TG- p.167 Student Lab Notebook P.27

Heating the Layered Vial What did you observe? How can you explain your observations? Can you explain the energy transfer that happened? TG- p.167 Student Lab Notebook P.27

Molecular model Water becomes less dense as its temperature increases! As heat is absorbed by water, the molecules move faster and bang into each other with greater force and frequency. This drives the molecules farther apart. When molecules are forced farther apart, the water becomes less dense. TG- p.168 Student Lab Notebook P.27

Convection When a mass of fluid is warmer or colder than the surrounding fluid, the mass will rise or sink in the surrounding fluid. This motion of masses is called convection! This is the third way heat transfers. TG- p.168 Student Lab Notebook P.27

Convection The motion of masses or streams of fluid, due to difference in density resulting from temperature. TG- p.168 Student Lab Notebook P.27

Reading “Convection” on pages 32-33 TG- p.168 Student Resource Book P.32-22