| This is designed for third grade, but is easily adaptable to both higher and lower grades. However, I would not suggest it for first grade due to the pushing/shoving involved. TEKS are listed for Texas teachers. This lesson has a strong tendency to "stick in the mind" due to the hands-on method of teaching, leaving an indelible mental image for students to recall. Microwaved Ice Cube Lesson Plan TEKS: 3.1: (A) demonstrate safe practices during field investigations; 3.2: (C) analyze and interpret information to construct reasonable explanations from direct and indirect evidence; (D) communicate valid conclusions; 3.3: (C) represent the natural world using models; 3.7: (B) identify matter as liquids and solids. Objective: Students will understand how microwaves affect water molecules in both liquid and solid states. Focus: Comparison of an ice cube in a microwave for 15 seconds vs. a filled pastry for 15 seconds. (The instructor must verify the time limit and temperature setting and may have to make adjustments. 15 seconds was good for my microwave at a power setting of 10.) Materials: Microwave oven, ice cubes, filled pastries, paper towels for clean up. Explanation: 1. Food and air contain water molecules. 2. The microwave heats up the water molecules. 3. The water molecules are pushed into each other, bounce back. This occurs over and over again. 4. The bouncing effect causes friction. 5. The friction heats up the surrounding food. Laboratory Experience/Field Activity: Liquid form: 1. Have the students make a circle. 2. Enough students move from the outside circle to inside the circle to form a compact center. 3. Explain that the students inside the center are water molecules. The students on the outside circle are the microwaves. The water molecules just wander around inside the circle of microwaves. 4. When you blow the whistle, the microwaves push the water molecules in a straight direction. To do this, as a water molecule comes toward the microwave, the microwave can take several steps towards the water molecule to make the push. 5. The water molecules, pushed by the microwaves, move forward until they bump another water molecule. They then bounce backward until coming up against another water molecule or microwave. 6. This continues until the water molecules get warm. Solid form: 1. Have the students make a circle. 2. Take four students and put them in the very center of all the other students. Have them wrap their arms around each other to show they are one. 3. Explain that the students at the center are frozen water molecules or one ice cube. These students cannot move. They are frozen. If they move, the student who moves must detach from the "cube" and be a water molecule. (That piece of the cube "melts".) The students surrounding them within the circle of microwaves are water molecules also except they are not frozen. The other water molecules just wander around inside the circle of microwaves. 4. When you blow the whistle, the microwaves push the water molecules in a straight direction. To do this, as a water molecule comes toward the microwave, the microwave can take several steps towards the water molecule to make the push. 5. The water molecules, pushed by the microwaves, move forward until they bump another water molecule. If they bump gently, they stick together and get larger with each gentle bump of another water molecule. If they bounce off another student, they are moving at a higher rate of speed. (This is good, it will help dislodge the attachment of the frozen ice cube and the four students will begin to separate, thereby "melting".) They then bounce backward until coming up against another water molecule or microwave. 6. Eventually, the students in the center will break up (due to the pressure of the other students bouncing on and off of them) and join the non-frozen water molecules. Closure: Ask questions relating to the exercise: � How long did it take to "melt" the ice cube? � What caused the ice cube to melt? (friction caused by the bouncing) � Why didn't the ice cube melt faster? (The ice cube will last approximately 15 seconds without melting. The microwave used to test this on was set at the highest power - 10. The filled pastry will be very hot. The ice cube only melts because the temperature is no longer zero degrees centigrade but at room temperature. Even at one minute in the microwave, a one square inch ice cube didn't completely melt. The water molecules are locked in position and can't bounce to and fro causing friction, heat and melting action.) |
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