4 States Of Matter

Becky McCoy

Title: STATES of MATTER Timing: 50 minutes Target Audience: High school Physics

Objectives: The Students Will Be Able To: • Identify what causes matter to change state. • Relate expansion of matter to addition of thermal energy. • Compare/contrast evaporation and boiling. • Use equations to calculate phase changes mathematically. The Teacher Will Be Able To: • Provide opportunities for students to observe what happens to molecules as water experience hot and cold changes in temperature. • Evaluate students’ progress in understanding the concept of heat. • Give students evidence of phase change properties.

Standards Assessed: Advanced Placement (AP) Physics B Competency Goal #31 • Objective 3.02: Evaluate and investigate temperature and heat

Misconception(s) Addressed: • •

Temperature rises while a substance is melting, and falls while a substance is freezing. Misunderstanding of the temperature of a phase change.

Concept Map Vocabulary: • • • • • • • • • •

Phase Change – the physical change from one state of matter to another. Melting point – the temperature at which a substance changes from a solid to a liquid. Freezing point – the temperature at which a substance changes from a liquid to a solid (equal to melting point for the same substance). Boiling point – the temperature at which a liquid boils. Vaporization – the process by which matter changes from a liquid to a gas. Boiling – vaporization that occurs as a result of a liquid reaching its boiling point. Evaporation – vaporization that occurs at the surface of a liquid, below its boiling point. Condensation – the change of a substance from gaseous to liquid form. Heat of Fusion – the amount of energy required to freeze or melt 1kg of a substance at its freezing/melting point. Heat of Vaporization – the amount of energy required to condense or vaporize 1kg of a

Becky McCoy

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substance at its condensation/boiling point. Conservation of Energy – in a system, energy is never lost or created; however, it may change forms.

Lesson Plan Aim: Observe and analyze phase changes. Physics Push-Up: Molecular Movement (10 min) Have a group of four or five students demonstrate each state of matter and the movement of molecules in that state by going to the front of the room and acting it out. Give them 5 min to plan before performing.

Demonstration: Milk Container Phase Change3 (10 min) The teacher should perform this demonstration. During the 20-minute period of observation, the teacher should be giving Teacher Talk while students casually observe what is happening to the milk container. Materials: • 2 Milk Containers (one with a screw on cap and one with a snap on top) • Water • Hot Plate • Beaker Procedure: • Heat 400mL of water to boiling in a beaker. • Pour the water equally into the two milk containers and close the tops tightly. Questions to Ask: During Boiling: • What is happening to the water? (Energy is being transferred to the water molecules from the heat source.) • What is heat? (The transfer of energy between two objects/substances at two different temperatures.) • Why does it matter that the water is heated? • As the water heats, what is happening to the water particles? (They are beginning to move faster.) • What is happening between the particles? (They are spreading farther apart from one another.) During Vaporization: • What is happening to the milk container? • Why is this happening?

Becky McCoy • What is making the container do this? • How could we test this idea? During Condensation: • Now what is happening to the milk container? • Why is this happening? • What is the difference between the water at this time versus the water when we initially poured it into the container? • What change is happening to the water to make this event occur?

Teacher Talk: Phase Change Equations (10 min) Begin with a short version of Four Corners by asking the following questions. One side of the classroom should be yes and the other no. Or have students remain seated and raise hands for yes and no. Questions to Ask: • Can water and ice coexist? • Can water and ice coexist without the ice melting or water freezing? • Can water and steam coexist? • Can water and steam coexist without the water vaporizing and the steam condensing?

Temperature (oC)

Ask students what the temperature ranges are for ice, water, and steam (water vapor). Write them on the board. Next, draw a phase change graph for water using the information provided by the students.

Solid

Solid & Liquid

Liquid

Liquid & Gas

Gas

100oC

0oC Thermal Energy Transfer at a constant rate  In order to review the reason for the shape of the curve, show the students the online demonstration: http://netcamp.prn.bc.ca/nuggets/heatingcurve.swf. Remind students to continue to observe what is happening to the milk container. Allude to the Extra Credit from the homework the night before. Explain to students that the Law of Conservation of Energy can be used to explain mathematically what is occurring during

Becky McCoy a phase change. Go through the calculations to show what happens to 1.0kg of ice at -5.0oC when it is placed in 1.0kg of water at 70oC. Explain the process of Heat of Fusion so students understand the purpose of the 80Cal. E = mcT (1.0kg)(1.0)(- 5.0 o C) + (2.0kg)(1.0)(70 o C) = - 5.0 + 140 = 135Cal 135Cal - (80Cal)(1.0kg) = 155Cal (3.0kg)(1.0)(T) =155Cal T = 51.7 o C This time show students what happens when there is more than 1.0kg of ice with regards to the Heat of Fusion. Calculate 2.0kg of ice at -5.0oC and 3.0kg of water at 70oC. E = mcT (2.0kg)(1.0)(- 5.0 o C) + (3.0kg)(1.0)(70 o C) = - 10 + 210 = 200Cal 200Cal - (80Cal)(2.0kg) = 40Cal (5.0kg)(1.0)(T) = 40Cal T = 8.0 o C

Activity Review: Sharing Observations (5min) Ask students what they observed at each stage of the milk bottle experiment. Allow other students to write down observations they did not make. Be sure students know the milk container expanded when hot and condensed when cooled. Students should know the snap on cap popped off when hot.

Homework: Hot Homework: Dancing Molecules2 & Balloon Activity (2 min) Give every student a balloon. They should take it home and blow up and tie off the balloon. The string should be tied carefully so that it is tight around the outside of the balloon. Put the balloon and string inside of the freezer for 30 minutes. During this 30 minutes, they should make predictions about what should happen to the balloon after 30 minutes and after an hour. After that time, they should check the balloon and record their observations. Check the balloon after an hour and record any further observations.

Exit Strategy: Index Cards (3 min) Have students re-answer the questions asked at the beginning of Teacher Talk on an index card. • Can water and ice coexist? • Can water and ice coexist without the ice melting or water freezing? • Can water and steam coexist? • Can water and steam coexist without the water vaporizing and the steam condensing? • What changed or didn’t change your thinking? • What is still confusing?

Becky McCoy

Assessment: •

Formative: o Student answers during Four Corners activity, and again during Index Card exit strategy. o Student reactions during Activity Review. o Homework review the next day.

References: 1

- http://www.ncpublicschools.org/curriculum/science/scos/2004/33apphysicsb – Serway, R. et al. College Physics. Thompson Publishers: New York. 6th Edition. p354. 3 - Group activity found online, written by: Sally Ferrelle, Oglethorpe Academy, Savannah, GA 2

Becky McCoy Name_________________________________ Date ___________

HOT HOMEWORK: DANCING MOLECULES Calculate the following problems. Show all work and circle answers.

A 100g cube of ice at 0oC is dropped into 1.0kg of water that was originally at 80oC. What is the final temperature of the water after the ice melts? (Heat of Fusion=80)

A 100g ice cube at 0oC is placed in 650g of water at 25oC. What is the final temperature?

A 50g ice cube at 0oC is heated until 45g has become water at 100oC and 5.0g has become steam at 100oC. How much energy was added to accomplish this? (Heat of Vaporization=540)

Steam at 100oC is added to ice at 0oC. Find the amount of ice melted and the final temperature when the mass of steam is 10g and the mass of the ice is 50g. Repeat with steam of mass 1.0g and ice of mass 50g.