What Is the Process Called When a Candle Melts and Becaomes a Solid Again

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Lesson 2.5

Changing Land: Melting

Central Concepts

• Melting is a process that causes a substance to alter from a solid to a liquid.
• Melting occurs when the molecules of a solid speed up enough that the motion overcomes the attractions so that the molecules tin move past each other equally a liquid.

Summary

Students will see a small piece of ice melt on an aluminum surface. Students volition explain the free energy transfer and molecular movement which crusade the modify in land from a solid to a liquid. Students will see and talk over an animation of water ice melting and compare the state changes of water to the state changes of other substances. They volition likewise investigate sublimation of dry ice through a teacher demonstration, or video if dry ice is not readily available.

Objective

Students will be able to explain on the molecular level the process of heat transfer and molecular motility that causes a solid to cook to form a liquid. Students will too exist able to explicate how the system of water molecules is dissimilar from almost other substances when it changes state from a solid to a liquid.

Evaluation

Download the educatee activity sheet, and distribute one per student when specified in the activity. The activity sheet will serve equally the "Evaluate" component of each 5-E lesson program.

Safe

Make sure you lot and your students wear properly plumbing fixtures goggles.

Materials for Each Group

• 2 pocket-sized pieces of water ice
• 2 small clear plastic cups
• Water

Materials for the Demonstration

• Ice
• Dry Ice
• Brownish newspaper towel
• Common cold water
• Hot h2o

1. Have students lookout man a small piece of ice melting.

   Show students the video Ice Melting on Different Surfaces.

   In this video, ice is placed on two similar-looking black surfaces—ane aluminum and the other plastic. The ice melts faster on the aluminum because it is a better thermal usher than the plastic.

2. Talk over student observations.

   Inquire students:

   Where do you call back the free energy came from to melt the ice?

   The energy comes from the air and from the surface that the ice is placed on, both of which are at room temperature. Since room temperature is warmer than the temperature of the ice, energy is transferred from the surface and the air to the water ice.

   What do you think happened to the speed of the molecules in the ice when it was heated?

   The water molecules moved faster.

   Requite each student an activity sheet.

   Students will record their observations and answer questions about the activity on the activeness sheet. The Explicate It with Atoms & Molecules and Have It Further sections of the activity canvas will either be completed equally a class, in groups, or individually depending on your instructions. Await at the teacher version of the activity sheet to find the questions and answers.

   Give students time to respond the start two questions on the action sail.

3. Accept students explore how to make ice melt faster.

   Introduce the question to investigate:

   • How can y'all make the ice melt faster?

   Aid students programme and deport their experiment by asking:

   How could yous gear up an experiment to exam your method?

   Students might advise animate on the ice, holding it in their manus, or placing the ice in room-temperature or warm water. Any of these methods are fine, simply attempt to have students think about including a command equally role of the experiment. In each example, they would need 2 similar size pieces of ice—one that they warm in some way and one that they don't.

   Here is one method students could endeavour:

   Question to investigate

   Volition placing ice in water make ice cook faster?

   Materials

   • 2 small-scale pieces of ice
   • 2 small clear plastic cups
   • Water

   Procedure

   1. Add room-temperature h2o to a cup until it is about ½-full.

   2. Place a small-scale piece of ice in the water and another small piece of water ice in a cup without h2o.

      

   Expected results

   The water ice placed in the water volition melt faster than the ice in air. Since the h2o and the air are both at room temperature, it may not be obvious why the ice melts faster in the water. At that place are so many more molecules in the water that can contact the ice that the transfer of rut to the ice is much more efficient and faster in the water than in the air.

   Requite students time to write their procedure and answer the question on the activeness canvass.

4. Show an animation of ice melting.

   Show the blitheness Melting Ice.

   Bespeak out that the water molecules in ice vibrate simply don't move by each other. As the temperature increases they begin to vibrate more. Eventually their movement overcomes their attractions and they can no longer stay in their orderly crystal structure. As the ice melts, the orderly system collapses and the water molecules move by each other and actually get closer together as liquid h2o.

   Project the image Water ice and H2o

   Ask students

   How did the movement and arrangement of the water molecules change equally the ice melted?

   As energy is transferred to the h2o molecules in the ice, the motion of the molecules increases. The motion of the molecules increases enough that it overcomes the attractions the water molecules accept for each other causing the water ice to melt.

5. Compare the motion and arrangement of the molecules of a substance (not water) for each land of matter.

   Projection the image States of Matter.

   Explicate that the diagram illustrates the motion and system of atoms or molecules in a unmarried substance (non h2o) when it changes between a solid, liquid, and gas.

6. Take students compare the land changes of most substances to the state changes of water.

   Project the image States of Water.

   Tell students that the move of water molecules in each land of matter is similar to what happens for virtually substances. Calculation energy increases the motion of the molecules and causes them to motion further apart. Removing energy decreases the motility of the molecules and causes them to movement closer together. Simply, water does something very unusual when it freezes to become water ice. The molecules, which were moving closer and closer together, move further autonomously as they organize themselves into the open ring pattern shown below for ice. This is why water ice expands when it freezes.

   Ask students:

   Read more about energy and land changes in the teacher background section.

   How are the state changes of water similar to and different from the state changes in most other substances?

   For water or any other substance, molecular motion increases when energy is added and decreases when energy is removed. The chief difference between water and other substances is the arrangement betwixt the molecules of the solid and the liquid. In water, the molecules in ice are further apart than they are in liquid water. This is unusual because the molecules of solids in near other substances are closer together than they are every bit a liquid.

7. Accept groups apply their water molecules to model freezing, melting, evaporation, and condensation.

   Procedure

   Project the image Ice.

   Accept each grouping arrange their water molecules into a six-sided band of ice. Ask students to handle their models gently because they volition demand them for other lessons.

   Water ice Melts

   Have students use their models to stand for what happens when ice melts. Point out that the water molecules are closer together than they were as ice. Students could show the water molecules moving past each other.

   Water Evaporates

   Have students utilize their molecules to model what would happen if the h2o was heated and the molecules evaporated. Students should show the water molecules moving faster and breaking away from the other molecules and inbound the air.

   Water Vapor Condenses

   Have students employ their molecules to model what would happen if h2o vapor was cooled enough to cause it to condense. Students should bear witness the water molecules in the air slowing downwardly and joining together but still moving by one some other equally liquid water.

   Collect the water molecules. These models will be used again in Affiliate 5, Lesson ane.

8. Do a demonstration to compare the melting of regular water ice and dry ice.

   Allow students know that dry out ice is frozen carbon dioxide gas. Carbon dioxide gas must be very cold in society to go a solid (about −78 °C or −109 °F).

   Preparation

   You lot will need some dry out water ice for this demonstration. If yous cannot get any dry ice, show the video Dry Ice.

   Question to investigate

   Does dry ice cook the way regular water ice does?

   Materials

   • Water ice
   • Dry ice
   • Brown paper towel
   • Common cold h2o
   • Hot water (about fifty °C)

   Procedure

   1. Identify a slice of dry ice and a slice of regular ice on a brown paper towel.

   Expected results

   In a short amount of time, the ice volition begin to melt and the newspaper towel around the ice will become wet and darker. The paper towel around the dry out ice will stay dry and will non get darker. If you notice a small nighttime spot on the newspaper towel nigh the dry ice, information technology is possible that water vapor from the air condensed on the dry ice and melted onto the newspaper towel.

   If students encounter misty white fog coming from the dry ice, let them know that it is not the carbon dioxide gas itself. Carbon dioxide is colorless, odorless, and invisible. The misty smoke or fog is actually water vapor in the air that gets cold enough to condense. The h2o vapor is cooled by the dry ice and the cold carbon dioxide gas. The fog tends to migrate downward because it is carried by the carbon dioxide gas, which is more than dense than the air around information technology.

9. Discuss student observations and innovate the idea that some substances tin change directly from a solid to a gas.

   Enquire students:

   Exercise regular water ice and dry water ice melt in the same manner?

   No. The regular ice changes to a liquid, which you meet on the brown paper towel. The dry ice does not seem to change to a liquid.

   Explain to students that the reason that the dry ice does not make the newspaper towel wet is considering information technology does not melt. When energy is transferred to dry ice, the solid carbon dioxide does not cook to liquid carbon dioxide. Instead, the solid changes directly to a gas. This process is called sublimation. Sublimation occurs when molecules of a solid movement fast plenty to overcome the attractions from other molecules and become a gas. Since frozen carbon dioxide never becomes a liquid under normal pressure, it is called dry ice.

10. Show students what happens when dry out ice is placed in water.

    Place a piece of dry water ice in water and then add together a footling dish detergent or testify the video Dry Ice in Water.

    Expected results

    Bubbling volition form and a misty white fog volition be produced. Since the water is much warmer than the dry ice, energy is transferred from the water to the dry ice, causing it to change from a solid to a gas and bubble through the water. After detergent is added, a mound of bubbles will form.

    Students volition be curious well-nigh all of the fog coming out of the cup. Tell them that some water changes to water vapor within the bubbles of carbon dioxide gas and then condenses. This causes fog within the bubbles which escapes when the bubble pops.

    Ask students:

    You saw that the dry ice sublimates very apace in water. What could y'all do to brand dry out water ice sublimate even faster?

    There are several ways to brand dry out ice sublimate faster. Ane choice is to put the dry ice in hot water.

    Place a slice of dry ice in ¼ cup of cold water and another piece in ¼ cup of hot water. Or evidence the video Dry out Ice in Hot and Common cold Water.

    Expected results:

    Much more fog will be produced from the cup with hot water.

    Tell students that more than fog is produced when dry out ice is placed in hot water considering the transfer of energy and sublimation happens faster. This causes the fog to exist produced at a faster charge per unit.

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Source: https://www.middleschoolchemistry.com/lessonplans/chapter2/lesson5

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