what happens at an atomic level when a solid changes in to a liquid.

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Lesson 2.five

Irresolute State: Melting

Cardinal Concepts

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

Summary

Students will see a small slice of ice melt on an aluminum surface. Students will explain the energy transfer and molecular motion which cause the change in country from a solid to a liquid. Students volition see and discuss an animation of water ice melting and compare the land changes of h2o to the state changes of other substances. They will also investigate sublimation of dry water ice through a teacher demonstration, or video if dry out water ice is non readily bachelor.

Objective

Students volition be able to explain on the molecular level the procedure of heat transfer and molecular motion that causes a solid to melt to form a liquid. Students volition likewise be able to explain how the arrangement of water molecules is dissimilar from most other substances when it changes state from a solid to a liquid.

Evaluation

Download the student activity sail, and distribute i per student when specified in the activeness. The activeness sail will serve as the "Evaluate" component of each v-E lesson plan.

Safety

Make sure you and your students habiliment properly fitting goggles.

Materials for Each Group

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

Materials for the Demonstration

• Ice
• Dry Water ice
• Brownish paper towel
• Cold water
• Hot water

1. Have students picket a small piece of ice melting.

   Show students the video Ice Melting on Unlike Surfaces.

   In this video, ice is placed on two similar-looking blackness 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. Discuss student observations.

   Ask students:

   Where do you lot think the energy came from to cook the water 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 ice.

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

   The water molecules moved faster.

   Requite each pupil an activity sheet.

   Students will tape their observations and answer questions virtually the activity on the activity sheet. The Explain Information technology with Atoms & Molecules and Have It Further sections of the activity sheet will either be completed every bit a class, in groups, or individually depending on your instructions. Look at the teacher version of the activity canvass to find the questions and answers.

   Give students time to answer the first ii questions on the activity sheet.

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

   Introduce the question to investigate:

   • How can you brand the ice cook faster?

   Help students plan and bear their experiment by request:

   How could you ready up an experiment to test your method?

   Students might propose breathing on the ice, holding it in their manus, or placing the ice in room-temperature or warm h2o. Any of these methods are fine, merely try to accept students remember nigh including a control as office of the experiment. In each instance, they would demand two similar size pieces of ice—one that they warm in some manner and one that they don't.

   Here is one method students could attempt:

   Question to investigate

   Volition placing ice in h2o brand ice melt faster?

   Materials

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

   Procedure

   1. Add room-temperature water to a loving cup until it is almost ½-total.

   2. Place a minor piece of ice in the h2o and some other small piece of ice in a loving cup without water.

      

   Expected results

   The water ice placed in the h2o volition melt faster than the water ice in air. Since the water and the air are both at room temperature, it may non be obvious why the water ice melts faster in the water. There are and 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 h2o than in the air.

   Give students time to write their procedure and answer the question on the action sail.

4. Prove an animation of water ice melting.

   Show the animation Melting Ice.

   Point out that the water molecules in ice vibrate but don't movement past each other. Equally the temperature increases they begin to vibrate more. Eventually their movement overcomes their attractions and they can no longer stay in their orderly crystal construction. As the ice melts, the orderly organization collapses and the water molecules motility past each other and actually get closer together as liquid water.

   Project the image Ice and H2o

   Ask students

   How did the move and arrangement of the h2o molecules change as the ice melted?

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

5. Compare the motility and arrangement of the molecules of a substance (not h2o) for each state of matter.

   Project the image States of Matter.

   Explicate that the diagram illustrates the motion and arrangement of atoms or molecules in a single substance (not water) when it changes between a solid, liquid, and gas.

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

   Projection the prototype States of Water.

   Tell students that the motion of water molecules in each state of affair is similar to what happens for most substances. Adding energy increases the motion of the molecules and causes them to move further apart. Removing energy decreases the move of the molecules and causes them to move closer together. But, water does something very unusual when it freezes to get ice. The molecules, which were moving closer and closer together, motility further autonomously equally they organize themselves into the open band design shown below for ice. This is why ice expands when information technology freezes.

   Enquire students:

   Read more nigh free energy and land changes in the instructor groundwork section.

   How are the country changes of h2o similar to and dissimilar from the state changes in most other substances?

   For water or any other substance, molecular movement increases when free energy is added and decreases when energy is removed. The primary divergence betwixt water and other substances is the arrangement between 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 nigh other substances are closer together than they are every bit a liquid.

7. Have groups employ their water molecules to model freezing, melting, evaporation, and condensation.

   Process

   Project the image Water ice.

   Have each group accommodate their water molecules into a vi-sided ring of ice. Ask students to handle their models gently because they will need them for other lessons.

   Water ice Melts

   Accept students use their models to represent what happens when ice melts. Point out that the water molecules are closer together than they were as ice. Students could bear witness the h2o molecules moving past each other.

   Water Evaporates

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

   Water Vapor Condenses

   Have students use their molecules to model what would happen if h2o vapor was cooled enough to cause it to condense. Students should evidence the water molecules in the air slowing down and joining together but still moving by one another as liquid water.

   Collect the water molecules. These models will exist used again in Chapter 5, Lesson 1.

8. Practice a sit-in to compare the melting of regular ice and dry out water ice.

   Let students know that dry ice is frozen carbon dioxide gas. Carbon dioxide gas must be very cold in gild to become a solid (near −78 °C or −109 °F).

   Preparation

   Y'all will need some dry ice for this demonstration. If you lot cannot become any dry out ice, show the video Dry Ice.

   Question to investigate

   Does dry water ice cook the way regular water ice does?

   Materials

   • Ice
   • Dry ice
   • Brown paper towel
   • Cold water
   • Hot water (about l °C)

   Procedure

   1. Place a piece of dry ice and a piece of regular ice on a brown paper towel.

   Expected results

   In a short corporeality of fourth dimension, the ice volition begin to melt and the newspaper towel effectually the ice will become wet and darker. The paper towel around the dry ice will stay dry out and will not get darker. If you notice a pocket-sized dark spot on the paper towel about the dry out ice, information technology is possible that water vapor from the air condensed on the dry ice and melted onto the paper towel.

   If students see misty white fog coming from the dry water ice, let them know that it is non 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 water ice and the cold carbon dioxide gas. The fog tends to drift downwards because it is carried past the carbon dioxide gas, which is more dense than the air effectually it.

9. Discuss pupil observations and introduce the idea that some substances can change directly from a solid to a gas.

   Ask students:

   Do regular ice and dry ice cook in the same way?

   No. The regular water ice changes to a liquid, which yous see on the brown paper towel. The dry water ice does non seem to change to a liquid.

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

10. Evidence students what happens when dry ice is placed in h2o.

    Place a piece of dry ice in h2o and then add a lilliputian dish detergent or bear witness the video Dry Ice in H2o.

    Expected results

    Bubbles will grade and a misty white fog will be produced. Since the h2o is much warmer than the dry ice, energy is transferred from the h2o to the dry ice, causing it to change from a solid to a gas and bubble through the h2o. After detergent is added, a mound of bubbles will grade.

    Students will be curious most 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 and then condenses. This causes fog within the bubbles which escapes when the bubble pops.

    Ask students:

    Yous saw that the dry out ice sublimates very quickly in water. What could yous do to make dry ice sublimate even faster?

    There are several means to brand dry ice sublimate faster. I option is to put the dry ice in hot h2o.

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

    Expected results:

    Much more fog will exist produced from the cup with hot h2o.

    Tell students that more fog is produced when dry ice is placed in hot water considering the transfer of free energy and sublimation happens faster. This causes the fog to be produced at a faster rate.

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