Lesson 1.4: Moving Molecules in a Solid - American Chemical Society (2024)

Youtube ID: JPj8pgAnK4Y

Key Concepts

• In a solid, the atoms are very attracted to one another. The atoms vibrate but stay in fixed positions because of their strong attractions for one another.
• Heating a solid increases the motion of the atoms.
• An increase in the motion of the atoms competes with the attraction between atoms and causes them to move a little further apart.
• Cooling a solid decreases the motion of the atoms.
• A decrease in the motion of the atoms allows the attractions between atoms to bring them a little close together.

Summary

Students will see a demonstration with a metal ball and ring showing that heat causes atoms to spread a little further apart. They will also see that cooling a solid causes the atoms to get a little closer together. The same rules they discovered about liquids also apply to solids.

Objective

Based on their observations students will describe, on the molecular level, how heating and cooling affect the motion of atoms in a solid.

Materials for the Demonstration

• Ball and ring designed specifically for this demonstration
• Bunsen burner for heating the ball
• Room temperature water (to cool the ball)

Notes about the materials

The metal ball and ring are available from Flynn Scientific (AP9031) or other suppliers.

About this Lesson

The solid explored in this lesson is a metal. Metal is composed of individual atoms instead of molecules like in the water and alcohol students learned about in Lessons 1–3. Although atoms and molecules are different, we will represent atoms the same way we represented molecules, using a circle or sphere. This simple representation will help students focus on the motion and position of the particles when they are heated and cooled.

Ask students:

• What do you know about the molecules in a liquid?
  Be sure students understand that the molecules in a liquid are attracted to each other but are able to move past each other.
• How does heating or cooling affect the speed of the molecules and the distance between them?
  Heating speeds up the motion of molecules and cooling slows them down. We’ve also seen that speeding the molecules up makes them move a little further apart and slowing them down allows them to move a little closer together.

Ask students if these statements also apply to solids:

• Do you think the atoms in a solid are attracted to each other?
  Students will probably realize that the atoms of a solid are attracted to each other. Explain that this is how a solid stays together.
• Do you think heating or cooling a solid might affect the motion of the atoms?
  Students should realize that if you heat a solid, the atoms or molecules move faster and move further apart. If you cool a solid, the molecules move more slowly and move a little closer together.

Explain that the little balls represent the particles of a solid, in this case the atoms in a metal. Although atoms and molecules are different, this same simple model of balls is used for both. Let students know that for now, they will use circles or spheres to represent atoms and molecules, but eventually they will use a more detailed model. Tell students that they should focus on the motion of the molecules, how they interact, and their distance from one another.

Show the molecular model animation Particles of a Solid.

Point out the following about solids:

• The particles (atoms or molecules) are attracted to each other.
• The particles (atoms or molecules) vibrate but do not move past one another.
• The solid retains its shape.

Show the molecular model animation Comparing Solid and Liquid.

Click on both tabs and make sure students notice the differences in the movement of the atoms and molecules.

• The atoms in a solid are so attracted to each other that they vibrate and don’t move past each other.
• The molecules of a liquid are attracted to each other but move more freely and past one another.

Give each student an activity sheet.

• Lesson 1.4 Student Activity SheetPDF|DOCX|Google Doc
• Lesson 1.4 Activity Sheet AnswersPDF|DOCX|Google Doc
  

Download the student activity sheet, and distribute one per student.

All Downloads

The activity sheet will serve as the “Evaluate” component of each 5-E lesson plan. The activity sheets are formative assessments of student progress and understanding. A more formal summative assessment is included at the end of each chapter.

Students will record their observations and answer questions about the animation on the activity sheet. TheExplain It with Atoms & MoleculesandTake It Furthersections of the activity sheet will either be completed as a class, in groups, or individually depending on your instructions. Look at the teacher version of the activity sheet to find the questions and answers.

Question to investigate
How do heating and cooling affect a solid?

Materials for the presenter

• Ball and ring designed specifically for this demonstration
• Bunsen burner for heating the ball
• Room temperature water (to cool the ball)

Point out that when metal is heated, the atoms move faster and move slightly further apart. This makes the heated ball expand, which prevents it from passing through the ring.

Point out that when the metal is cooled, the atoms move slower and move slightly closer together. This makes the cooled metal ball get slightly smaller so that it fits through the ring again.

Give students time to complete the questions and drawings on the activity sheet about heating and cooling the metal ball.

Project the image Molecules in a Room Temperature and Hot Metal Ball.

Help students draw circles to represent the atoms in the ball at room temperature and after it is heated. Have students write captions describing the speed and distance of the atoms in each picture.

Ask students:

• Knowing what you do about how solids act when they are heated and cooled, why do you think they put flexible connections in the surface of a bridge?
  Students should realize that if the bridge is hotter than the land around it, it should be able to expand a bit without breaking. If it is colder than the land around it, it should be able to contract a bit without breaking.

After the class discussion, have students write their own response to the question about flexible bridge connections on the activity sheet.

For Students

• Lesson 1.4 Student Activity SheetPDF|DOCX|Google Doc

For Teachers

• Lesson 1.4 Lesson PlanPDF|DOCX|Google Doc
• Lesson 1.4 Activity Sheet AnswersPDF|DOCX|Google Doc

Interactive Lesson Modules

• Lesson 1.4 Online AssignmentsGoogle Form

Lesson 1.3: The Ups and Downs of Thermometers

Lesson 1.5:Air, It's Really There