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ACTIVITY in Phase Changes, Molecular Motion. Last updated January 29, 2024.

Summary

In this activity, students will explore how particles that make up matter are in constant motion. The students will use an online PhET simulation to compare the ways that atoms and molecules move in samples of solids, liquids, and gases. This activity will help students improve their understanding of the particle level.

Grade Level

Middle School

NGSS Standards

This activity will help prepare your students to meet the performance expectations in the following standards:

  • MS-PS1-4 Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.

Objectives

By the end of this activity, students should be able to

  • Draw and identify a model that represents matter in the three states: solid, liquid, gas.
  • Use correct terminology to describe the phase changes of matter (melting, freezing, evaporating, boiling, condensing)
  • Predict the effect of change in temperature on a substance’s state of matter.
  • Relate different phases of matter to the relative energy level of the particles.

Chemistry Topics

This activity supports students’ understanding of:

  • States of Matter
  • Molecular Motion
  • Phase Changes
  • Physical Changes

Time

Teacher Preparation: 10 minutes

Lesson: 50-75 minutes

Materials

  • Computer with internet connection
  • Atoms in Motion Student Handout

Safety

  • No specific safety precautions need to be observed for this activity.

Teacher Notes

Prior to the simulation:

  • Review the three states of matter using the following open-ended questions:
  1. “What are the states of matter?”
  2. “What are the molecular structures for each state of matter?”
  • Assign student the prelab questions as a review, and use them to drive a class discussion with your students.
  • Remind students that, although we cannot see molecular motion with our eyes, molecules and atoms are always moving.
  • Use some of the student’s examples to discuss how much heating or cooling was needed in particular situations.
  • Help students to understand that heat and temperature are not the same, although they are also used interchangeably in everyday language. Heat explains the transfer of energy between two substances. On the other hand, temperature describes the average motion of the particles within a substance.
  • This activity will focus on the concept that matter can change states when enough heat energy is added or removed from it. A change in pressure can also result in a change in state. A change of state or phase change is a physical change from one state of matter to another.
  • The phase changes that will be examined in this activity:
    • Melting: the transformation of a solid to a liquid, occurs when heat is added to a solid.
    • Freezing: the transformation of a liquid to a solid, occurs when heat is removed from a liquid.
    • Evaporation: the transformation of a liquid to a gas, occurs when heat is added to a liquid.
    • Condensation: the transformation of a gas to a liquid, occurs when heat is removed from a gas.
  • Vocabulary Terms: Use the following vocabulary during the activity so that students become familiar with these words. Hopefully by the end of the activity the students will be able to provide the definitions to these vocabulary terms in their own words.
    • Matter: Anything that has mass and takes up space
    • Mass: The amount of matter that makes up a substance
    • Solid: Matter that has a definite shape and volume
    • Liquid: Matter that has a definite volume, but takes up the shape of its container
    • Gas: Matter that spreads to fill up any volume, taking the shape of its container
    • Phase Change: A change from one state (solid, liquid, gas) to another
    • Condensation: The process where a gas turns into a liquid
    • Evaporation: The process where liquid turns into a gas
    • Freezing: The process where liquid turns into a solid
    • Melting: The process where solid turns into a liquid
  • Use the PhET Simulation States of Matter: Basics updated version (not JAVA) this version works fine on most platforms. However, as with any technology based activity, check that the simulation works properly on your student devices before use.

For the Student

Lesson

Background

In this activity you will develop your understanding about how and why matter exists in three forms on Earth (solid, liquid, gas) and what causes matter to change from one form to another. You will explore how particles behave in the different states of matter. Then you will discover how thermal energy effects the interactions and behavior of these particles in the three states of matter. You will also observe that particles are in constant motion and that this motion changes with the addition of or removal of thermal energy.

Prelab Questions

  1. What are the states of matter?
  2. Have you ever seen a solid turn into a liquid? Provide an example:
  3. Have you ever seen a liquid turn into a gas? Provide an example:
  4. Have you ever seen a liquid turn into a solid? Provide an example:
  5. Have you ever seen a gas turn into a liquid? Provide an example:

Driving Question

What is the effect of thermal energy on the atoms/molecules in a sample of matter?

Make your Claim:

Exploration

  1. Click on the link for the PhET Interactive Simulation: States of Matter Basics
  2. The below screen will open and you will need to click on “States”.

  1. Now you should see different types of atoms and molecules to explore on the upper right-hand side. There is neon, argon, oxygen, and water.

  1. Under the Atoms and Molecules header, there are boxes, each marked “Solid, Liquid, Gas”, click on one and watch as the atoms and molecules change to represent that state of matter.
  2. First click the “neon” button, then the solid button and increase the heat and observe what happens to the particles. Then decrease the heat and observe what happens to the particles. Observe the temperature as well.
  3. Record your observations for Neon in the data table below.
  4. Repeat step 4 for the argon, oxygen, and then water.
  5. Change the state of matter and repeat step 4 for each state.

Observations: Complete the table for Neon

State of Matter

Sketch 10 atoms the way they appear

Does the group of atoms have a fixed shape?

YES/NO

Are the atoms touching each other?

YES/NO

Are the atoms vibrating?

YES/NO

Are the atoms changing location?

YES/NO

Rank the speed of the particles

1=slowest

2=mid

3 =fastest

Solid

Liquid

Gas

Analysis

  1. Choose oxygen from the Atoms & Molecules list and then choose solid as the state of matter. Record the temperature shown:
  2. Describe the motion of the oxygen molecules in complete sentences. What are they doing? How fast are they moving? How are the molecules arranged?
  3. Heat the oxygen molecules until the temperature is around 74 K or -200°C. How did this affect the motion of the oxygen molecules? Explain in complete sentences.
  4. Did the oxygen change state as you heated the molecules? Explain how you know in complete sentences.
  5. Heat the oxygen molecules until the temperature is around 194 K or -80°C. How did this affect the motion of m? Explain in complete sentences.
  6. Now choose water as the molecule type and add heat to the system by adjusting the heat at the bottom of the simulator. Once the temperature is at its highest point, make a drawing and write your observations about the behavior of the molecules.
Drawing Observation
  1. Now remove heat from the system by controlling the heat at the bottom of the simulator. Once the temperature is at its lowest point, make a drawing and write your observations about the behavior of the molecules.
Drawing Observation

Conclusion Based on your data, what can you conclude about the different states of matter and how each atom or molecule changed as the temperature changed? Write your conclusion in CER (Claim, Evidence, Reasoning) format.

Re-read your conclusion:

  • Did you restate your claim?
  • Did you include all your evidence?
  • Did you end with your reasoning?