Summary

In this lesson, students will identify properties of different states of matter and then work in groups to model the molecular arrangement in water as a solid, liquid, and gas. This lesson will also help students understand that the change in state is a physical change and how the solid state of water has unique properties.

Grade Level

Elementary School, Middle School

NGSS Alignment

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

• 5-PS1-1: Develop a model to describe that matter is made of particles too small to be seen.
• MS-PS1-1: Develop models to describe atomic composition of simple molecules and extended structures.
• 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.
• Scientific and Engineering Practices:
  • Developing and Using Models
  • Constructing Explanations and Designing Solutions

Objectives

By the end of this lesson, students should be able to:

• Model the molecular arrangement in water as a solid, liquid, and gas.
• Identify change of state as a physical change, not a chemical change.
• Identify the freezing point and boiling point of water.
• Identify properties of solids, liquids, and gases.

Chemistry Topics

This lesson supports students’ understanding of:

• States of matter
• Phase Changes
• Boiling Point
• Melting Point
• Physical change

Time

Teacher Preparation: 15 minutes
Lesson: 60 minutes

Materials

• ½ sheets of computer or construction paper
• Markers
• Masking tape
• Optional Materials:
  • Hot Plate with Boiling Water
  • Room Temperature Water
  • Cold Water
  • Ice
• Signs for different stations:
  • 100⁰C Boiling Point
  • 22⁰C Room Temperature
  • 4⁰C Almost Freezing
  • 0⁰C Freezing Point/Melting Point

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.

If using a hot plate to model boiling point:

• Exercise caution when using a heat source. Hot plates should be turned off and unplugged as soon as they are no longer needed.
• An operational fire extinguisher should be in the classroom.

Teacher Notes

• This lesson is designed for grades 4-6.
• Prior to beginning the kinesthetic aspect of this activity, it is important that students have a basic understanding of the three states of matter and that a change in state is a physical change. You may want to show students a video or animation that gives a basic explanation of the three states of matter for water and how heating and cooling lead to state changes.
• Groups for this activity should be larger than your typical groups. Separate the whole class into 4 groups, as there will be 4 stations to which each group will rotate. Ideal group size = 6-8 students.
• Students will spend about 5 minutes at each station, arranging themselves and recording observations for the station that they experienced. After the 5-minute period, have the groups rotate clockwise.
• Labels and directions for each station:
  • Station 1: Water Vapor: Spread as far apart as you can and move as quickly as possible within your space.
  • Station 2: Liquid Water at Room Temperature: Move closer together than a gas and slow down. Move your arms like you think liquid moves.
  • Station 3: Liquid Water at Almost Freezing: Move closer together than a liquid at room temperature.Continue moving your arms like a liquid.
  • Station 4: Frozen Water (Solid Ice): Spread out to fill the box and lock arms with your group members in a regular pattern.
  • If students aren’t yet familiar with (or need a reminder of) various important temperatures (such as water’s freezing point, 0°C; boiling point, 100°C; or room temperature, 22°C), you can include these with the directions for the stations or add them to the background information to help students complete the handout.
    
• In an ideal situation, you can have a volunteer or teacher’s aide consistently monitoring the Boiling Point station, operating the hot plate to boil water. Students will be able to observe evaporation (liquid water changing to water vapor) at this station prior to modeling the molecular arrangement of water molecules in a gas. If you do not have a helper for this activity, you may either decide to use this part of the activity as a demonstration prior to the activity or personally stay at this station throughout the activity.
  • The downside of remaining at one station is that it will inhibit you from gauging understanding at the remaining stations. However, you do not want to leave students unattended at this station with the boiling water, as molecules move freely and quickly in a hot gas, and this could cause an accident.
• The use of actual examples of the different states of water is optional, so you may consider using them in a separate demonstration or lesson. The benefit of examples with this particular activity is that students can quickly connect the molecular arrangement to the real world state of water. If you have a particularly large class of students, you may also consider making a 5^th station.
• You will need to set up your signs in 4 corners of your classroom and tape off a square block in each of those stations. The students will arrange themselves as molecules of water as a solid, liquid at room temperature, liquid in almost freezing water, and a solid inside each of the boxes. The box for gas should be larger than liquid for space to move around.
  
• This visual and descriptions below can help for comparing water’s states of matter:
  

• Station 1: See the “Water vapor” diagram. Water molecules at greater than 100°C (boiling point). Molecules are spaced far apart and move very quickly.
• Station 2: See the “Warm water” diagram. Water molecules at room temperature, about 22°C. Molecules are closer together than in a gas and cannot move as quickly.
• Station 3: See the “Cold water” diagram. Water molecules are almost freezing, 4°C. As molecules get colder, they move more slowly and get even closer together, making them denser. This is why they sink to the bottom. Warm water rises, and cold water sinks. In most substances other than water, the solid state is most dense.
• Station 4: See the “Ice” diagram. If water molecules were like most substances, it would sink in its solid state, because that’s when its molecules would be closest together, but it doesn’t. Ice floats in liquid water meaning that its molecules are not closer together but farther apart. They crystallize in a regular pattern with the positive side (hydrogen) attracted to the negative side (oxygen).