• Students will use adjectives to describe phases of matter.
• Students will follow a procedure to create Oobleck.
• Students will provide rationale for the phase they use to describe Oobleck.

Matter can change phase when energy is added or taken away. In this lesson, students will explore the three main phases of matter: solid, liquid and gas. They will explore what is happening during a phase change and how atoms behave in each phase. Students will be given a phenomenon and be asked to explain what phase change they see happening. Finally, students will explore a material that does not classify as one of the three standard phases.

Teacher Preparation

• Premeasure 30 ml water in a cup for each student.
• Premeasure 40 g of cornstarch in a separate dish or condiment cup.
• Provide each student with a toothpick for stirring.
• Lay a puppy pad or paper towels on the desks for easy clean up.

Lesson Plan

Start by showing students the phenomenon video: What Changes Do You See? Show the video a few times and then proceed to the Phases of Matter Slide Show. Allow time for the students to record their observations and answers to the questions in the Phases of Matter Lab Notebook. If possible, try the same demonstration in your classroom using dry ice and a scientific-grade beaker of water.

Discuss what is happening with the atoms inside each of the phases. Solids retain their shape, liquids take the shape of the container and gases leave the container.

Move Activity
Ask students to act like an atom in each phase. A solid would stand perfectly still, a liquid would flow back and forth, and a gas would be full of energy and move around. Have students return back to a solid state to continue the lesson.

Discuss which phases students observed in the video.

Discussion
This video shows dry ice sublimating into a gas. Dry ice is frozen carbon dioxide, so the gas is carbon dioxide. Students may identify the white mist as gas but may need help making the connection to the bubbles coming off the ice.

Using the Phases of Matter Slide Show, discuss the phase changes with students. Encourage students to provide examples of phase changes. For example, ice melting in a glass or steam coming from a teapot. (If you have ice and a cup of water, you could demonstrate melting.)

Move on to the slide entitled Skipping Phases (slide 10). Allow students time to draw or write about anytime they have seen matter skip a phase. (Most students will have experience with frost on the window.)

Point out that there are terms for skipping phases called deposition and sublimation. Deposition is the process of going directly from a gas into a solid phase. Sublimation is the process of going directly from a solid into a gas phase.

Refer back to the dry ice in water video. Allow students to discuss what is causing the gas. Is it evaporation or sublimation? It is important that students provide evidence for their explanation. The most obvious evidence is that there is a gas bubble surrounding the dry ice, which means the dry ice is producing gas. When water evaporates, there are bubbles on the bottom surface where the heat is located. That is not the case for this video.

It is important for students to understand that not all matter can be classified as a solid, liquid or gas. In fact, scientists have identified 12 states of matter. The following experiment will allow them to experience matter that does not fit the three standard phases.

Experiment Time!

Make sure you've answered questions in the Phases of Matter Lab Notebook. Next, ask students to add the cornstarch to the water and mix (slide 13). As they mix, have them explain the texture. Is it a solid or liquid? Answer: It is actually a non-Newtonian fluid, which is liquid most of the time, but when pressure is added, it becomes a solid.

The Sanford Connection
At Sanford Research, scientists use dry ice to keep cell samples cold enough to ship across the world. We can use frozen blood samples to help us better understand and treat disease! Biobanks play a crucial role in biomedical research by providing access to biological specimens linked to the patient donor's health history. The BioBank at Sanford Imagenetics is a collection of biological samples and health information. Learn more here.

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