States of Matter (lesson five of eight)
Grade level(s):Elementary School (K-5), Grade 3, Grade 4, Grade 5
Subjects(s):Chemistry, Physical Science
Topic:Matter and Energy
Adding or removing energy causes changes in states of matter.
solid, liquid, gas, evaporation, condensation, melting, freezing, sublimation, control, variable, experiment, test, prediction
What you need:
ice, dry ice, plastic snack bags, beaker, stove, liquid nitrogen, rose (or other fragile item), ingredients for ice cream (cream, sugar, vanilla, chocolate chips)
whole class and independent
Students investigate the difference between ice and dry ice, and review the concept of control and variable. The scientists demonstrate condensation, sublimation, and freezing with a series of object lessons.
Students should be familiar with the different forms of energy, know that they can be interconverted, and that you can design an experiment with controls and variables to test a prediction.
Learning Objectives 1) Learn the difference between solid, liquid, and gas. 2) Understand that states of matter are changed by adding or removing energy (and what this means on the molecular level) 3) Reinforce scientific method – testing a hypothesis with an experiment. Language Goals 1) Introduce the terms solid, liquid, gas, evaporation, condensation, melting, freezing, sublimation using word wall. 2) Reinforce hypothesis and energy terms.
Caution: liquid nitrogen is extremely dangerous and should only be handled by adults wearing appropriate safety equipment (coats, gloves, and goggles). A 10-foot radius should be enforced in case any liquid nitrogen spills. Additionally, student should be allowed to touch the dry ice with the forewarning that it will BURN them if they keep their hand on it.
Lesson Implementation / Outline
10’ An instructor introduces states of matter by pointing to a glass that is half full of water and explaining that the other half is full of air. Discuss the states of matter and describe how energy can change the states of matter. Discuss what happens to molecules when heat is added or removed from the system. Have kids give examples of solids, liquids, and gases and write these on the board.
15’ Introduce experiment: Shows ice in one bag and dry ice in the other bag. Reinforces the idea of a hypothesis, and testing a hypothesis with an experiment. As a class, students make a hypothesis about how the state of matter will change as the ice warms at room temperature. Hand out regular ice to each pair.
15' First students observe their bags filled with regular ice. They melt the ice in their bags. Meanwhile, go over control and variable. Next, all the bags are collected and the class discusses what happened. Second, they are quickly given bags filled with dry ice. Students observe and describe what happens. Note: some of the bags will pop after a time. Explain that the dry ice is being turned from a solid into a gas, through a process called sublimation. (Instructors Note: carbon dioxide is a colorless gas, the cloudy gas seen around the dry ice is the water molecules in the air condensing into steam)
10’ Condensation and Evaporation Demonstration: Describe evaporation and condensation. One instructor boils water to demonstrate evaporation and another holds saran wrap over the water vapor to illustrate condensation. Add all of these words to the word wall. For a dramatic effect, throw the dry ice into the warm water. The bubbles (if the water has stopped boiling) are evidence of the dry ice being converted into carbon dioxide gas.
10’ Liquid nitrogen introduction: Return the half full glass of water and explain that nitrogen comprises most of the air we breathe. Explain that under very high pressures this gas can be a liquid. Explain that liquid nitrogen is extremely cold and could potentially burn the students. Safety is of utmost importance. Ask the class what will happen to a balloon full of air when it is taken to extreme cold, referring to molecules loosing heat energy and moving more slowly. Freeze something solid (like a rose) and then smash it.
20’ Liquid nitrogen ice cream: Here the cream is going from liquid to solid. Students are asked if ice, dry ice or liquid nitrogen will turn cream into ice cream. Deliciousness ensues.
Extensions and Reflections
This was our crazy fun lesson. We didn't want the students to have to write anything. We just wanted them to have fun, introduce the states of matter to them, and have them review control and variable. We rewarded them with the ice cream. However, to make sure the students understood everything in that lesson, it would probably be useful for the teachers to go back and review the key concepts (solid, liquid, gas and the terms that describe how they transition from one state to another).