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You Can't See Me!
The students will heat and cool a volume of air to understand that particles of air are always around us, too small to be seen in most cases, expand when heated and contract when they are cooled.
- Ask students to write the following title in their journals: What is a gas?
- Allow students 5-7 minutes to respond in writing to the prompt.
Explicit instruction/Teacher modeling(5 minutes)
- Have students compare their answer to the people sitting next to them in class.
- Ask for 2-3 volunteers to share their answer.
- At this point, don't tell students if they are right or wrong. After the guided practice, students will generate their own working definition for the term gas.
Guided practice/Interactive modeling(15 minutes)
- Tell students to trap a volume of air in each bottle and secure the lid. Ask them some questions to start the lesson: What is in the bottle once the lid is on it? How do they know?
- If a student hasn't done so already, explain that they've trapped air in the container. Tell the class that air is always around us, and always moving.
- Remind students that if there is a volume of air in the bottle, then that air has taken the shape of its container (the bottle). Tell them that this is a property of gases.
- Finally ask students what would happen to this defined volume of air if you heated it up or cooled it down? Take a few responses or advise students to just think about it for a minute.
Next, arrange students into groups or pairs.
- Give each pair or group of students the materials they need for the lab.
- Allow them to touch, feel, and discuss when and where they have seen any of the materials. This allows them to access their prior knowledge.
- Direct students to put on their goggles for safety.
- Next, ask students to get hot and cold water and place them in the beakers. Make sure they record the temperature of both hot and cold water.
- Once they are at their ideal temperatures (cold water: 5 degrees C; hot water: 65-70 degrees C) students should remove the top from each bottle, and dip them both in the bubble solution.
- Have them place one of the bottles (bottom side down) in cold and the other in hot. Hold it down.
- Ask the class to record their observations, or things they notice, and discuss them with their partner or group.
Independent working time(15 minutes)
Your students should repeat the following steps, independently:
- Students should keep their goggles for safety.
- Students get hot and cold water and place them in the beakers.
- They take and record the temperature of both hot and cold water.
- Once they are at their ideal temperatures (cold water: 5 degrees C; hot water: 65-70 degrees C) they should remove the top from each bottle and place a balloon over the mouth of them both.
- They should place one of the bottles (bottom side down) in cold and the other in hot. Hold them down in the water.
- Have students record their observations.
- Remove both bottles from their respective beakers and quickly put the bottle that was in the hot water into the cold water. Have students record their observations, and discuss with their partners or group.
- Enrichment: For students who need more of a challenge, provide the topic of the experiment only (i.e. kinetic energy of gas). Have students conduct research on the topic and create their very own testable question and experimental design.
- Support: The question/problem/answer should be well-defined and given in advance for students who need extra support. Provide assistance during steps of the experiment. Alternatively, give these students a handout with the lab instructions on it, and help them as needed.
- Use an interactive whiteboard to review important terms and summarize student creation of content vocabulary.
Each student should create a CER (claim, evidence, and reasoning) lab report using content vocabulary. The CER is a format used to write about science.
- Claim: a conclusion about a problem
- Evidence: scientific data that is appropriate and sufficient to support the claim
- Reasoning: a justification that shows why the data counts as evidence to support the claim and includes appropriate scientific principles
Review and closing(5 minutes)
- Once complete, have students share their CER with the class.
- Students should be required to use content specific vocabulary. For instance, students shouldn't say that the balloon "got bigger." If they do, explain that when the balloon gets bigger, this is called expansion.
- Define the term contraction as "getting smaller," or the opposite of expansion.
- Review the definition of gas with your class: a form of matter, or something that has mass and takes up space. This matter is composed of tiny particles that you may or may not be able to see, take the shape of its container, expands when heated and contracts when cooled.