Chemical and Physical Changes Lab Stations
Lesson 3 of 9
Objective: Students will be able to cite evidence in order to determine if a reaction as a chemical or physical change and identify that the properties of the reactants and products of a reaction are different.
In this lesson, students go through a series of 12 quick lab stations in order to practice identifying reactions as chemical or physical changes. At each lab station, students not only identify the signs of a chemical change, but they also read reactant and product descriptions in order to identify changes in chemical and physical properties that occurred. Each station is quick, fun, and very specific to to standard MS-PS1-2!
This lesson is designed to connect to the following NGSS and Common Core Standards:
MS-PS1 - 2 Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
CCSS.ELA-LITERACY.RST.6-8.1 Cite specific textual evidence to support analysis of science and technical texts.
CCSS.ELA-LITERACY.RST.6-8.3 Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.
CCSS.ELA-LITERACY.WHST.6-8.1.B Support claim(s) with logical reasoning and relevant, accurate data and evidence that demonstrate an understanding of the topic or text, using credible sources.
CCSS.ELA-LITERACY.WHST.6-8.9 Draw evidence from informational texts to support analysis, reflection, and research.
Science and Engineering Practices:
The NGSS asks that students develop and/or use a model to predict and/or describe phenomena (SP2). In doing this, students should construct, use, and/or present an oral and written argument supported by empirical evidence and scientific reasoning to support or refute an explanation or a model for a phenomenon. When students look for patterns in data to identify the signs of a chemical change based on their qualitative observations, they do just that! (SP7) Therefore, this also means that students analyze and interpret data to provide evidence to describe phenomena. (SP4)
At each lab station, students use patterns in evidence to identify each reaction as chemical or physical. Students thus realize that patterns can be used to predict phenomena. (Patterns)
Ask students, "What are you going to learn today?" Students should respond by saying that they will be answering the Essential Question, "How do particles combine into new substances? And, what evidence can show how the physical and chemical properties of the substances change?" This EQ is posted on my board and on the student's Chemistry Unit Plan.
Explain to students that we will again be working with Skill CH.5 Notes Page and True and False Statements of the Chemistry Unit Plan, "I can provide evidence to show if a reaction is a chemical or physical change." (My students have already been introduced to the concepts involved in identifying reactions as chemical or physical in previous lessons.) Have students turn to their unit plans and silently read the skill. After reading the skill, students rank their current level of mastery on a scale of 1 to 4 (4 being mastery). Students in my room have already assessed themselves in the lesson prior to this; this would be an opportunity for the student to change their number if they felt their level of mastery had increased after the previous lesson.
In my classroom, students frequently self-assess their level of understanding on each skill in the unit as we go. As you can see from the image below, this student ranks has continually updated his level of mastery on each skill has his learning has developed.
Students in my class have already had an introduction to the differences between chemical and physical reactions. My students have already worked through the Skill CH.5 Notes Page and True and False Statements when they complete these labs.
For a look at all the lessons that have led my students to this point and where we go from here check out the lessons in these units:
Physical Properties: Molecular Arrangement and Phase Changes: Focuses on Skills 1 - 4 of the Chemistry Unit Plan
This unit is designed to answer the Essential Question, "How do particles combine into new substances? What evidence can show how the physical and chemical properties of the substances change?". It particularly focuses on types of matter, physical properties, phase changes, and factors that affect physical properties. This unit's purpose is so much more than just the content, however. It's focus is scientific literacy. It stresses group discussion, discourse and utilizing text references when engaging in argument. Students utilize reading, writing, and speaking strategies in order to develop scientific literacy. It's scientific literacy immersion!
Chemical Properties and Reactions: Focuses on Skills 4 - 6 of the Chemistry Unit Plan.
This unit is also designed to answer the Essential Question, "How do particles combine into new substances? What evidence can show how the physical and chemical properties of the substances change?". This unit focuses on chemical properties and chemical reactions. Students analyze evidence and property changes that allow them to distinguish between chemical and physical reactions. In addition, students investigate the Law of Conservation of Mass as they look at how bonds are broken and formed in chemical reactions. This unit is full of hands on labs and station rotations that will engage any middle school student in chemistry!
In the previous two lessons (Chemical Reactions Un-Notes and Chemical Physical Group Challenge), students have been developing an understanding of the difference between a chemical and physical reaction. Before beginning the lab stations, review some of the important concepts with your students.
Topics to Review:
1. What is the biggest different between a chemical and physical reaction?
Students should respond with the idea that in a chemical reaction something new is produced. Bonds are broken and formed creating something new. However, a physical change does not produce a new substance.
2. What are some pieces of evidence or signs that a chemical reaction may be occurring?
Students should identify color change, temperature change, pH change, gas production and solid formation (or precipitate).
3. What is meant by "solid formation" or a "precipitate"?
Students should identify that a precipitate is formed when two solutions are combined producing a new solid.
4. What occurs to the properties of the reactants and products during a chemical reaction?
It is important that students connect that the products in a chemical reaction will have new chemical and physical properties than the reactants. Some students think that the products will simply be a "mix" of the original properties rather than realizing the properties of the products are independent of the properties of the reactants.
5. What occurs to the properties of the reactants in a physical reaction?
Students should identify that the physical properties of the substances change during a physical reaction while the chemical properties do not change. Some students get the idea that only chemical reactions can change the properties of a substance; however, it is important that students realize that physical reactions change the properties of substances as well.
After reviewing, talk through with the students how to complete the chart as they complete the lab stations. Take them through the steps they will complete at each lab station.
Student Procedure for Each Lab Station:
- You will have 5 minutes to work through each station. A timer will be projected so that you can watch your time. You must be efficient! (Honestly, for the first 2 lab rotations, the students are going to go over the allotted 5 minutes. Having the timer projected will keep them focused, though. After they get the routine, stations will move at 5 minutes per station.)
- It is imperative that you read the procedures carefully at each lab station. Each station has a sign with the procedure along with a description of the properties of the substances involved in the reaction. (Have students look at their Reactant and Product Property Description page and let them note that these descriptions are also included there.) Before completing the procedure, identify 2 physical and 2 chemical properties noted in the property description page.
I usually talk them through the first row because this can be challenging for middle school students. I have them read the description for Station 1 which states:
Crackers are brown substances that crumbled when pressure is applied to them. Their surface is bumpy. Crackers are made up of lots of different chemicals that are made with ionic and covalent bonds. These chemicals break down when surrounded by stomach acid.
I then have the students look in the right hand column at the list of chemical and physical properties. I ask them which of these properties were described here. Students may offer things such as color, texture, reactivity with acid and ionic bonds. Ask them to write 2 physical properties that were described in the first column and 2 chemical properties in the 2nd column. Emphasize that they cannot choose "random" properties at each station. They must pull the properties from the text!
3. Read and follow the procedure and pay attention to any safety precautions listed. Make careful observations during the reaction.
4. In the third column, determine whether you feel the reaction you observed was a chemical reaction, physical reaction, or both.
5. In the last column "Evidence of a Chemical Change", if you choose physical reaction, there is no need to write anything. However, if the reaction is chemical or "both", you must include the evidence that lead you to that conclusion. The 5 signs of a chemical change are also included in the right column of the lab sheet. Remember to list all of the evidence you can! For some stations there will be three or four pieces of evidence that indicate it is a chemical reaction. It is important that you include them all!
6. Clean up your station. Do not rotate until indicated by the teacher.
Have students work in groups of 2 - 4. Assign each group a lab station to begin with. Put the timer on your projector or write the time on the board that students will be rotating to the next lab station.
Stations 1, 2, and 3
Station 1: Star Quality
- Wash your hands.
- Take one of the crackers.
- Chew and swallow it.
Station 2: The Amazing Bubbling Ribbon
- Wrap a small amount of magnesium ribbon around your pencil and cut it.
- Using a graduated cylinder, measure about 4 eye droppers full of copper II sulfate and pour it into the sandwich bag. (It doesn’t have to be exact.)
- Drop the coiled magnesium ribbon into the baggie. DO NOT PUT YOUR PENCIL IN THE BAG! ONLY THE RIBBON!
- Close the sandwich bag and observe.
- Throw away the zip lock bag.
Station 3: A Pointed Question
- Sharpen your pencil.
Stations 4, 5, and 6
Station 4: Precipitate Practice
- Place 3 eye droppers full of ammonia in the test tube. (DON’T MIX UP THE EYEDROPPERS!!!)
- Slowly, drop one drop of the copper sulfate at a time into the ammonia. (DON’T MIX UP THE EYEDROPPERS!)
- Watch the bottom of the test tube carefully. Do you see the white chunks forming? It’s a precipitate!
- Rinse out the test tube thoroughly.
The Reaction: Precipitate Formation
Station 5: Color Me Chemical!
- Carefully light the Bunsen burner.
- Take a wooden skewer and break it in half.
- Dip the frayed end of the skewer into the strontium chloride solution.
- Place the wet end of the skewer into the flame.
- Repeat steps 1-4 with the copper II sulfate solution.
Station 6: Blow It Up With Butane!
1. Close the zip lock bag so that there is only a small opening at the edge.
2. Place the tip of the butane bottle inside the opening.
3. Invert the bottle, and press the tip of the bottle on the table to release the butane inside the bag. Be careful! You don't need a lot!
4. QUICKLY seal the bag shut.
5. Observe the phase change that occurs. Keeping the bag sealed, touch the liquid with your fingers.
6. Throw away the zip lock bag.
Stations 7, 8, and 9
Station 7: What a Cut Up!
- Cut a circle out of the white sheet of paper.
- Fold the circle in half.
- Cut out different shapes along the fold to make a snowflake!
- If you would like, cut around the edges of the paper to make your snowflake look more real.
- THROW AWAY YOUR SCRAP PAPER!
Station 8: Blow it Up!
- Pour about an inch of vinegar into the flask.
- Use the funnel and fill the balloon with 2 scoops of baking soda. Use the skewer to get the baking soda through the funnel if you need to BUT be careful not to poke the balloon with the skewer.
- Stretch the open end of the balloon over the neck of the flask. Make sure it’s on tight!
- Hold onto the balloon at the flask, and pick up the heavy part of the balloon so that all of the baking soda falls into the vinegar at the bottom of the flask.
- Watch and be amazed!
- Rinse out the flask.
Station 9: Eeeeeew! Liver and Onions!
- Using tweezers, take a piece of the liver and place it in the sandwich bag. When you set down the tweezers, don’t let the handle touch the liver!
- Pour a about 20 mL (it doesn’t have to be exact) of hydrogen peroxide and pour it into the sandwich bag with the liver.
- Quickly close the bag! Touch and feel the baggie!
- Throw away the bag.
Stations 10, 11, and 12
Station 10: Bubblicious!
- Dip the stick into the bubble solution.
- Take a breath and exhale some air into the circle to blow a bubble.
Station 11: Dissolving or Color Change?
- Fill a beaker with 100 ml of water.
- Add one drop of food coloring to the water.
- Rinse out the beaker.
Station 12: Waxy Reaction
- Light a match.
- Place the flame on the wick of the candle to light the candle.
To close, as a class discuss whether each station is a chemical reaction, physical reaction, or both and share evidence that lead the students to that conclusion. This discussion is important! There are really insightful discussions that can occur and misconceptions that can be addressed as students hear the responses of their peers. For example, there will be many students who choose the "Blow it up with Butane" station as a chemical reaction, because there was a temperature change and gas production. However, through class discussion they can realize that the butane is simply evaporating and is therefore still butane and so it is a physical change.
Or, students may choose dissolving food coloring in water as a chemical reaction because there was color change. Again, students benefit from the discussion surrounding the idea that nothing new was produced and that the food coloring simply dissolved in the water. Even if during this class discussion a student offers the correct answer for these two stations, I follow up with a question such as, "Wait a second! When we added the food coloring, it changed color. Doesn't this mean it is a chemical change?" and "I thought that gas production and temperature change meant chemical reaction. How can this be a physical change?". Even if the student who shares their answer is correct, there are students in your class who are thinking the other way! Asking these questions can help clarify misconceptions for students who have the same question but don't want to ask in front of the class.
Another topic that is discussed is which stations are "chemical" or "both". For example, students can have great discussions about the candle station. Students only considering the fire might choose chemical; however, students looking closely enough to see the wax melting will note that it is "both".
In addition, a benefit of this discussion lies in the fact that there are twelve stations, which provides you with the opportunity to get lots of students involved in the whole group discussion!
The video below provides some insight into what to look for in your students' lab documents and some challenges that students have with some of the lab stations: