Investigating Changes of State: Chemical and Physical Changes
In this chemistry lab, students will observe a variety of changes in matter. They will observe cream changing into butter, frozen concentrated juice changing from a liquid and the chemical change of cooking pancakes. They will become engaged and explore changes in matter lab stations. They will explain Chemical and Physical changes using the Frayer Model and after reading Pancakes, Pancakes! categorize changes they heard take place in the book. They will elaborate with looking at a variety of menus and producing their own Chemical Change Cafe.
This activity is designed for students to investigate, make observations and describe chemical and physical changes. The student will observe that heating and agitation of matter can cause chemical change. Students will understand chemical and physical change is part of everyday life.
Context for Use
This activity will take at least 4 class periods. I will be teaching this activity to 2nd and 3rd graders. An electric frying pan will be needed along with pancake batter, cream to make into butter, jars, and the book Pancakes, Pancakes! by Eric Carle. For Changes in Matter lab you'll need: thumbtack, balloons, vinegar, baking soda, wax paper, spoon, pipette, fresh milk, sour milk, lump of clay, new steel wool, rusted steel wool, zipper baggies, 2 graduated cylinders, cream of tartar, thermometers labeled "1", "2", and "3", clear plastic cups. You will need to talk about safety issues with the cream in jars. What to do to prevent them from breaking and if they break what to do? Safety with a hot griddle in the room needs to be addressed with the students. Measuring to the nearest ¼ would be something they need to know how to do. This activity will take place during our Unit on Matter. It can easily be tied in with our language arts curriculum.
Resource Type: Activities:Lab Activity
Grade Level: Intermediate (3-5)
Description and Teaching Materials
Engage & Explore in lab stations; They move from station to station and decide if a physical or chemical change is occurring
Station 1 thumbtacks, balloons
Station 2 cup of vinegar, cup of baking soda, wax paper, spoon, and pipette
Station 3 cup of fresh milk covered with foil (labeled fresh), cup of sour milk covered with foil (labeled sour)
Station 4 Lump of clay
Station 5 new steel wool and rusted steel wool in water (leave in water for at least 24 hours)
Station 6 zipper baggies (1 per team), spoon, graduated cylinder, cup of cream of tartar, room temperature water, thermometers ( 3, labeled "1", "2", and "3".)
Station 7 graduated cylinder, clear plastic cups, cup of vinegar, and cup of milk
Changes that occurred in the stations were:
Physical changes: Station 1: Blowing up and popping a balloon; Station 4: Forming clay into different shapes
Chemical changes Station 2: Vinegar and baking soda reaction (gas bubbles produced); Station 3: Souring milk (change in odor); Station 5: Rusted steel wool (change in color); Station 6: Cream of tartar and water reaction (change in temperature); Station 7: Vinegar and milk reaction (precipitate formed)
Day 2: Explain differences between physical and chemical changes read from the article. Use Fryer model, Definition of chemical change, characteristics of chemical change, examples and non-examples of chemical change, Read Pancakes, Pancakes aloud. Read the book twice, once to enjoy and the next time to listen to examples of chemical and physical changes. Have them raise their hand when they hear an example. Have them tell you what kind of change it is and why. Physical changes: cutting wheat, separating grain from chaff, grinding wheat, squirting milk in the pail, churning butter (?), melting butter, chopping wood, breaking an egg, and stirring the batter. Chemical changes: burning wood for a fire, and cooking the pancake.
Day 3: Elaborate with making butter out of cream with the students. Give each student a clean baby food jar and fill it half full with whipping cream, place two clean marbles in the cream. Have students predict what they think will happen. Shake the jars. Have them notice any sound changes as the cream gets thicker. Caution them not to shake too hard or the jar may break.
As they're shaking their jars, look at a variety of restaurant menus and find examples of both physical and chemical changes. They will come up with ideas for their own "Chemical Change Only" menu the next day.
Day 4: Set up an electric griddle for adult use only to make pancakes. Place in groups and provide a box of just add water pancake mix, measuring cup, bowl and spoon or whisk and water and forks to eat the pancakes. On the menus the students will draw pictures of the batter before and after it is cooked and explain why cooking pancakes is a chemical change. Groups will come up to you with their prepared batter and observe changes as you cook the pancakes. "Watch as the batter is changed into a light and fluffy pancake. Add your homemade butter and a little syrup. Enjoy! I'm hoping to have parent volunteers to come in to help with this activity. Evaluate with new menu ideas for their "Chemical Change Cafe". You can give them this list and they can decide which ones go on their menu or they can brainstorm ideas with the class or on their own. Examples of new menus ideas would be: toast, scrambled eggs, buttermilk biscuits, cottage cheese, toasted marshmallows. Physical change items would be orange juice, strawberry smoothie, trail mix, orange-sickles, and fruit salad. You can list all these on a page and they can decide which ones would go on their menu. If they wanted to come up with any of their own they could as well.
Teaching Notes and Tips
The only concerns I have are with the pancake and butter making process. I think it could get a little hectic so I'm going to try and bring parents in to help with the pancake making and use the home-ec or cafeteria's kitchen.
When the students smell items at the lab stations, demonstrate for students the safe way to smell any chemical by "wafting".
Is turning cream into butter a chemical or physical change? This is a great discussion for students as I've found that all scientists don't agree. It's a great way to show that scientists don't even know everything.
4.11 A.1 heating of pancakes causes change in state of matter.
3.1 B.1 The student will ask questions to discover if a physical or chemical change has occurred.