Before starting a new unit it is important to assess what your students already know about the topic. This will help to determine the level of your students’ understanding of chemistry, as well as identify misconceptions students might have internalized. I will begin my unit with a short brainstorming activity. Each student will be given a science journal to record observations, draw diagrams, and keep class notes. I will ask students to write the word chemistry on a clean sheet of journal paper. I will also do this on the blackboard. Students will be asked to tell what they think of when they hear the word “chemistry”. Record all words and phrases. Encourage student involvement. Ask questions, give clues, do not allow them to tell you they know nothing. Students will be asked to repeat this activity at the end of the unit to illustrate growth in content understanding as well as scientific vocabulary. Students will be required to copy the responses from the board onto their paper. This exercise should also promote reading and writing skills. Have students focus on the phonetic break down of the words. Validate all student responses, while emphasizing that chemistry is the study of everything they touch, taste, see or smell. Everything is made of chemicals, even invisible things such as air.
To further assess my students’ understandings of basic chemistry concepts, and to encourage scientific observation skills, I will set up the following demonstrations and ask my students to explain what they observe. All four demonstrations should be done in one class period to generate enthusiasm and curiosity for the topic they are about to study. Have another adult or student photograph each step of each demonstration. This will be used at a later date for students to display scientific explanations of each exercise.
1. The students will be shown a ball of clay and a ball of steel. Smash the ball of clay into a flat pancake shape. Attempt to do the same to the ball of steel. Ask the students to propose in writing and or diagrams why the clay ball could be flattened, but the steel ball could not. Ask them to imagine they could see the smallest parts of these balls through a very powerful microscope. What would they have observed ?
2. Place one tablespoon of salt into a beaker of water and stir. Place one tablespoon of cornstarch into a second beaker and stir. After stirring, the container with cornstarch is cloudy, and the container with salt is clear. Ask the students if they could see the smallest particles in each container, what do they think they would they be seeing? What is the difference between the containers?
3. Place an ice cube into a beaker and heat slowly on a hot plate until the ice melts and evaporates. Next, heat a piece of dry ice in the same manner. The dry ice will change to a “white cloud”. Ask the students to explain why dry ice behaves differently? Ask the students what they think happened inside each piece of ice during the heating process? And what do they think the “white cloud is made of?
4. Place a teaspoon of baking soda into a beaker. Add a small amount of vinegar. The students will see bubbles. Ask students if they had a powerful microscope that would allow them to see the smallest particle of each substance, what they think they would have seen before and after the vinegar was added?(2)
Depending on the severity of my students’ disabilities, I may want to put your students into groups for this exercise and allow the students to submit one explanation for the group. It would be preferable to have each student write or diagram his or her own response. If you have some higher level students who finish early, they can act as secretaries for students who have difficulty writing. This would enable each student to have his or her own response, which can be used as a self- assessment tool later in the unit. Each student will be able to measure growth against one’s own past performance, not the performance of his or her peers.
It is important for the teacher to read the student’s science journal and make encouraging comments on a regular basis. Students will quickly lose interest if they realize I do not have the time to keep up with their journal responses. Time should be given during class for journal responses. This must be seen as an important activity that warrants class time. Students should be allowed to collaborate and discuss ideas when writing. The teacher must circulate around the room to insure students are not merely copying each other’s work. This is also a time when the teacher can collaborate with individual students.
After students have finished writing and drawing in their journals, explain that scientists pondered these same questions for thousands of years before they decided what really happened to this matter. Scientists are men and woman who answer questions through observation, experimentation and data collection. Explain to your students that they have just taken the first step in becoming a scientist. Many great scientists have spent their entire life trying to answer similar questions.
After I have covered content information on the topics of density, dissolving, phase change, and chemical reactions, I will ask students to repeat the above exercise. I may repeat the above demonstrations or create a display of before and after photographs for the students to view before they write in their journal.
Student responses in demonstration 1 should include references to density, molecules being packed closer together, stronger bonds holding the atoms together, or the need for heat or chemicals to separate certain bonds. Remind students that substances can be strong without being dense. The atoms in clay are bonded in layers which allow the material to slide. Steel atoms are bonded in all directions.
Demonstration 2 should include responses such as “the salt molecules are separating in the water, and the starch seems to be thickening in the water, changing the appearance of the water. (I would leave this experiment out so students can see what material is left after the water evaporates. I would also encourage students to experiment with mixing both salt water and starch and water to different consistencies to observe each more closely.)
Demonstration 3 should include responses such as “The heated ice cube demonstrated all three phases of water. The dry ice skipped the liquid stage.” Then I would ask the students to try to come up with explanations for why it skipped the liquid stage. When students have devoted sufficient time to the question I will supply them with reference materials where they may search for the answer individually or as teams. The “white cloud” is actually water droplets. Similarly, when you see someone’s breathe on a cold winter’s day you are actually seeing water droplets in the air.
Demonstration 4 should include responses such as, two compounds came together in a chemical reaction and formed a new compound, or a gas was produced when baking soda reacted with vinegar.
Allow each team enough time to find the answer themselves. Do not become impatient and give the answer. Students who require more time will lose motivation to find answers on their own if they are not given the appropriate time they need. If I have a student with severe processing disabilities, I will sometimes give them the problem solving assignment before the other students. The rest of the class may be working on individual research projects. When we come together for our group problem solving, the student with processing disabilities will be able to keep up with the group. (This is an important life skill for students with disabilities. They must learn how to make requests for modifications when appropriate to insure success. Proficiency in a career does not always require speed over accuracy.) If given the choice to nurture thoughtful, time consuming, inquiry-based exploration, or finishing the content in the textbook, I will always choose the inquiry-based exploration, especially for the special education student.