In this hands-on lesson plan, students will observe chemical and physical changes, compare and contrast chemical and physical changes, and observe the signs of a chemical reaction.

Created by Laura Verastegui, December 2007

• Identify and demonstrate everyday examples of chemical phenomena such as rusting and tarnishing of metals and burning of wood.
  TEKS §112.23. Science (7)(A).
• Describe physical properties of elements and identify how they are used to position an element on the periodic table.
  TEKS §112.23. Science (7)(B).
• Recognize that compounds are composed of elements.
  TEKS §112.23. Science (7)(C).

Lecture:

1. Start the class by explaining the difference between a physical and chemical change (i.e., in a chemical change, new matter is produced).
2. Pass out LAB DATA SHEET: PHYSICAL AND CHEMICAL CHANGES.
3. Ask the students to give examples of physical changes, and write these examples on the board.
4. Review physical properties (mass, volume, malleability, heat and electric conductivity, color, density, state of matter).
5. Explain that physical properties describe physical changes.
6. Review chemical properties (flammability, reactivity, and oxidation).
7. Explain that chemical properties describe chemical changes.
8. Ask the students to give examples of chemical changes, and write these examples on the board.
9. Name different examples of change, and ask the students to classify them as chemical or physical changes.
10. Show the periodic table and explain why elements are in certain positions, briefly summarizing some physical and chemical properties of each group of periodic table.
11. Show different chemical reactions by example or by photos:
1. Alka-Seltzer in water
2. Burning gasoline
3. Leaves in autumn
4. Rusting of a metal
12. Ask the students what they observed in each chemical reaction.
13. Guide the students to identify the signs which give evidence for chemical reactions.
1. Gas formation (fizzing/bubbles)
2. Change in light or energy (hot, cold)
3. Change of color
4. Precipitate formation (solid)
14. Show some examples of chemical compounds and allow the students to identify the elements present in each example.
15. Explain that when writing elements, the first letter is always capitalized and, if the element’s symbol has two letters, the second one should be in lowercase. This will help the students better identify each element.

1. Label the test tubes with numbers 1-9.
2. Mix the following chemicals in separate test tubes
1. Baking soda and vinegar (gas formation)
2. Magnesium heated in a flame (light)
3. Iron sulphate and cooper (change of color and precipitate)
4. Potassium iodide and lead (II) nitrate (precipitate)
5. Zinc with Hydrochloric acid (gas formation)
6. Sodium hydroxide and Hydrochloric acid (gas formation and exergonic)
7. Heat some ice
8. Heat a small piece of lead until melt it
9. Dissolve water and salt
3. Test with the red and blue litmus paper the baking soda.
4. Test with the red and blue litmus paper the vinegar.
5. Test with the red and blue litmus paper the products of the reaction on test tube 1.
6. Test with the red and blue litmus paper the hydrochloric acid.
7. Test with the red and blue litmus paper the sodium hydroxide.
8. Test with the red & blue litmus paper the products of the reaction on test tube 6.
9. Write down all observations.

• Laboratory Data Sheet: Physical and Chemical Changes
• Extra Activity: Physical and Chemical Change
• Homework: Ask the student to write down a list of chemical reactions that they encounter in their everyday life during a week; ask them to describe observations and state the signs that support the evidence of chemical reaction.

Hydrochloric acid 1 M
Zinc
Baking soda
Acetic acid (vinegar)
Magnesium ribbon
Salt
Copper
Potassium iodide 1 M
Lead (II) nitrate 1 M
Distilled water
Test tubes
Sodium hydroxide 1 M
Ice
Lead
Hot plate
Bunsen burner
Blue Litmus paper
Red Litmus paper

See Laura Verastegui's class in action, at their Science Fair, 2008!

Vea esta lección en Español aquí