TEKS & Objectives
7.6. Matter and energy. The student knows that matter has physical and chemical properties and can undergo physical and chemical changes. The student is expected to distinguish between physical and chemical changes in matter.
7.1.A demonstrate safe practices during laboratory and field investigations as outlined in Texas Education Agency-approved safety standards
We will observe phases of matter.
I will identify and compare chemical and physical changes.
1. Review vocabulary and complete quiz.
States of matter The main forms matter can exist in: Solid, Liquid and Gas
Physical change A type of change in which a new substance is NOT formed. For example: water boiling or cut paper.
Chemical change A type of change in which a new substance is formed. For example: burning something.
Catalyst A substance that speeds up a chemical reaction
2. It’s surprise history time!
3. Make invisible ink two ways.
Watch the video below to see how to use a chemical change to create invisible ink.
Invisible ink recipe ingredients:
- 1/2 teaspoon baking soda
- 3 tablespoons water
- 1/8 teaspoon turmeric
- 1 tablespoon 70% Isopropyl Alcohol (rubbing alcohol found in the drugstore)
Invisible ink recipe steps:
- Mix the baking soda and water together. This is your invisible ink.
- Use a cotton swab or paint brush to write or draw your secret message onto your white sheet of paper. Let it dry.
- In a separate cup, mix the turmeric and alcohol together.
- Use a paintbrush to paint over your secret message with the turmeric/alcohol mixture.
- Reveal your secret message!
Write a secret message between the lines of this letter, just like Revolutionary spies wrote to General George Washington!
You can also use a physical change to create invisible ink.
The waxy crayon creates a physical barrier preventing the watercolor paint from touching the paper where your secret message is.
Bonus method using a physical change to create secret messages:
- Write a message on a pad of paper, pressing your pen or pencil fairly hard onto the paper so that it dents a little.
- Tear the top page with the message off of the pad of paper.
- Take a pencil and hold it at an angle like you are shading a drawing.
- Lightly rub the graphite tip of the pencil on its angled side.
- As the paper becomes shaded by the pencil, the secret message will remain white.
- This happens because the paper has been dented downward and the message is not getting rubbed by the pencil.
- This is a physical change to the paper because no new substance has been made.
Speaking of spies…
What do you call an underwater spy?
James Pond
4.“Is it a physical or chemical change?”
