Chemical+Change

Chemical Change P61

[|Baggie Chemistry]

[|Oxygen]

http://www.middleschoolchemistry.com/lessonplans/chapter6/lesson1 https://www.brainpop.com/science/matterandchemistry/chemicalequations/ Bozeman https://www.youtube.com/watch?v=X328AWaJXvI Crash Course kids https://www.youtube.com/watch?v=37pir0ej_SE Alcohol https://www.youtube.com/watch?v=CheFL8see30

Look at pages 16 & 17

https://www.nasa.gov/pdf/519347main_AP_ST_CO2Removal_Therm.pdf

Finding evidence of chemical change Burning candle- heat, soot Vinegar, baking soda, salt, sugar, etc



Lime Water precipitate - Calcium Hydroxide in water and carbonated water

Heat is often evidence of a chemical change. Pre-Show Lesson: Burning Money Post this question on the board: “How do we know if matter has undergone a chemical change?”

Materials: Per class: dollar bill, tongs, matches, salt, alcohol, water Per student: index card, copy of Digestive System Parts chart (Appendix A-1)

Procedure: 1. Instructional Focus Activity: you will need a dollar bill or higher denomination, tongs, matches or a lighter, salt, a solution of 50% alcohol and 50% water (you can mix 95% alcohol with water in a 1:1 ratio, if desired). Before the students enter, complete the following steps:


 * Prepare the alcohol and water solution. You can mix 50 ml of water with 50 ml of 95- 100% alcohol.
 * Add a pinch salt or other colorant to the alcohol/water solution, to help produce a visible flame.
 * Soak a dollar bill in the alcohol/water solution so that it is thoroughly wet.
 * Use tongs to pick up the bill. Allow any excess liquid to drain. Move the damp bill away from the alcohol-water solution.

When students arrive, tell them that you are going to light this one dollar bill on fire. Ask: “What changes would you expect to see and why?”

Light the bill on fire and allow it to burn until the flame goes out. Have students discuss possible explanations in small groups.

Scientific Concept Behind Burning Money: A combustion reaction occurs between alcohol and oxygen, producing heat and light (energy) and carbon dioxide and water. C2H5OH + 4 O2 -> 2 CO2 + 3 H2O + energy When the bill is soaked an alcohol-water solution, the alcohol has a high vapor pressure and is mainly on the outside of the material (a bill is more like fabric than paper, which is nice, if you've ever accidentally washed one). When the bill is lit, the alcohol is what actually burns. The temperature at which the alcohol burns is not high enough to evaporate the water, which has a high specific heat, so the bill remains wet and isn't able to catch fire on its own. After the alcohol has burned, the flame goes out, leaving a slightly damp dollar bill. http://chemistry.about.com/od/demonstrationsexperiments/ss/burnmoney_2.htm

Chemical Change – a change in color can be evidence of a chemical change. Activity Two: Disappearing Color Materials: small baby food jar, red food coloring, powdered bleach, teaspoon Procedure: 1. Fill the jar with water. 2. Add one drop of food coloring and stir. 3. Add and stir in one teaspoon of powdered bleach. 4. Observe after 15 minutes. Students should observe that the red color starts to fade and finally disappears. The water becomes clear except for any undissolved bleach. When the powdered bleach is added to the water it begins to slowly give off oxygen. The combination of this oxygen with the red dye causes the color to fade until it becomes colorless. .