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Mentos Gone Wild!
Lesson Overview
Learners become hooked on science when mentos candies are
dropped into soda and cause a huge eruption. Learners will
raise questions and design subsequent questions to test their
ideas.
Suggested Grade Levels: 3-
Standards for Lesson
Content Standard A: Science as Inquiry
Content Standard B: Physical Science
VA SOL:
3.1 a, c, j; 4.1 a, b, c; 5.1 g, h; 6.1 a, e, f, g, k; 6.5 a, b; LS.1 b, f, g, j; PS.1 g, h, n; PS.2 a, c, d; PS.5 a;
Time Needed
This lesson takes several class periods. Sample schedule:
Day One: Complete the Engage and Explore portion of the lesson
Day Two: Complete the Explain portion of lesson
Day Three: Complete the Elaborate and Evaluate portion of the lesson
Materials for Lesson
- Fresh raisins
- Clear plastic cup
- Clear, carbonated soda (for example, Club Soda, Sprite or 7-Up)
- 13 Mentos – mint
- 2 liter Diet Coke
Content Background
Information for teacher:
This experiment is fun and exciting and really hooks students (and adults) interest into the science behind it. What keeps up more intrigued is that scientists still don’t have a definitive answer. Experience chemists and physicists are still doing experiments to determine just what might be causing the eruption – is it chemical or physical change? Most would agree that it is physical.
Sodas contain sweeteners (sugar or artificial sweeteners), flavoring, water, and preservatives. Carbon dioxide (CO 2 ) gas is added to the soda through a high pressure process that causes the gas to dissolve into the liquid. The CO 2 gas remains suspended in the liquid and can not expand to form more bubbles due to the high pressure. When a soda is opened, a whoosh can be heard as the pressure is relieved and the dissolved gas escapes. When the pressure is decreased, the suspended carbon dioxide gas nucleates to build up more bubbles. If you shake the soda, the gas takes some of the soda with it as it escapes the container.
Water molecules like each other and stick together. This is called cohesion and is due to the polarity in water molecules - similar to magnetism. The positive hydrogen atom in one water molecule is attracted to the negative oxygen atom in the next molecule. This strong attraction causes surface tension at the surface of a liquid and adhesion at the surface of another object. In soda, the water molecules cling together around the carbon dioxide (CO 2 ) gas bubbles. Bubbles can’t expand or form new bubbles unless this strong attraction between water molecules is weakened and the tension is broken.
When the Mentos are dropped into the soda, the gum arabic in the coating of the Mentos weakens the attraction of the water molecules around the CO 2 gas bubbles. As soon as the Mentos hit the soda, the carbon dioxide nucleates, or forms more bubbles, in the tiny, porous pits that are all over the Mentos surface. Couple this with the speed at which the Mentos are sinking to the bottom of the bottle and an eruptive blast occurs as the CO 2 is released and breaks free taking much of the liquid with it.
Engage
Pour a glass of clear soda for each group of students and have student make observations. They should notice the bubbles that collect on the sides of the glass and come up from the bottom of the glass. Give students 5-6 raisins per team and have them make observations using a hand lens. Students should record observations, make drawings, and list some physical properties about both soda and raisins in their science notebook.
Elaborate
Design an experiment to test how different variables affect the eruption of soda. Teachers will guide students to design their own experiment to test what affects the eruption. This experiment can be completed by the entire class or in small groups.
THINK-PAIR-SHARE: Using the 4-question design sheet, have students THINK about question one and record responses. After one minute, have students pair with their shoulder partner and RALLY ROBIN to compare and add answers. Then allow students share answers with the class. Some ideas that students might generate based on changing the materials include:
- Different brands or types of soda
- Diet vs. regular
- Diet soda with aspartame or Splenda
- Amount of soda
- Caffeine or Decaf
- Size of bottle
- Type of mentos – mint (matte finish) or fruit-flavored (glaze finish)
- Whole mentos vs. crushed mentos (more surface area)
- Number of mentos
- New mentos vs. used mentos
- Sand off mentos coating – Will the “naked” mentos have the same effect? If the sanded coating is dropped into the bottle, will it still cause an eruption?
Evaluate
Experimental Design Student Participation – Follow safety rules
What do you see with your eyes?
What do you smell with your nose?
What do you hear with your ears?
Observation Sheet
3. Safety Sheet
The following safety rules are to apply to this
activity:
- Roll up long sleeves and tie back long
hair.
- Wear safety goggles over your eyes.
- When you adding Mentos to soda, point
the open end away from yourself and
others. Back away quickly.
- Keep your work area clean and clear of
materials.
- Do not eat the Mentos or drink the soda!
Safety Check-Off Sheet
Before you begin, check here to make sure
you are ready for the activity:
Are your sleeves rolled up?
Long hair tied back?
Do you have your goggles on?
Did you point the open end of the bottle
away from youself and others when you
added Mentos to soda?
Did you back away quickly?
Is your work area clean and clear of
materials?
