# Choositz Decision Balls

SKU #SS-35
(5 reviews)
Availability: In Stock
Qty.
One ball bounces high while the other hits the floor and stops immediately.

Description

These "Happy-Sad" balls are 1.0" in diameter. The two black rubber balls appear to be identical, but have extremely different physical properties. Dropped onto a hard surface, one ball bounces while the other hits the surface and barely bounces at all. Show students that some properties cannot be observed without experimentation. Set includes two balls (one "yes" and one "no").

Video

Lesson Ideas

Demonstration:

Two balls which look identical are dropped from the same height onto a hard surface. One bounces to almost the same height, while the other does not bounce at all.

Explanation:

Although the two balls have some similar physical properties, such as size, color, and density, they differ greatly in elasticity. The one which bounces demonstrates an almost perfect elastic collision with a hard surface. Very little of its kinetic energy is converted into heat in the collision. This ball is often referred to as a 'super ball'. The ball which does not bounce demonstrates an almost perfect inelastic collision. Most of the kinetic energy is converted into heat.

The ball which bounces is made from polyneoprene, which has large chlorine groups to restrict rotation on every fourth carbon in the long chain. Numerous cross links between polymer chains restrict the slipping of one chain past another. With little bond rotation and chain slippage, the energy of the fall cannot easily be converted into heat. To conserve the energy of the fall, the molecules move and then quickly return to their original position. At room temperature, consequently, the ball deforms on impact and then immediately returns to a spherical shape, cause the ball to bounce back to almost the same height as dropped. This phenomena is very temperature dependent. If cooled to about -40o C, these collisions become inelastic and the ball will not bounce well.

The ball which does not bounce well is make from polynorbornene, which has a 5-membered ring as part of the chain structure. Although this group restricts the movement, the molecule absorbs most of the energy of a fall. With more degrees of molecular freedom, this polymer does not quickly return to its original shape. Thus, at room temperature, the energy of the fall is absorbed within the molecules in the form of heat. Even cooling this ball in the freezer changes its elastic properties so that a small bounce can be observed.

Reviews

5 reviews
Aug 8, 2023
Buy two sets--one set to demonstrate the differing properties of the two balls, and another set to demonstrate the concepts of impulse and force. Attach a small "I-bolt" to each ball in one set and hang them by thin strings to a horizontal rod. Set identical books or bricks on end to the two balls hand at the same height and barely touch the books/bricks. Release each ball from horizontal and allow it to fall and hit the book/brick. (This assures that the balls have the same momentum (mv) when they hit the books, since the balls have the same mass and will have the same kinetic energy when they hit, so they'll have the same momentum). The "happy" ball, which is more bouncy, will knock the book/brick over, but the "sad" ball will not. Why? The sad ball's change in momentum (or impulse), goes from mv to zero, its impulse and force on the book/brick is less. The happy ball's change in momentum goes from mv to negative mv, so the change in momentum is greater, so the impulse and force are greater.
Connie Wells

0   0

Choositz Decision Balls
Apr 10, 2019
These balls truly demonstrate a variety of chemical concepts that can be discussed with audiences ranging from kids to adults. I've used them both at outreach events as well as classes here at Duke, including organic chemistry. Merely a change in the material (chemical structure) changes the properties of the material they are composed of, including their ability to transfer or retain energy. This demonstration goes along nicely with another demonstration I have (which I understand is no longer available) involving pure aluminum and an amorphous alloy. Two steel balls of equal size are dropped on each metal surface showing that the energy transfer to the aluminum is greater than to the amorphous metal. Combined, the two demonstrations show that the composition of the balls and of the surface they bounce from affect the energy transfer. I do not know if E. I. can find this demonstration to sell, put if they can it would be a great addition to their wonderful list of products.
Kenneth Lyle

1   0

Best Happy/Sad Balls I have found!
Feb 11, 2019
I am very impressed by the size and cost of the happy/sad (or choositz) balls. I wish they were a little closer in mass, because you can tell which is which without bouncing. I bought two sets, and I normally will use 3 (2 happy and 1 sad) when demonstrating these (specifically for polymer properties) - Normally I give the teacher/parent/adult the sad ball and the kids/students the happy ball. You can then mess with the adults a little, saying they forgot how to bounce a ball. Perfect for starting a conversation about STEM.
Jeromy Rech

0   0

Fantastic product and service
Jan 7, 2015
Ordered 8 sets Choositz decision balls (happy/sad balls)during the holiday season, a time where items can be out of stock and weather can delay your delivery. Educational Innovations Inc. had what I needed, and were able to deliver to Hawaii way ahead of time for my trainings without having to pay any extra cost for the shipping. Thank you for a wonderful product and service!
Kazz Kalama
Owner Response: Thank you, Kazz!

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HS Science Instructor
May 22, 2012
My students love the "Happy-Sad"lab. They are facinated by ball that won't bounce. I bought them to use for the energy unit in physical science, but now use them for other classes/topics as well.
F. Scott

0   0

### NGSS

This product will support your students' understanding of the Next Generation Science Standards (NGSS)*, as shown in the table below.

 Elementary Middle School High School 4-PS3-1 Students can use the Choositz Decision Balls as evidence to construct an explanation relating the speed of an object to the energy of that object. 4-PS3-2 4-PS3-3 4-PS3-4 Students can use Choositz Decision Balls to apply scientific ideas to design, test, and refine a device that convert energy from one form to another. MMS-PS3-1 MS-PS3-3 Students can use the Choositz Decision Balls to apply scientific principles to design, construct, and test a device that either minimizes or maximizes thermal energy. MS-PS3-4 Students can use Choositz Decision Balls to plan an investigation to determine that the relationships among the energy transferred, the type of matter, the mass, and the change in the average kinetic energy of the particles as measured by the temperature of the sample. HS-PS3-3 Students can use Choositz Decision Balls to design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy.

Suggested Science Idea(s)

4-PS3-1
4-PS3-2
4-PS3-3
4-PS3-4
MS-PS3-1
MS-PS3-3
MS-PS3-4
HS-PS3-3

Students can use the Choositz Decision Balls in a number of different investigations of kinetic and thermal energy. Although the balls have shared physical properties, due to the unique elasticity of any two balls, students can explore energy transfer in a new manner.

* NGSS is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of, and do not endorse, this product.

Q & A