syensaya 2011 chemistry demonstrations

SyenSaya 2011 Demonstrations CHEMISTRY

Ma. Desiree A. Belina-Aldemita, M.Sc.

Coordinator for Extension

Institute of Chemistry, CAS, UPLB

1

Demo 1 THE 'MAGIC BLUE BOTTLE'

DESCRIPTION

This demonstration can be used with younger children (e.g. grades 3-5 or so) to simply

show the dissolution of gases into liquids. Generally they are more familiar with solids (e.g. sugar or salt) dissolving in water – this demonstrates that gases can be dissolved in liquids, just like solids can. This experiment is also a visually dramatic way to teach

reduction-oxidation (redox) chemistry.

MATERIALS

REAGENTS

methylene blue glucose NaOH

distilled water

GLASSWARES/APPARATUS

bottle/ test tube stopper

PROCEDURE

1. Place water in a clear bottle, up to ¾ full. Add one tbsp glucose and stir.

2. Add NaOH to the solution, dissolve completely.

3. Add 1-2 drops of methylene blue.

4. Shake the bottle with the blue solution vigorously.

5. Observe the color change after 20 seconds.

6. After noting the change in color, shake it again and note again the color of the

solution inside.

THEORY

The solution in the bottle has glucose, lye (NaOH), and methylene blue (an organic dye).

Glucose is a reducing agent and in alkaline solution will reduce methylene blue to a colorless form. Shaking the solution admits oxygen which will reoxidize the methylene blue

back to the blue form. The color change is an indication of the reduction-oxidation reaction (Redox) taking place in solution. Common (biological, environmental) oxidation reactions involve oxygen (air) as an important reagent.





2

Demo 2 COLOR CHANGING MILK

DESCRIPTION

Some very unusual things happen when milk, food coloring and soap are mixed. This

experiment is used to uncover the scientific secrets of soaps.

MATERIALS

REAGENTS

milk

food coloring (yellow, green, red, blue) dishwashing soap

GLASSWARES/APPARATUS plate

cotton buds

PROCEDURE

1. Pour enough milk in the dinner plate to completely cover the bottom. Allow the milk to settle.

2. Add one drop of each of the four colors of food coloring - red, yellow, blue, and

green - to the milk. Keep the drops close together in the center of the plate of milk. 3. Place a drop of liquid dish soap on the one end of the cotton swab. Place the soapy

end of the cotton swab back in the middle of the milk and hold it there for 10 to 15 seconds.

THEORY Milk is a solution that is made up of water, vitamins, minerals, proteins, and droplets of

fat. Fats and proteins are sensitive to changes in the surrounding solution (the milk). When soap is added, the weak chemical bonds that hold together the proteins and fat in the

milk solution are changed. The molecules of protein and fat bend, roll, twist, and contort in all directions. The food color molecules are bumped and shoved everywhere, providing an

easy way to observe all the invisible activity. At the same time, soap molecules combine to form groups of soap molecules. The soap molecule groups mix with the fat in the milk

causing the milk fat and dish soap to swirl and churn. Once the soap molecule groups and milk fat are evenly distributed throughout the milk, the motion stops.





3

Demo 3

CHEERS! TURN WATER INTO WINE, MILK AND BEER

DESCRIPTION

This demonstration shows the concepts on acid-base reactions, indicators and precipitation reactions. A glass filled with what looks like water is poured into a second glass, where it

"magically" turns into wine. When the wine is poured into a third glass, it changes to milk, and when the milk is poured into a fourth glass, it changes to beer!

MATERIALS REAGENTS

water sodium bicarbonate

sodium carbonate phenolphthalein indicator

barium chloride sodium dichromate

hydrochloric acid


tumblers wine glass

beer mug

PROCEDURE

1. Begin with a tumbler containing "water". 2. Pour the "water" into a wine glass.

3. Pour the "wine" into a second tumbler. 4. Pour the "milk" into a beer mug.

THEORY

Sodium carbonate is a basic solution that looks like water. Adding phenolphthalein will

make the solution purple, and look like wine. Adding barium ions will precipitate out a suspension of Ba(OH)2, which will look like an opaque white liquid (milk!). In the last glass,

the concentrated acid will (a) acidify the remaining base, eliminating the Ba(OH)2 (b) result in the evolution of CO2 gas and (c) make a beer-like color with the indicator.





4

Demo 4 BOUNCING POLYMER BALLS

DESCRIPTION

Polymers, which are large molecules composed of repeating chemical units, are used to

make numerous things, including clothing, non-stick cookware, bulletproof vests, plastic containers, and toys. In this activity, students will be able to make colorful bouncing balls from the readily available polymer samples, glue and cornstarch plus borax. This activity

demonstrates an interesting chemical reaction, primarily between the borax and the glue.

MATERIALS

REAGENTS

borax white glue corn starch

water


beaker spoon graduated cylinder

meter stick

PROCEDURE

A. Ball # 1

1. In a glass beaker, mix 3 level spoonfuls of glue and 5 mL water. Then add 1 level

spoonful of borax.

2. DO NOT STIR. Allow the ingredients to interact on their own for 10-15 seconds and then stir them together to fully mix. Once the mixture becomes impossible to

stir, take it out of the beaker and start molding the ball with your hands. 3. The ball will start out sticky and messy, but will solidify as you knead it.

B. Ball # 2

1. Mix 3 level spoonfuls of glue, 5 mL water, and 1 level spoonful of cornstarch.

Then add 1 level spoonful of borax.

2-3. Same as ball #1

C. Ball # 3

1. Mix 3 level spoonfuls of glue and 1 level spoonful of cornstarch. Then add 1 level

spoonful of borax.

2-3. Same as ball #1

http://www.hometrainingtools.com/polymer-slime-experiments/a/1229/





5

THEORY

The white glue contains polyvinyl acetate, a strong and flexible polymer that gives the ball strength. The borax acts as a “cross-linker” to the polymer molecules in the glue – basically it creates chains of molecules that stay together when you pick them up. The

cornstarch helps to bind the molecules together so that they hold their shape better. Cornstarch contains amylopectin, a polymer whose shape is best described as "branched"

- it sticks out like the branches of a tree - and gives the ball the property of elasticity. Elasticity allows the ball to return to its original shape after being compressed or

stretched, such as hitting the floor. So instead of splattering everywhere, the ball bounces back up. The borax is needed to help the glue and the starch stick together. This connects

the two polymers into a netlike formation, keeping the ball from crumbling or becoming slime when it is bounced.





6

Demo 5 REUSABLE HEAT PACK: CRYSTALLIZATION FROM

SUPERSATURATED SOLUTIONS OF SODIUM ACETATE

DESCRIPTION

This demonstration illustrates three concepts: the process of crystal growth from a solution, the properties of saturated solutions and the idea that a seed crystal must be made of the same substance as the crystals that will grow. A supersaturated solution of sodium acetate

is crystallized by pouring it onto a seed crystal, forming a stalagmite-like solid. Heat is radiated from the solid. A commercial application of this crystallization process will be

shown. A metal disc is manipulated inside a sealed plastic bag holding the sodium acetate solution. This causes the sodium acetate to crystallize. This heating pack provides an easily

portable method of having heat available whenever and wherever it is needed.

MATERIALS

REAGENTS sodium acetate

water commercially available reusable heat

pack

GLASSWARES/APPARATUS test tube

stove heating pot

THEORY

Sodium acetate trihydrate is unusual in the stability of its supersaturated solutions. Most such solutions will spontaneously crystallize from the slightest mechanical disturbance. Without a seed crystal to act as a template for formation of a crystal lattice, crystallization is very slow and a solution can be supersaturated for a long time. Because

this crystallization process is exothermic it has practical application as a heating pad. The Reusable Heat Pack contains sodium acetate, a form of salt, which under normal conditions

in an open container will change from a liquid to a solid (freeze) at 130ºF (54ºC). By placing this solution in a sealed container, the solution can be cooled well below this temperature (as low as 14ºF) (-10ºC). Flexing the patented stainless steel "trigger" within

the sealed container causes a single molecule of liquid to crystallize which starts a chain reaction causing the entire solution to change from a liquid to a solid. This phase change

causes the pack to heat to approximately 130ºF.

syensaya 2011 chemistry demonstrations

Documents