Experimental principle
Cobalt hydroxide will show different colors when it loses water gradually when heated, so it can change according to the temperature.
The change of color is made into a thermometer.
Experimental steps and phenomena
Add half a test tube filled with 95% ethanol and a little red cobalt chloride crystal (CoCl2? 6H2O)，
Dissolved by oscillation, it is purple-red at room temperature, and its color is blue-purple to pure blue with the increase of temperature when heated.
2. soda-acid fire extinguisher
Experimental steps and phenomena
(a) As shown in the figure below, use a large bottle with a single-hole rubber stopper and insert the glass tube. Put it in a bottle
Add some sodium bicarbonate solution, take a test tube that can be put into a bottle and fill it with concentrated hydrochloric acid. Take your time.
Put it in a bottle to make the test tube stand upright, and put a rubber stopper with a glass tube on it. Please turn the bottle upside down when using the fire extinguisher.
Aim the glass nozzle at the flame. Watch out! Don't point the nozzle at others or yourself.
(b) adding a detergent to the acid to produce a covering foam. Aim the bottle at the flame, quickly.
When the bottle is turned upside down, the violent reaction produces a lot of carbon dioxide, and then the pressure of the gas will press the liquid out of the nozzle and destroy it.
It's on fire.
3, wand lighting
Can a glass rod be used instead of a match to light an alcohol lamp?
Experiment: put a small amount of potassium permanganate crystal on the mirror (or glass), drop 2 or 3 drops of concentrated sulfuric acid on potassium permanganate, dip it with a glass rod, and touch the wick of the alcohol lamp, and the alcohol lamp will light up immediately.
4. Build an "underwater garden"
Sodium silicate (Na2SiO3) was dissolved in water to make water glass with 40% solute mass fraction, and then it was gently mixed with sodium silicate.
Crystal grains of salts, such as chlorides of cobalt, iron, copper, nickel and lead, sulfates of aluminum, iron, copper and nickel, cobalt,
Nitrates of iron, copper and nickel, added to water glass (be careful not to shake), are colorful "flowers".
It grew up slowly.
Step 5 paint
Experimental principle
FeCl3 _ 3 _ 3 solution is blood red in the presence of potassium thiocyanate (KSCN), blue in the presence of potassium ferrocyanide [K4 [Fe (CN) 6]], green in the presence of potassium ferricyanide [K3 [Fe (CN) 6]] and purple in the presence of phenol. FeCl3 _ 3 solution is yellow when sprayed on white paper.
Experimental supplies
White paper, brush, sprayer, wooden frame, nail clippers.
Ferric chloride solution, potassium thiocyanate solution, concentrated potassium ferrocyanide solution, concentrated potassium ferrocyanide solution, concentrated phenol solution.
experimental procedure
1. Dip potassium thiocyanate solution and concentrated potassium ferrocyanide solution,
Concentrated solution of potassium ferricyanide and concentrated solution of phenol are coated on white paper.
2. Dry the paper and nail it on the wooden frame.
3. Spray FeCl _ 3 solution on white paper with pictures with a sprayer.
6, wood carving or bamboo carving (word) method
Reaction principle: dilute sulfuric acid is heated into concentrated sulfuric acid, which has a strong dehydration effect and makes cellulose
(C6H 10O5)n loses water and carbonizes, so it appears black or brown. Wash off excess sulfuric acid and put it on a wood (bamboo) machine.
Get black or brown flowers or words.
Experimental steps: Draw flowers or write on wood (or bamboo) with a brush dipped in 5% dilute sulfuric acid.
Words. After drying, put the wooden (bamboo) container on a small fire for a period of time, wash it with clear water and put it on the wooden (bamboo) container.
Get a black or brown pattern or handwriting.
7. Traces of protein
Take an egg, wash the oil on the surface and dry it. Dip the brush in acetic acid and write on the eggshell. After the acetic acid volatilizes, cook the egg with dilute copper sulfate solution, and peel off the eggshell after the egg cools, leaving clear blue or purple handwriting on the egg white, but leaving no trace on the eggshell.
This is because acetic acid can dissolve a small amount of protein after dissolving eggshells. Egg white is a globulin composed of amino acids, which hydrolyzes under weak acidic conditions to produce peptides and other substances, and the peptide bonds in these substances are complexed with Cu2+ and appear blue or purple.
8. Violet discoloration experiment
-Principle of acid-base indicator
Violets are in full bloom this season. You can use violets as acid-base indicators.
See the new textbook (People's Education Edition) for the experimental operation, which is very interesting. This experiment is simple and clear. It also goes well with chrysanthemums.
Boyle first proposed the concept of acid-base indicator by accident.
9. Check the iodine in iodized salt.
Experimental principle
Iodized salt contains potassium iodate (KIO3), but generally does not contain other oxidizing substances. Under acidic conditions, IO3- can oxidize I- to I2, and it will turn blue when it meets starch test solution. However, salt without iodine cannot have a similar reaction.
Experimental supplies
Test tube, rubber head dropper.
Iodized salt solution, non-iodized salt solution, KI solution, dilute sulfuric acid, starch test solution.
experimental procedure
1. Add a small amount of iodized salt solution and non-iodized salt solution into two test tubes, and then drop a few drops of dilute sulfuric acid and a few drops of starch test solution respectively. Observe the phenomenon.
2. Add an appropriate amount of KI solution and a few drops of dilute sulfuric acid to another test tube, and then add a few drops of starch test solution. Observe the phenomenon.
3. Pour the liquid in the third test tube into the first two test tubes respectively, mix them evenly and observe the phenomenon.
10, homemade soda
Soda is made of mineral water or drinking water after boiling and ultraviolet irradiation disinfection, and filled with carbon dioxide.
Yes Belonging to carbonated drinks containing carbon dioxide. This factory makes soda by pressurizing carbon dioxide.
Soluble in water. The more carbon dioxide dissolved in soda, the better the quality. The soda sold in the market is about
1 volume of water is dissolved in 4.5 volume of carbon dioxide with 1 volume of carbon dioxide. Besides carbon dioxide, some soft drinks also contain suitable chemicals.
Measure sugar, juice and essence.
When carbon dioxide is excreted, it can take away some calories, so drinking soda can reduce fever and quench thirst. Drink iced drinks
When soda is used, more carbon dioxide is dissolved due to the lower temperature of soda (the solubility of carbon dioxide at 0℃
Compared with 20℃ 1 times), there is more carbon dioxide to be excreted, which can take away more heat, so there is more.
Can lower the temperature of the stomach. Therefore, don't drink a lot of ice soda, so as not to have a strong cold on your stomach.
Stimulation, causing stomach cramps, abdominal pain, and even inducing gastroenteritis. In addition, excessive soda will dilute gastric juice and reduce it.
The digestive ability and bactericidal effect of gastric juice affect appetite, even increase the burden on the heart and kidneys, causing physical discomfort.
Soda can also be made in the laboratory and at home. Take a washed soda bottle and fill it with volume.
Accumulate 80% cold boiled water, then add sugar and a small amount of fruity essence, and then add 2 g sodium bicarbonate to stir and dissolve.
After that, 2 g of citric acid was quickly added. Press the bottle cap tightly immediately, so that the generated gas can not escape, but dissolve in it.
Put the bottle in the refrigerator to cool. After taking it out, open the bottle cap and you can drink it.