Self-made indicator

Experimental principle

Many plants contain pigments in their flowers, fruits, stems and leaves. These pigments show different colors in acidic or alkaline solutions and can be used as acid-base indicators.

experimental supplies

test tube, measuring cylinder, glass rod, mortar, rubber-tipped dropper, drip plate, funnel, gauze.

Petals (such as morning glory), plant leaves (such as purple cabbage), radishes (such as carrots and Beijing heart radish), alcohol solution (the volume ratio of ethanol to water is 1: 1), dilute hydrochloric acid and dilute NaOH solution.

experimental steps

1. Take some petals, plant leaves, radishes, etc. and mash them in a mortar, then add 5 mL of alcohol solution and stir. Filter with four layers of gauze respectively, and the obtained filtrates are alcohol solutions of petal pigment, plant leaf pigment and radish pigment respectively, which are packed in three test tubes.

2. Drop some dilute hydrochloric acid, dilute NaOH solution and distilled water into the holes of the white drip plate, and then drop 3 drops of petal pigment alcohol solution respectively. Observe the phenomenon.

3. Use the alcohol solution of plant leaf pigment and radish pigment instead of the alcohol solution of petal pigment to do the above experiment and observe the phenomenon.

Making white sugar from brown sugar

Experimental principle

Brown sugar contains some colored substances. To make white sugar, it is necessary to dissolve brown sugar in water, add appropriate amount of activated carbon, adsorb the colored substances in brown sugar, and then filter, concentrate and cool to get white sugar.

experimental steps and phenomena

weigh 5 g ~ 1 g of brown sugar in a small beaker, add 4 mL of water, heat to dissolve it, add .5 g ~ 1 g of activated carbon, stir constantly, and filter the suspension while it is hot to obtain a colorless liquid. If the filtrate is yellow, add an appropriate amount of activated carbon until it is colorless. Transfer the filtrate to a small beaker and evaporate and concentrate in a water bath. When the volume is reduced to about 1/4 of the original solution, stop heating. Take the beaker out of the water bath and cool it naturally, and white sugar will precipitate.

determination of vitamin c in vegetables

experimental principle

starch solution will turn blue-purple when it meets iodine, which is the characteristic of starch. Vitamin C can react with iodine in the blue-purple solution, making the solution colorless. Through this principle, it can be used to test vitamin C in some vegetables.

experimental steps and phenomena

put a small amount of starch in a glass bottle, pour some boiling water, and stir with a small stick to form a starch solution. Drop 2 ~ 3 drops of iodine, and you will find that the milky white starch liquid turns blue-purple. Find 2 ~ 3 pieces of green vegetables, remove the leaves, leave the petiole, squeeze out the juice from the petiole, and then slowly drip the juice into the blue-purple liquid in the glass bottle, stirring while dripping. At this time, you will find that the blue-purple liquid has become milky white again. Explain that vegetables contain vitamin C.

homemade soft drinks

soft drinks are made of mineral water or drinking water that has been boiled and disinfected by ultraviolet radiation, and filled with carbon dioxide. Belonging to carbonated drinks containing carbon dioxide. The factory makes soda by pressurizing to dissolve carbon dioxide gas 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 dissolved with 1 volume to 4.5 volumes of carbon dioxide. In addition to carbon dioxide, some soft drinks also contain appropriate amount of sugar, fruit juice and essence.

When carbon dioxide is discharged from the body, it can take away some heat, so drinking soda can relieve fever and quench thirst. When drinking iced soda, because the temperature of soda is lower, more carbon dioxide is dissolved (at ℃, the solubility of carbon dioxide is twice as large as that at 2℃), and more carbon dioxide is discharged from the body, which can take away more heat, so it can lower the temperature of the stomach. Therefore, you must not drink a lot of iced soda, so as not to have a strong cold stimulus to the stomach, cause stomach cramps, abdominal pain, and even induce gastroenteritis. In addition, excessive soda will dilute gastric juice, reduce its digestive ability and bactericidal effect, affect appetite, and even increase the burden on the heart and kidneys, causing physical discomfort.

you can also make your own soda in the laboratory and at home. Take a washed soda bottle, add 8% cold boiled water to the bottle, then add sugar and a small amount of fruity essence, then add 2 g sodium bicarbonate, stir and dissolve, and then quickly add 2 g citric acid. Immediately press the bottle cap tightly, so that the generated gas can not escape, but dissolve in water. Put the bottle in the refrigerator to cool down. After taking it out, open the bottle cap and you can drink it.