Experiments with water

Everyone knows that water is a chemical compound, and its chemical formula - H2O - is well known to everyone. Water consists of two elements - hydrogen and oxygen. Let's experiment with it, namely, try to decompose the water into its constituent parts and then create it again. This is not an easy task because water is a very stable compound. In order to separate a hydrogen atom from an oxygen atom, very strong auxiliary means are needed, and on the contrary, hydrogen and oxygen combine easily and extremely violently. In addition, well-known safety rules for working with chemicals should be followed.

Everyone knows that water is a chemical compound, and its chemical formula - H2O - is well known to everyone

Pour iron powder into a test tube of refractory glass with a layer of 2-3 cm. Then add dropwise 0,5 ml of water. Iron powder absorbs water. Add another approximately three-centimeter layer of dry iron powder to the wet mixture. We close the tube with a rubber stopper, through which we pass a curved glass tube with an internal section of 3-6 mm. We protect the inner side of the cork from strong heat with a piece of sheet asbestos, asbestos or glass wool. Then, we attach the tube at an angle to a tripod or to the tube holder at an angle (Fig. 1). The vent pipe will be immersed in water and above its end we will strengthen the inverted tube filled with water.

For the success of the experiment, it is necessary that the iron powder, starting from the dry end of the column, be heated as much as possible. To do this, you need a strong Bunsen burner. If the gas pressure is not too low, we will increase the air supply as much as possible so that the flame is divided into an inner cone and a “non-luminous” external part. However, one should not allow the flame to slip (a weak whistle indicates it), since in this case combustion starts already inside the burner and it heats up very much.

We install the burner under the test tube so that the hottest outer edge of the non-luminous flame flows around the test tube. First, we will heat the area located slightly above the dry column of iron powder until the tube is noticeably heated. Then slowly bring the flame under the zone of dry iron powder.

The wet layer heats up, water evaporates, and water vapor interacts with hot iron powder. In this case, iron captures the oxygen of water, and hydrogen is released. It passes through a glass tube, and bubbles form in the trap, which collect in a test tube filled with water. This happens so quickly that we will have time to fill the second tube.

If gas bubbles cease to form, stop heating and set fire to the hydrogen that has formed. To do this, turn the tube upside down, open and insert the flame from below into the hole. The gas will burn quickly. We will see the blue flame and hear the whistling sound, and maybe a strong clap. Just in case, so as not to get injured by fragments in a possible explosion, before setting fire to the gas, wrap the tube with a damp cloth.

Iron easily combines with oxygen, so it can displace hydrogen from water. At room temperature, this process proceeds very slowly, on the contrary, at a temperature of red heat - rapidly. Hydrogen burns when ignited. In this case, it combines with the oxygen of the air, and again water forms. If hydrogen is not mixed with oxygen or air from the very beginning, combustion proceeds quietly. A mixture of hydrogen with air or pure oxygen explodes. This mixture is called explosive gas.

Based on our first experience, we can give a general recipe for the decomposition of a chemical compound: in order to release component A from compound AB, you need to react with it substance C, which combines with B more easily than A. Iron is more prone to form a compound with oxygen, than hydrogen, and as a result displaces it from water. Other metals are also capable of this, for example zinc, aluminum, magnesium or sodium. Such metals are called active, while inactive metals: copper, silver, gold and platinum - can not decompose water. The indicated series of metals can be quite strictly composed if the conditions are clearly defined. It is in this way that a series of stress is built. By their ability to combine with oxygen, metals can be put in a row that starts with the most noble metal - gold, and ends with the most reactive alkali metals - sodium, potassium, etc.