Description of the Experience
Opis skúsenosti Silver- Argentum, its name is connected with Argentina. According to information the biggest manufacturer of silver jewellery is Mexico. At that time but also today is made silver cutlery or its part because it is very impractical, because silver changes its colour and you have to take care of it. That does not mean that it changes its chemical properties, it belongs to noble metals. The most commonly it is used for manufacture of jewellery. Pureness of silver is usually 925 so it is mellow metal. In some countries is still kept the tradition of manufacture of silver jewellery. It is inherited from one generation to another. Once I saw this kind of jewellery workshop right in the shop. The technique is called filigree and it is similar to lace. Jeweller has a silver wire and makes jewelleries.
Sodium- Natrium, Potassium-Kalium, belong to alkaline metals. They do not have typical metal properties, they are mellow and can be cut by knife. It is not possible to touch them with hands because they seriously damage skin, they are caustic. Most commonly is used sodium, in compound NaCl or sodium chloride or salt which we daily use. NaOH or sodium hydroxide is strong hydroxide, it is alkali and in contact with textile it makes a hole to it, in contact with skin it caustic burns. The old people called this compound lye, it was used in manufacture of soap and that is why two generations in past did not apply soap on face.
In my laboratory I also have NaOH, it looks like white pills but considering the amount of students it is possible to do only demonstrative experiments.
Calcium-Ca,calcium, it is biogenic element which means that it is found in living organism and it is necessary for good state of bones. The most known is its compound calcium carbonate or also called limestone. Whole blocks of mountains are made of it and luckily we still have school trips to caves so students can easily imagine it. Calcium is also part if the shell of bird eggs.
Tin-Stannum,Sn, is known metal, even students know it because they use it for connecting of materials. In past it was used for manufacture of cups, mainly beer was drunk from it. Tin occurs in two forms – white and grey. It is very interesting fact because at temperature lower than 13 degrees white tin changes to grey tin and we can easily see it because it turns into powder. When the tin was discovered it was used for manufacture of buttons for army uniforms. After one cold night the soldiers woke up and had no button on their uniforms. Also so called scream of tin exists which is created during bending tin wire as a result of its inner structure.
Curriculum does not allow us to give enough interesting information about metals to students because only minimum amount of lessons is devoted to it.
The students are not interested in simple fact as oxidation numbers, manufacture of ores from metals. I bring some publications to lessons for them, for example many books is devoted to gold. Last year a great book Elements was published where each of elements is shown in the way it actually looks and students are interested in it.
In order to post a comment it is compulsory to be logged in.
