1, chalk, also known as blackboard pen and whiteboard pen, is a common writing tool. The production process of chalk includes mixing, grinding, sieving, pressing and molding.
The main feature of chalk is that it is soft and easy to wipe, so it is widely used in educational occasions. When writing on the blackboard, chalk powder can quickly blend into the gaps on the surface of the blackboard to form a uniform coating. Over time, the written content can be removed by wiping, which is convenient for teaching demonstration and modification.
3. Chalk has good environmental protection performance, because it does not contain toxic and harmful substances and will not cause harm to the environment and human health. However, chalk will produce dust during use, and long-term inhalation may lead to respiratory diseases. Therefore, when using chalk, we should pay attention to protective measures, such as wearing a mask and keeping indoor ventilation.
In recent years, with the development of science and technology, a new type of chalk called "dust-free chalk" has appeared. Dust-free chalk adopts special production technology, which makes the powder more delicate and uniform and produces less dust when writing. In addition, dust-free chalk can also be dissolved in water, which is convenient for cleaning and reuse.
Concept and related knowledge of calcium carbonate
1. Calcium carbonate is an inorganic compound with the chemical formula CaCO? . It is one of the most common minerals on the earth and exists in many biological and natural environments, such as coral, shells, limestone, calcite and marble.
2. Calcium carbonate is a stable isotope of calcium, and its crystal structure consists of a cation (calcium ion Ca) and an anion (carbonate ion CO? There are many forms of calcium carbonate in nature, such as aragonite, calcite and aragonite. These minerals can be used as building materials, industrial raw materials and feed additives.
3. Main uses of calcium carbonate, building materials: Calcium carbonate is an important part of building materials such as cement, concrete and mortar. Because of its high hardness, good wear resistance and low cost, it is widely used in the construction industry.