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  Lesson 1–3: The Properties of Matters and their Classification We have to use various materials in doing different works. We use thousands of materials, starting with the water to wash our hands and face just after getting up from bed in the morning. We use various types of food, crockery, clothes, toy, stone, cycle, football, marble, book, etc. Of these, some are soft, some are hard, some are shiny, some are round and some are flat. But all of them are matters. All of these materials occupy space and have mass. So, we can say that things which occupy space and have mass are called matters. However, the volume of some very small particles of matters is negligible. There are numerous types of matters in the world and they are classified in various ways. Among these, one of the classifications is based on the state of the matter. Let us take an example. When a piece of ice is kept in a pot, what happens? It is converted into water. Again we can convert the water into vapour by heat...

  May Day or International Workers' Day is observed on May 1 all over the world today to commemorate the historical struggle and sacrifices of the working people to establish an eight-hour workday. It is a public holiday in almost all the countries of the world.   Since the Industrial Revolution in the 18th and 19th centuries in Europe and the US, the workers in mills and factories had been working a long shift, fourteen or even more hours a day.   On May 1st in 1886, inspired by the trade unions, half of the workers at the McCormick Harvesting Machine Company in Chicago went on strike demanding an eight-hour workday. Two days later, a workers' rally was held near the McCormick Harvester Machine Company and about 6000 workers joined it. The rally was addressed by the labour leaders. They urged the workers to stand together, to go on with their struggle and not to give in to their bosses. At one point of the rally, some strike breakers started leaving the meeting p...