Understanding Matter – Maharashtra Board Class 9 Solutions for Science and Technology (English Medium)
Lavoisier, a French chemist, on the basis of quantitative studies, classified substances into elements and compounds. He showed that when mercuric oxide is heated, it changes into mercury and oxygen.
Mercuric oxide is a compound because it decomposes into two substances. But mercury and oxygen cannot be further decomposed into simpler substances; hence, they are elements.
- False. Water is a compound as hydrogen and oxygen are combined in a fixed proportion.
- False. Milk is a heterogeneous mixture as components are not in a fixed proportion.
- False. Brass is a mixture as components are not in a fixed proportion.
Brass. Others are elements.
Carbon. Others are mixtures.
- Filtration: Take a mixture of sand and sugar in a beaker. Add water to it and stir well. Filter the solution. Sand will remain on the filter paper as it does not dissolve in water. If the filtrate is slowly heated, water evaporates and sugar crystals will remain in the container.
- Hand picking: If the sand is fine and sugar crystals are big enough, then they can be separated by picking up by hands.
Table salt is a compound of the elements sodium and chlorine, which are poisonous. However, these constituents do not retain their individual properties when they are chemically combined to form a compound. Thus, a compound has totally new properties than the constituents, and it is not poisonous. Hence, we can eat table salt without getting poisoned.