![]() ![]() Law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. What happens in the reaction flask? Do you think that a chemical reactionhas taken place? Why should we put a cork on the mouth of the flask?ĝoes the mass of the flask and its contents change? Now tilt and swirl the flask, so that the solutions X and Y get mixed.Weigh the flask with its contents carefully. ![]() Hang the ignition tube in the flask carefully see that the solutions do not get mixed.Take a little amount of solution of Y in a conical flask and some solution of X in an ignition tube.Prepare separately a 5% solution of any one pair of substances listed under X and Y in water.Take one of the following sets, X and Y of chemicals– X Y.Is there a change in mass when a chemical change (chemical reaction) takes place? Activity 1 The following two laws of chemical combination were established after much experimentations by Lavoisier and Joseph L.Proust. Lavoisier laid the foundation of chemical sciences by establishing two important laws of chemical combination. All this was based on philosophical considerations and not much experimental work to validate these ideas could be done till the eighteenth century.īy the end of the eighteenth century, scientists recognised the difference between elements and compounds and naturally became interested in finding out how and why elements combine and what happens when they combine.Īntoine L. Democritus called these indivisible particles atoms (meaning indivisible). Another Indian philosopher, Pakudha Katyayama, elaborated this doctrine and said that these particles normally exist in a combined form which gives us various forms of matter.Īround the same era, ancient Greek philosophers – Democritus and Leucippus suggested that if we go on dividing matter, a stage will come when particles obtained cannot be divided further. Ultimately, a time will come when we shall come across the smallest particles beyond which further division will not be possible. ![]() An Indian philosopher Maharishi Kanad, postulated that if we go on dividing matter (padarth), we shall get smaller and smaller particles. The idea of divisibility of matter was considered long back in India, around 500 BC. Ancient Indian and Greek philosophers have always wondered about the unknown and unseen form of matter. ![]()
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