Grade 10.docx

 We observed that, as evidenced by the formation of bubbles, a change took place when we dropped the packet containing the baking soda in both flasks. We also observed that the mass in the open flask decreased after the packet was dropped.  Below shows that the gas evolved is carbon dioxide. The f...

 We observed that, as evidenced by the formation of bubbles, a change took place when we dropped the packet containing the baking soda in both flasks. We also observed that the mass in the open flask decreased after the packet was dropped.  Below shows that the gas evolved is carbon dioxide. The formation of bubbles, which means that gas was being evolved. In the open flask, bubbles were formed because carbon dioxide gas was formed escaped from the flask. On the other hand, the carbon dioxide gas formed was trapped inside the flask that was stoppered with the cork. The gases that were formed from the reaction in each flask also have mass. The mass of the gases accounts for the mass that appeared to be missing in the open flask. We can see that when matter undergoes chemical change or chemical reaction, the mass of the substances before and the mass of the substances after the reaction are equal. We say that the mass of the matter undergoing chemical change is conserved. This leads us to the first law of matter, the law of conservation of mass. Another way to express the law is to say that \"Matter can neither be created nor destroyed by chemical means." In 1797, French chemist Joseph-Louis Proust reacted several elements with oxygen, and based on his observations, he concluded: \"I shall conclude by deducing from these experiments the principle I have established at the commencement of this memoir, viz. that iron like many other metals is subject to the law of nature which presides at every true combination, that is to say, that it unites with two constant proportions of oxygen. In this respect it does not differ from tin, mercury, and lead, and, in a word, almost every known combustible. Whenever 100-g samples of iron are reacted with oxygen, they will always react with 115g of oxygen. In terms of percent by mass, iron contributes 46.51% and oxygen 53.49%. Similarly, different samples of the same compound of iron and oxygen will invariably contain 46.51% iron and 53.49% oxygen. This means that if you take 1.0 g or 1.0 kg of the compound, the compound will always yield 46.51% iron and 53.49% oxygen. This result will happen only if elements are made of small particles that have the same masses. These observations are summed up in the form of another law, the law of definite composition. The law of definite composition states that any sample of a compound would invariably have the same proportions by mass of its constituent elements. Chemistry is similar to cooking. In cooking, you can use the same ingredients and come up with different dishes. For example, a cake can be made from flour, eggs, baking powder, and water. The same ingredients can also be used to make pancakes, crepes, and even lumpia wrappers. It all depends on the proportion of each ingredient. Similarly, in chemistry, elements can also form different compounds using the same type of elements. John Dalton, expanding on Proust\'s work, found out that 100 g of tin can react with either 13.5 g or 27 g of oxygen. He noticed that the amount of oxygen used is in a ratio of 1:2. This result, along with countless others, led Dalton to propose the law of multiple proportions. Unit IV discusses Dalton\'s atomic theory. The law of multiple proportions states that if two elements can combine to form more than one compound, the masses of one of the elements that combine with a mass c\' the other element are in fixed ratios of whole numbers. For example, 100 g of carbon combines with either 133.3 g or 266.6 g of oxygen. Another example is hydrogen and oxygen, which can form H2O (water), and H2O2 (hydrogen peroxide). Think of two elements A and B as particles. If A and B form different compounds, 1 and 2, then the mass of A in each compound will always be an integer multiple of the mass of a single particle of A. Since the particles of A have the same mass, the ratio between the mass of A in compound 1 and the mass of A in compound 2 will always be an integer or a simple fraction. This is in congruence with results of experiments. **Dalton's Atomic Theory** **Democritus** **Democritus called those small pieces of matter as "atomos", the Greek word for indivisible. ** **Although his theory was remarkable, it was rejected by Aristotle, and the atomic theory was ignored for 2000 years. ** **Democritus' suppositions about the atoms were not useful in explaining the chemical phenomena because there were no experiments to support them.   ** **Joseph Priestly, Antoine Lavoisier, and others set the stage for the foundation of chemistry.  ** ***"ATOMS ARE INDESTRUCTIBLE."*-John Dalton, 1803** ***Atoms can still contain smaller particles and that these subatomic particles further contain particles within.  *** By using experimental methods, John Dalton (1766-1844), a chemist and school teacher in England, revived and revised Democritus ideas and turned them into a scientific theory. Dalton\'s atomic theory is based on these postulates: 1\. Elements are composed of small particles called atoms. 2\. Atoms of an element are identical, having the same properties such as mass, size, and chemical properties. Compounds are composed of atoms of at least two different elements, and the ratio of each element is an integer or a simple fraction. For example, carbon dioxide has 1 carbon atom and 2 oxygen atoms, and their ratio is 1 is to 2. A chemical reaction results from the rearrangement of the atoms of reacting substances, giving new combinations of atoms. Atoms can neither be destroyed nor created in a chemical reaction All of these postulates are based on the three laws of matter. The fourth postulate is simply a restatement of the law of conservation of mass, while the other postulates are based on the law of definite composition and the law of multiple proportions. In Dalton\'s work, he thought that atoms are indestructible. However, it was later found that atoms still contain smaller particles and that these subatomic particles further contain particles within them. Since then, some revisions have been made on Dalton\'s work although much of it remained intact Have you ever noticed an annoying \"static cling\" effect when pulling a plastic tape from a roll? Or have you looked at a flash of lightning during a thunderstorm? All of these phenomena are caused by particles within the atom. In this lesson, we will uncover these secrets and delve into the world inside the atom.