cbseclass11chemistrychapter1somebasicconceptsofchemistry-210709141537 (1).pptx

cbseclass11chemistrychapter1somebasicconceptsofchemistry-210709141537 (1).pptx

1. CBSE Class 11 Chemistry SOME BASIC CONCEPTS OF CHEMISTRY

2. What is Chemistry? It is the scientific study of the structure of substances and what happens to them in different conditions or when mixed with each other. Molecules

3. (i.e ., Imperial System) The Metre Convention also known as the Treaty of the Metre, is an international treaty that was signed in Paris on 20 May 1875 by representatives of 17 nations (Argentina, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Ottoman Empire, United States of America, and Venezuela ). The treaty created the  International Bureau of Weights and Measures (BIPM) , an intergovernmental organization under the authority of the  General Conference on Weights and Measures (CGPM) and the supervision of the  International Committee for Weights and Measures (CIPM) , that coordinates international metrology and the development of the metric system.

4. According to the new convention of 2019

5. Hierarchy table of SI System Density Triangle

6. Volume Density

7. SCIENTIFIC NOTATION RULES Scientific notation is a standard way of writing very large and very small numbers so that they’re easier to both compare and use in computations. Every number in the scientific notation must be in the form of  : a x 10 n where  1 ≤ a < 10  and  n  must be a positive or negative integer . To convert a number into scientific notation, first we have to identify where the decimal point and non zero digit come.  There are two cases in it.  Case 1 :

8. To move the decimal point to the left, we have to count number of digits as explained in the example given below. According to the example given above, we have to move the decimal point 3 digits to the left and exponent of 10 should be 3 (positive integer) When we do so, we get the scientific notation of the given number. So , 2301.8 = 2.3018 x 10 3

9. Case 2 : To move the decimal point to the right, we have to count number of digits as explained in the example given below. According to the example given above, we have to move the decimal point 5 digits to the right and exponent of 10 should be -5 (negative integer) When we do so, we get the scientific notation of the given number. So , 0.000023 = 2.3 x 10 -5

10. Important Note:  If we don't find decimal point at anywhere of the given number, we have to assume that there is decimal point at the end of the number. For example , 2300000 -------------> 2300000 . Here, the non zero digit comes first and decimal point comes next. So we have to apply case 1 to convert this number into scientific notation.   Practice Problems : Write the given numbers in scientific notation. 0.00006 5400000 71 x 10 2 33 x  10 -3 0.63 x 10 -3 Solutions 6 x 10 -5 5.4 x 10 6 7.1 x 10 3 3.3 x 10 -2 6.3 x 10 -4

11. For Example,

12. Example 1.644 has four significant figures 1.6044 has five 0.0054 has two 1500. has four a nd 1500.0 has five (for number 1500, there are two as, can be written as 1.5 )  

13. Multiplication and Division The result must contain the same number of significant figures as in the value having the least number of significant figures.

14. 1.25 ft.

15. Laws of Chemical Combination 1. Law of Conservation of Mass - It states that matter can neither be created nor destroyed. This law was put forth by Antoine Lavoisier in 1789. 2. Law of Definite Proportions - This law was given by, a French chemist, Joseph Proust. He stated that a given compound always contains exactly the same proportion of elements by weight.

16. 3. Law of Multiple Proportions - This law was proposed by Dalton in 1803. According to this law, if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element, are in the ratio of small whole numbers.

17. 4. Gay Lussac’s Law of Gaseous Volumes - This law was given by Gay Lussac in 1808. He observed that when gases combine or are produced in a chemical reaction they do so in a simple ratio by volume provided all gases are at same temperature and pressure.

18. 5. Avogadro Law - In 1811, Avogadro proposed that equal volumes of gases at the same temperature and pressure should contain equal number of molecules .

19. Average Atomic Mass Many naturally occurring elements exist as more than one isotope. When we take into account the existence of these isotopes and their relative abundance (per cent occurrence), the average atomic mass of that element can be computed. For example, carbon has the following three isotopes with relative abundances and masses as shown against each of them.

20. 48.00 u

21. u

22. (for gas)