Grade 11 CBC/CBE Chemistry: Relative Atomic Mass Step by Step

Why is chlorine 35.5 and copper 63.5, when no atom has a mass like that? In this Grade 11 CBC/CBE Chemistry lesson you will learn what relative atomic mass compares, why it is measured against one twelfth of a carbon-12 atom, and why it has no units. You will see why it is a weighted average of the isotopes, calculate it step by step, and then work backwards to find how much of each isotope an element contains. The lesson ends with how a mass spectrometer measures these values. FREE REVISION PAPER FOR THIS LESSON Paper 1: Core concepts Download it here: https://drive.google.com/file/d/13MtN... IN THIS LESSON 0:00 Hook and title 0:34 In this video 1:19 Atoms are too light to weigh 1:52 Comparing with a standard 2:42 The carbon-12 standard 3:21 Weighing an atom against slices 3:56 Why there are no units 4:48 Remember isotopes 5:31 A weighted average 6:21 The same idea with class marks 7:13 Worked examples: chlorine and magnesium 8:25 Why so few whole numbers? 9:11 Relative atomic mass and the mole 10:04 Working backwards: a seesaw 11:07 Worked example: copper 12:22 Worked example: boron 13:23 Your turn: why no units? 13:55 Your turn: lithium 14:51 Your turn: gallium 16:04 Working backwards: a ratio 17:09 Find the mistake 18:05 Watch out for these mistakes 19:06 What to remember 20:02 Going further: the mass spectrometer 21:01 Challenge and next video YOUR CHALLENGE Element Q has two isotopes, Q-121 and Q-123, and a relative atomic mass of 121.8. Find the percentage of each isotope. Then give the ratio of the heights of its two peaks in a mass spectrum. Write your answer in the comments. PREVIOUS LESSON Lesson 1: What is a mole? :    • Grade 11 CBC/CBE Chemistry: The Mole Conce...   NEXT LESSON Lesson 3: Relative formula mass and molar mass. How do you find the mass of one mole of water, salt or sugar? ABOUT SP-SciLearn SP-SciLearn makes paced, interactive science and math lessons for Kenyan learners following the CBC/CBE curriculum. Every lesson stops so that you can try a question yourself before the answer appears. Subscribe and turn on notifications so that you do not miss the next lesson. Grade 11 CBC/CBE Chemistry · 1.1 The Mole #Grade11Chemistry #CBEKenya #Chemistry