From Atoms to Materials

gold panning 淘金 Fig. 13.24 Gold panning*: a physical method for the extraction of gold Let’s Think Put crushed gold ore in a large pan of water. 1 Shake the pan repeatedly, so that impurities (sand, stones, etc.) are washed away by water, while gold grains sink to the bottom. 2 Gold grains remain in the pan. 3 • Some metals exist as elements in their ores. They can be extracted using physical methods. • Some metals exist as compounds in their ores. They can be extracted using chemical methods. 2. Chemical methods Most metals exist as compounds in their ores. These metals have to be extracted by chemical methods. When a chemical method is carried out, one or more new substances are formed , including the metal we want to extract. Extracting gold from its ore The extraction method shown here involves a difference in a certain physical property of gold, sand and stones. What is that physical property? 67 13 From Atoms to Materials © United Prime Educational Publishing (HK) Limited 2024 All rights reserved; no part of this publication may be reproduced, photocopied, recorded or otherwise, without the prior written permission of the Publisher. Sample