What substances have the highest and lowest thermal conductivity? Where are they used?

Vacuum has the lowest thermal conductivity, which is used, for example, in everyday life (thermos), in science and industry (when storing reduced gases in Dewar vessels). In general, substances with low thermal conductivity are used as heat insulators, for example, air, as a poor heat conductor is used to insulate houses, it is contained between the glass windows and prevents houses from cooling in winter.
Metals conduct heat well, silver and copper are especially high thermal conductivity. Substances that conduct heat well are used as heat exchangers, for example, to remove heat from car engines.