Importance, properties and qualities of metals
People have used metals such as iron, copper, tin, silver, gold and lead since ancient times. Today machines, machine tools, building parts and household things are made from them. Properties of metals fall into three groups: physical (for example density, heat and electrical conductivity), mechanical (strength, hardness, elasticity) and technological (forgeability, weldability, machinability). In industry metals are usually used not pure but as alloys: cast iron, steel, bronze, brass and duralumin are examples. Items are made by rolling (passing the metal between counter-rotating rollers) or by casting. A craftsman who makes things from metal is called a chilangar (metalworker/locksmith).
Hunt game: each pair writes in the notebook 5 metal objects at home (spoon, lock, wire, bucket, key) and guesses the metal they are made from. Answers are compared in class. At home look only at objects an adult shows you; nothing is taken apart.