Introduction to metals S2 Chemistry Classifying chemicals and chemical reactions

Examples of metals How many different metals can you write down the name of in 2 minutes? What do these metals have in common? What might be different about these metals? This is all about getting students to share prior knowledge/understanding/misconceptions about metals. It should put what follows in a context. There are alternative ways to do this e.g. in a KWL grid. As part of the discussions, the word “properties” should come up. Students should know about properties of metals from the S1 course. This is an opportunity to revise these. It would be helpful to remind students what is meant by the term “property” (what something looks like or what it can do) and to emphasise the difference between physical properties from chemical properties. PHYSICAL PROPERTIES IN COMMON Shiny Malleable Good conductors of heat and electricity PHYSICAL PROPERTIES WHICH ARE DIFFERENT e.g. Colour (gold and copper are the only metal elements which are not silver) State at room temperature (mercury is a liquid) / melting and boiling point Density CHEMICAL PROPERTIES WHICH ARE DIFFERENT e.g. Reactivity with other substances (oxygen, water, acid) OTHER THINGS WHICH COULD BE IDENTIFIED AS DIFFERENT: How abundant they are Value Use Elements or not elements (alloys)

Learning outcomes Success criteria Know examples of uses of metals. You can describe five different uses of metals, including: a brief description of the use the name of the metal used Given information about physical and/or chemical properties, you can suggest a suitable metal for a particular use.

Of the 90 naturally occurring elements, 70 are metals.

Gold

Silver

Nickel

Sodium

Mercury

Bronze Bronze is an alloy

Key question Why are metals important? Metals are important because of the variety of things we can use them for. 2. Metals come from the Earth’s crust. Most metals are not found naturally as the metal element but as a compound of the metal. Exceptions include gold and silver. 3. Aluminium 4. It depends on the metal. Some are very reactive (e.g. potassium) and some are unreactive (e.g. gold)

Uses of metals You need to match the use of a metal with a property that makes it suitable for that use. Why is copper used in electrical wiring? Why is aluminium used to build aeroplanes? Why is gold used in jewellery? Why is aluminium used to make saucepans? Why is iron used to build bridges? COPPER – conducts electricity well ALUMINIUM – low density GOLD – unreactive; malleable ALUMINIUM – conducts heat well; does not react with water IRON - strong

Silver is a better conductor than copper Silver is a better conductor than copper. Suggest why it is not used in electrical wiring. Which of the metals in the table is not an element? Present this information in a bar graph.

Learning outcomes Success criteria Know examples of uses of metals. You can describe five different uses of metals, including: a brief description of the use the name of the metal used Given information about physical and/or chemical properties, you can suggest a suitable metal for a particular use.

Learning outcomes Success criteria Understand the occurrence of metals in nature. You can state how many of the elements occur naturally as metals. You can state whether most metals occur naturally as elements or as compounds.

Key questions Where do metals come from? Which metal is the most common on Earth? How reactive are metals? Metals are important because of the variety of things we can use them for. 2. Metals come from the Earth’s crust. Most metals are not found naturally as the metal element but as a compound of the metal. Exceptions include gold and silver. 3. Aluminium 4. It depends on the metal. Some are very reactive (e.g. potassium) and some are unreactive (e.g. gold)

Compounds of metals Most metals are not found naturally as the element but as part of a compound. An example is shown. (These metal compounds are called ores, but that will be discussed in a future lesson).

This Periodic Table (larger version available in the Chemistry department) shows elements (and therefore metals) which are found only as compounds, as both compounds and as the element, and as just the element.

Metal found in nature as… Element only Element and compound Compound only Element only e.g. gold Element and compound e.g. copper, silver, mercury, platinum Compound only e.g. sodium, magnesium, aluminium, iron, zinc, nickel (and many more)

Key question What does this information on how the elements exist tell you about how reactive they are? Add an arrow to your table to illustrate this point. Those found as elements only are the least reactive; those found as element and compound are more reactive; those found as compounds only are more reactive still.

Metal found in nature as… Element only Element and compound Compound only Element only e.g. gold Element and compound e.g. copper, silver, mercury, platinum Compound only e.g. sodium, magnesium, aluminium, iron, zinc, nickel (and many more) Increasing reactivity

What are the 10 most common elements in the Earth’s crust?

Make a copy of this list and highlight the metals. Make clear to students that these elements all occur as compounds. Make a copy of this list and highlight the metals. Make a pie chart to illustrate the abundance of the first five elements in this list, grouping the rest as “others”.

Learning outcomes Success criteria Understand the occurrence of metals in nature. You can state how many of the elements occur naturally as metals. You can state whether most metals occur naturally as elements or as compounds.