CK-12 Physical Science Concepts - For Middle School

2.19. Melting http://www.ck12.org

• The temperature at which a substance melts is called its melting point. The melting point of ice is 0°C.

Vocabulary

• melting: Process in which a solid changes to a liquid.

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An alloy is a mixture of a metal with one or more other substances. The followingTable2.4 lists melting points of
two metals and three alloys that they form together. Examine the table and then answer the questions below.

TABLE2.4:Melting Points of Selected Metals and Alloys

Metal or Alloy Melting Point (°C)

Iridium metal (pure) 2454

Platinum metal (pure) 1773

Platinum-iridium alloy (15% iridium) 1821

Platinum-iridium alloy (10% iridium) 1788

Platinum-iridium alloy (5% iridium) 1779

1. Based on the information in the table, what conclusion might you draw about the melting points of alloys
   relative to the melting points of the metals they contain?


2. Bronze is another alloy. It is a mixture that contains mainly copper with some added tin. The melting point of
   copper is 1084°C, and the melting point of tin is 232°C. What might be a reasonable prediction for the melting
   point of bronze?

Review

1. Define melting.


2. What happens to particles of matter when it changes from a solid to a liquid?


3. What is the melting point of a substance? What is the melting point of ice?