Physical Properties of Metals Pure metals allow their ions to slide over each other, a characteristic shown in the provided table and figure. Alloys like brass and steel are created by mixing metallic elements with others to enhance strength and prevent deformation. The differing sizes of ions in alloys inhibit sliding, improving shape retention compared to pure metals. Reactivity Series Highly reactive metals like potassium and sodium react vigorously with cold water, while others react more slowly. Metals above hydrogen in the series can react with dilute acids to produce salts and hydrogen. The reactivity of metals influences their ability to displace other metals from compounds. Ionic Equations and Displacement Reactions Magnesium can displace copper due to its higher reactivity, forming positive ions more readily. Zinc powder heated with copper(II) oxide demonstrates a similar displacement reaction. No reaction occurs when zinc oxide is heated with copper,