Lesson 23
Properties of Different Materials
Building on Lesson 21, learners investigate how scientists identify and describe materials using observable and testable properties. Students use their senses to gather clues, perform physical tests including hardness, weight, flexibility, and elasticity comparisons, and explore special tests including the magnetic test and conductivity. They apply this knowledge to explain why specific materials are chosen for specific jobs.

Key Ideas
  • The right material for a job is chosen because its specific properties match what that part of the object needs to do. There is often no single best material, only the best material for a specific situation.
  • The magnetic test distinguishes iron and steel from other metals. Only iron and nickel are attracted to a magnet.
  • Flexible means a material can bend without breaking and stays in its new shape. Elastic means it returns to its original shape after bending or stretching. Brittle means it breaks instead of bending.
  • Materials have physical properties that can be tested: hardness, relative weight, flexibility, elasticity, and conductivity.
  • We identify materials using all five senses together: appearance, texture, surface feel, temperature response, and sound.
Vocabulary
  • Conductivity: How well a material allows heat or electricity to pass through it. All metals conduct both heat and electricity.
  • Malleable: Describes a material that can be shaped or molded without breaking. Wet clay and heated metal are malleable.
  • Brittle: Describes a material that breaks instead of bending. Glass and dried clay are examples.
  • Elasticity: The ability to return to the original shape after bending or stretching. Rubber is the most elastic common material.
  • Flexibility: The ability to bend without breaking. A flexible material stays in its new bent shape.
  • Hardness: How well a material resists being scratched or dented.
Sources
Lesson23_Properties_of_Materials.pptx by Selene
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