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Science Connections
Chapter 3 Section 3

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1.5 class periods

3-3 Chemical Properties and Changes

In this section students will learn that the physical and chemical properties of a substance are useful in determining the identity of a substance. The properties that distinguish one substance from another without changing the substance are called physical properties. The properties that describe how a substance changes into another new substance are called chemical properties. Students will investigate flammability, or the ability of a substance to burn, as a chemical property. They will discover that the substance produced by the burning is a new substance that has been altered by the chemical change. Thus flammability is a chemical property, and burning is a chemical change. They will note that another name for a chemical change is a chemical reaction.

The themes that can be focused on in this section are energy, patterns of change, and systems and interactions.

Energy: Point out that substances can be made to change phase by adding or taking away energy, but that in a chemical change energy is released from or added to the particles making up the old substance to create the particles making up the new substances. Sometimes energy must be added to produce a chemical change, and sometimes a chemical change releases energy. Breaking up water into hydrogen and oxygen is an example of the first. The burning of hydrocarbons is an example of the second.

Patterns of change: Explain that a chemical change effects a change in the particles of a substance. Point out that the particles of a substance are indeed made of smaller particles that do not undergo a change when they are rearranged to form the new substances.

Systems and interactions: Note that during a chemical reaction, new substances with different physical and chemical properties are produced. Two or more substances, each with its own physical and chemical properties, interact under certain conditions to produce one or more new substances, each with its own physical and chemical properties.

Performance Objectives 3-3

  1. Distinguish between physical and chemical properties of matter.
  2. Explain how chemical properties are useful in identifying substances.
  3. Define and discuss the chemical property of flammability.
  4. Discuss the chemical property of the ability to support combustion.
  5. Distinguish between a chemical property and a chemical change.

Science Terms 3-3

Chemical property, p.76

Flammability, p.76

Chemical change, p.77

Chemical reaction, p.77

Show students a wooden splint.

  • What is this object made of?

Light a match and set the splint on fire. Let it burn until at least half of it has become charred or has fallen off as ash.

  • What changes do you see in the part of the splint that burned?
  • Do you think the identity of the original substance has changed?

Point out that chemical properties describe ways in which substances change into other substances.

  • What chemical property of wood did you observe in the demonstrations with a wooden splint?
  • What is another name for this property?

Light a small candle, in a holder, then blow it out.

  • What did the match do?
  • What combined with the wick and wax to cause combustion?
  • Where did the oxygen come from?

Re-light the candle, cover the candle with a 500-mL beaker.

  • What happened?
  • Why did the flame go out?

  • Give two examples of chemical properties.
  • What is chemical change? Give an example.
  • Suppose you visited another planet and wanted to test a sample of the planets air. What kinds of test would you perform to determine some physical properties of your sample? What kinds of tests would you perform to determine some chemical properties?