1. Observing Chemical Properties
A chemical property is any ability to produce a change in the composition of matter. Flammability and reactivity are two examples of chemical properties.

2. Observing Chemical Properties
Flammability
Materials that burn can be used as fuel. Flammability is a material’s ability to burn in the presence of oxygen.
Reactivity
The property that describes how readily a substance combines chemically with other substances is reactivity.

3. Observing Chemical Properties
Rust forms when oxygen reacts with iron and water. Rust is a brittle, reddish-brown compound. Because iron is highly reactive, you would not choose iron to make jewelry or coins.

4. Recognizing Chemical Changes
The color change in a banana peel is caused by chemical changes that are taking place in the cells of the banana. A chemical change occurs when a substance reacts and forms one or more new substances.

5. Recognizing Chemical Changes
The color change in a banana peel is caused by chemical changes that are taking place in the cells of the banana. A chemical change occurs when a substance reacts and forms one or more new substances.

6. Recognizing Chemical Changes
The color change in a banana peel is caused by chemical changes that are taking place in the cells of the banana. A chemical change occurs when a substance reacts and forms one or more new substances.

7. Recognizing Chemical Changes
A Change in Color
A change in color is a clue that a chemical change has produced at least one new substance.
A new copper roof and an old copper roof have different colors.

8. Recognizing Chemical Changes
A new copper roof has a reddish color.

9. Recognizing Chemical Changes
A new copper roof has a reddish color.
The green patina on an old copper roof is a mixture of copper compounds.

10. Recognizing Chemical Changes
Production of a Gas
When you mix vinegar with baking soda, bubbles of carbon dioxide form immediately. A similar chemical change happens when you use baking powder as an ingredient in a cake recipe. Bubble of carbon dioxide expand and cause the cake to rise.

11. Recognizing Chemical Changes
Formation of a Precipitate
Any solid that forms and separates from a liquid mixture is called a precipitate. When an acid is added to milk, proteins in the milk undergo a chemical change that causes them to stick together in clumps and form a precipitate–cottage cheese.

12. Is a Change Chemical or Physical?
Are different substances present after a change takes place? If not, then the change is physical, not chemical.
When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter remains the same.

13. Which of these properties is a chemical property of sulfur?
Assessment Questions
Which of these properties is a chemical property of sulfur?
yellow
flammable
brittle
soft

14. Which of these properties is a chemical property of sulfur?
Assessment Questions
Which of these properties is a chemical property of sulfur?
yellow
flammable
brittle
soft ANS: B

15. Assessment Questions
Which of the following is not a common type of evidence for a chemical change?
a change of state
a color change
a gas produced
a precipitate formed

16. Assessment Questions
Which of the following is not a common type of evidence for a chemical change?
a change of state
a color change
a gas produced
a precipitate formed ANS: A

17. You can be certain that a chemical change has occurred when
Assessment Questions
You can be certain that a chemical change has occurred when
there is a visible change.
the change is irreversible.
the temperature changes.
a new substance is formed.

18. You can be certain that a chemical change has occurred when
Assessment Questions
You can be certain that a chemical change has occurred when
there is a visible change.
the change is irreversible.
the temperature changes.
a new substance is formed. ANS: D