0Topic: Chemical Changes and the Role of OxygenLearning Objective:
Students will describe changes that happen to materials in the presence or absence of oxygen, and understand why oxygen is essential for chemical changes like burning.
Introduction:
Have you seen a candle burning, wood turning to ash, or iron rusting? These are changes that happen with the help of oxygen.Key Concepts:Burning is a chemical change: Wood, paper, candles turn to ash and release gases when burned in air (which contains oxygen).Rusting is another change: Iron left in air and water turns brown (rusts) due to oxygen.Absence of oxygen: If you cover a burning candle with a glass jar, the flame stops because no more oxygen can reach it.Simple Activity:
Take a small piece of paper and burn it with adult help. Observe what happens.Cover the burning paper with a glass jar. Notice the fire stops—oxygen is needed!Leave an iron nail in a bowl of water for two days. It rusts—oxygen causes this change.Discuss with students: What will happen if fruit is left open to air?Ask students: Why is oxygen important for burning?Takeaway:
Chemical changes like burning, rusting, or browning of fruit need oxygen. Without oxygen, some changes do not happen.
Practice Questions:
• Why does a candle stop burning when covered by a jar?What is rust?
• How is it formed?Name one change that happens with oxygen and one without it.
• Why should we be careful around fire and chemicals?
Assessment:Worksheet
• fill-ins based on today's lesson.Share an example of chemical change observed at home.
