A child begins to cry after a blood test. “What’s wrong?” asks the mother. “The nurse took my blood,” wails the child, “and she didn’t give it back!” The child, unaware that his body was capable of replenishing the lost blood, believes that he needs the blood back to be healthy and strong.

Students come to science with a lifetime’s worth of misconceptions about the world of science. Although teachers in earlier grades may have dispelled some notions, others may be difficult to shake.

Most misconceptions that students hold about science are not so obvious or easy to detect. Students may believe that

• all disease is caused by the same kind of germ
• the matter from dead organisms simply disappears as it rots away
• the Earth’s atmosphere acts like a greenhouse and traps heat

Students may not understand that

• people on the “bottom” of Earth don’t fall off
• chemical changes are reversible
• plants produce their own food

• Everyday language can cause misconceptions. For example, students may have seen their parents buy or administer “plant food” and so believe that plants need food to grow.
• Lack of evidence leads students to form mistaken conclusions. Because students cannot see germs or microscopic organic materials without a microscope, they may not grasp the concept.
• Word of mouth, the media, and speculation all spread misconceptions. Students may believe that the atmosphere acts like a greenhouse because this idea is conveyed in newspapers, in adult conversations, and on the Internet.
• Confusion over concepts can create wrong impressions. Students who compare and contrast physical and chemical changes may believe that because physical changes are reversible, chemical changes are irreversible.

The first step in dispelling misconceptions is to identify them and to recognize their sources.

• use open-ended questions to assess what students know about the topic of a lesson. For example, in plant science, ask students “What do we give plants to make them grow?”
• listen and observe students’ answers
• use direct questioning to discover the students’ reasoning process

• Help students formulate a theory first.
• Set up an experiment next. For example, to demonstrate chemical change: Dip a heat-sensitive baby spoon and other objects that might change color into a beaker of hot water. Ask students to record their observations or results. Students might notice that a baby spoon turned white when it was dipped in hot water and returned to its original color as it cooled. Ask students questions that will help them evaluate the results and draw new conclusions: “Did the baby spoon undergo a reversible chemical change?”