Science Discrepant Events and Critical Thinking

Using Surprising Phenomena to Focus Students’ Attention in Science

Sep 1, 2008
David R. Wetzel

Science Discrepant Event Investigation - cielo

Sample discrepant events are used to cause contradictions in students' prior knowledge and experiences in support of their better understanding of science concepts.

Science discrepant events provide opportunities for students to witness scientific events which have unexpected outcomes. This surprising phenomenon causes students to use critical thinking skills as they try to explain what happened. These events cause a contradiction in students’ way of thinking, due to cognitive disequilibrium.

Using discrepant events invokes critical thinking in students as they hypothesize reasons for what they just witnessed. As teachers provide guidance, without telling them what happened at first, students are able to develop a plausible explanation of the event. Now they are able to establish cognitive equilibrium – correct internalization of the science concept.

Teaching Strategies: Using Discrepant Events

Discrepant events typically focus on one scientific concept at a time to control for variables and to avoid conflicting resolutions in students minds. These events are created by using:

Teacher Demonstrations – student observation (least student involvement)

Student Interactions – hands-on minds-on investigation (best sensory involvement)

Videos – show a video of a scientific event for students (least sensory involvement)

Regardless of which method is used, it is important to allow students to:

Clearly observe or investigate the event

Have time to think about what they observed

Have time to discuss their observations

Have time to explain what they observed in their own words

Teachers need to listen closely for students' science misconceptions when using this teaching strategy. These science misconceptions must be addressed immediately to ensure students' correct understanding of what is happening.

These events often contradict a student’s prior knowledge and experiences and cause conflict within the student; this is why it is important to correct misconceptions immediately.

Sample Discrepant Events

Balanced Air Pressure

Materials: one aluminum pan pie (non-smooth bottom), water, one 16oz clear glass, one candle (about 3 inches tall), and matches. One set of materials for each group.

The candle is attached to the center of the bottom of the pie pan.

Water is poured into the pie pan, about three quarters inches deep.

Students light the candle.

Students place glass over the candle and observe what happens.

Allow students to repeat as necessary.

Students will observe water rising in the glass as the candle burns out.

Students will come up with many explanations; however the correct answer to the discrepant event is that:

As the candle consumes the oxygen in the glass, it creates a low pressure relative to outside the glass.

The higher air pressure outside the glass forces the water in the pie pan to move up into the glass to equalize the pressure inside and outside the glass.

Solid to Gas—Change of State

Materials: dry ice, clear container for dry ice, one large beaker, one candle (about 1.5 inches tall), and matches.

Place dry ice in clear container and allow students to observe its disappearance.

Ask students to explain what happened to the dry ice.

Provide each group with a beaker, candle, and matches.

Student light candles in the beaker.

Teacher pours enough carbon dioxide into the beaker to put the candle flame out.

Allow students to explain what they have observed.

Students will come up with many explanations; however, the correct answer is that:

The dry ice changed state directly to a gas called carbon dioxide and did not disappear. This is evidence that carbon dioxide is a clear, odorless gas, and is heavier than air. The gas displaces the oxygen and puts out the candle’s flame. Also, carbon dioxide is not a liquid at room temperature.

These and other examples of discrepant events cause students to use their critical thinking skills as they witness scientific phenomena. The events cause them to develop a better understanding of scientific concepts.

This teaching strategy is most effective when beginning a lesson on a new scientific concept and using a hands-on, minds-on approach is preferable over teacher demonstration. The optimum use of the hands-on approach forces students into conflict and then they are more likely to reveal their misconceptions openly.