Science activities can put geologic time scales in perspective.
Science activities and demonstrations engage students in ways that textbooks just can't match. Elementary students are enthusiastic participants in science activities, whether they are performing the experiment or watching it as a member of the audience. The most important role of the science teacher is to get them involved and thinking about science.
Geologic Time Activity
The large numbers used when talking about geologic time often means that students really don't quite comprehend the extent of billions of years. Teachers can aid comprehension by using a model that is familiar to most students. A football field works well because of its familiarity and the 100-yard length is easy to work with. Divide 4.6 billion years (Earth's age) by 100. Each yard on the football field is equal to 46 million years, and a 10-yard section of the field is equal to 460 million years. Draw a football field on a large piece of paper, or even make a bulletin board into a football field. Begin the time scale at 4.6 billion on the left of the paper, and mark off 10-yard sections with vertical lines. Draw horizontal lines to show geologic eras on the field, starting on the left with the Hadean Era (4,600 to 3,800 million years ago), followed by the Archaean Era (3,800 to 2,500 million years ago), the Proterozoic Era (2,500 to 543 million years ago), the Paleozoic Era (543 to 248 million years ago), the Mesozoic Era (248 to 65 million years ago), and the Cenozoic Era (65 million years ago to present). Students now have a better idea of the geologic time scale. The eras can be split into periods in order to be more detailed. Students finish the activity by placing events on the time line. Students can research each era and find important events to add to the time line. Two examples are first microscopic life (3,600 million years ago) and the disappearance of the dinosaurs (65 million years ago). Students place these events on the time line with a paragraph explaining the event.
Collapsing Can Demonstration
This demonstration is designed for students to learn the importance of observational techniques and air pressure. Materials include an empty, undented can; a bowl of cold water; a heat source; a dark cardboard background; and tongs. The dark background allows students to see the steam from the boiling water. Tell students to carefully watch and document everything that happens in the demonstration. Place one tablespoon of water in the can, and heat it until it boils and steam appears. Take the can off the heat with the tongs, and carefully (so as not to burn youself) invert it into the bowl of cold water. The can will immediately collapse. Instruct students to write their key question and offer a hypothesis as to why the can collapsed. Test several of these. If the students do not realize that the can collapsed because of pressure differences inside and outside the can, they can research this demonstration and find the answer.
Dancing Raisins
Students learn about the fizz in soda and why objects heavier than water can float. Materials include fresh raisins; a tall, clear glass; and a can of colorless soda. Pour the soda into the glass. Bubbles rise to the surface. These come from the carbon dioxide gas released from the soda. Drop six raisins into the glass. They will sink to the bottom. After a few minutes, they should begin to rise. This is because the soda is carbonated and releases carbon dioxide bubbles. The bubbles will stick to the rough surface of the raisin and lift it because of an increase in buoyancy. When the raisin reaches the top, the bubble will burst, and the raisin will sink back down. It should rise again as a carbon dioxide bubble attaches to it. This will continue until the carbon dioxide is expended or the raisin becomes saturated with liquid and thus too heavy to rise. Have students try this activity with several other substances; some with rough surfaces and some with smooth surfaces. Have them record their activities. After they finish, ask them to explain why the raisins rise to the surface. Provide research material so that they can find the answer to this question.
Tags: million years, carbon dioxide, football field, events time, events time line