In this easy fossil experiment, students explore how fossils are formed. Students simulate mineral replacement to show how bones become hardened fossils. During the lab students observe how salt (a mineral) is absorbed and hardens (replacing bone) “fossilizing” a sponge.
Easy Fossil Experiment: Fossil Sponges
This lab addresses SEP.2 Develop and/or use models to describe and/or predict phenomena.
Materials per student:
- sponge cut in half
- lab sheet
- scissors
Materials per group:
- small plastic container or disposable aluminum pan
- play sand
- salt
- Sharpie marker
- warm water, paper towel
- plastic spoons
- pitcher to mix salt water
- tall kitchen spoon for stirring
- paint brushes for brushing off sand (optional)
Procedure:
1.Place students in small groups. Use plastic containers or aluminum ones if you plan to put them in the oven.
2. Use a marker to draw a fossil shape on the sponge. Cut out the shape.
3. Put about 2 inches of sand in the bottom of the container.
4. Mix the salt water. For each group start with 2 parts salt to 5 parts warm water in a large cup or a pitcher. The water should be saturated with enough salt that it no longer dissolves, and you have some in the bottom of the cup or pitcher. (Remind students that salt is a mineral.)
5. Dip the sponge into the salt water. Without squeezing out the water, place the sponge on the sand.
6. Gently put enough sand on top of the sponges so they are completely covered. About 1 inch of sand is ideal. Slowly pour the salt water on top of the sand until it completely soaks the sand.
7. Place the container in a warm, dry place (like a sunny window) until the sand dries completely. To speed up drying time place the pan (only if you used a non-plastic, oven-safe pan) in the oven at 250 degrees for 2-3 hours.
8. Once the sand is completely dry, students carefully excavate the sponges with a spoon.
9. Place the sponge fossil on a paper towel. Students use the grid on their lab sheet to record where each fossil in their group was found in the pan.
10. Optional: Use a paintbrush to gently clean the sand off of the fossils.
Students should observe how the sponge has hardened and turned “bonelike”. Discuss how the salt filled the pores of the sponge and when the water evaporated, the salt remained in those pores. This simulates how dissolved minerals replace the cells in bones and wood.
Teacher tips:
This easy fossil experiment uses inexpensive sand called Play Sand available at home improvement stores like Lowe’s or Home Depot. You can also find play sand on Amazon. Be sure to get play sand rather than sensory sand.
It can take up to 10 days for the water to evaporate and the sponges to dry and “fossilize”, even in a sunny area. To speed things up you can use aluminum baking pans from the dollar store instead of plastic containers and place the containers with the buried sponges in an oven at 250 degrees F for a few hours.
Detailed lesson plan about fossils
This easy fossil experiment is part of a complete 3rd grade science unit, Environment, Survival, and Fossil Evidence.
Carefully designed to align with 3rd grade NGSS Unity and Diversity strand and standards 3-LS2-1, 3-LS4-1, 3-LS4-2, 3-LS4-3, 3-LS4-4, it includes 25 days of highly engaging science lessons on these topics:
- Adapting to Survive
- Physical and Behavioral Adaptations
- Survival of Individuals
- Survival of Groups
- Survival in a Changed Environment
- Fossil Evidence
- Types of Fossils
- How Fossils Form
- The Fossil Record
- The Geologic Time Scale
Each ready-to-teach lesson is detailed and scripted and centers around highly engaging lesson slides. This complete resource includes a student workbook, differentiated quizzes and unit test, hands-on investigations, and STEM activities.
This high quality, resource is available in a digital version with audio lessons and in a money-saving bundle of both formats. Preview Environments, Survival & Fossil Evidence units here.
I hope you’ll try this easy fossil experiment with your students to explore how fossils form. For more third grade science lessons, STEM activities, and science experiments visit these blog posts:
Environments & Survival Activities and Lesson Ideas
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