Material Decay Investigation
Big Idea
Not all materials survive the same way. Organic materials, like plants and wood, naturally decompose over time, while many inorganic materials, such as stone and metal, are much more resistant to decay. The materials ancient people chose—and the environments where those materials were stored—help determine what archaeologists can still discover thousands of years later.

Materials

• Small pieces of different materials, such as:
  • Notebook paper
  • Cardboard
  • Cotton fabric
  • Popsicle stick or small piece of wood
  • Leaf
  • Small rock
  • Aluminum foil
  • Plastic (optional)
• Small clear cups or jars
• Water
• Labels or masking tape
• Science notebook or recording sheet

Optional: Potting soil and small containers if you would like to compare decomposition in soil instead of water.

What to Do

Step 1: Make Predictions
Examine each material.
Predict which materials will change the most over time and which will stay almost the same. Write down your predictions before beginning the experiment.

Step 2: Set Up the Investigation
Place one sample of each material into its own labeled cup or jar.
Add enough water to cover each sample.
Place all of the containers in the same location so they experience similar conditions.
(Optional: Instead of water, bury each sample in damp soil to compare how materials decompose underground.)

Step 3: Observe Over Time
Check your samples every few days for several weeks.
Look for changes such as:

• Softening
• Color changes
• Mold growth
• Breaking apart
• Swelling
• No visible change

Record your observations with notes or drawings after each observation.

Step 4: Compare the Results
At the end of the investigation, compare your observations with your original predictions.
Ask yourself:

• Which materials changed the most?
• Which stayed almost exactly the same?
• Were your predictions correct?
• Which materials would make the best writing surfaces if you wanted someone to read your message 2,000 years from now?

What's Really Happening (Caregiver Explanation)
Organic materials come from living things, so bacteria, fungi, and other decomposers can break them down over time. Water speeds this process by creating conditions that allow decomposers to grow and spread. Inorganic materials, such as stone and many metals, are much more resistant to decomposition because they are not made from living tissue.

This simple investigation helps explain why archaeologists find thousands of clay tablets and stone carvings but relatively few ancient books made from bark, papyrus, cloth, or wood. It also demonstrates why climate matters: the same papyrus scroll that might survive for thousands of years in Egypt's dry desert could completely decompose in a humid rainforest.

Digging Deeper
Imagine you are an ancient scribe who must preserve an important message for people living 2,000 years in the future. Based on your investigation, what material would you choose, and where would you hide or store it to give it the best chance of surviving? Explain your reasoning using evidence from your experiment.