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Montessori Biology

Materials That Undergo Decay: Biodegradable and Nonbiodegradable Materials

Quick elementary science lesson and free worksheets on materials that undergo decay, biodegradable vs. nonbiodegradable waste, and the importance of decomposition.


Have you ever wondered what would happen if things didn’t decay? What would happen to a forest, for example, if the fallen leaves of trees just kept piling up?

Decay seems like an unpleasant process, because things that are decaying or rotting usually don’t look or smell nice. Think: mold on bread, worms on fruit, the bodies of dead animals. But decay is absolutely essential to the balance of the world. Life as we know it would not exist without the yin and yang of growth and decay.

To decay is to be slowly destroyed into bits in the presence of water, air and soil. (Definition from DepEd module)

Some materials are capable of being broken down or decomposed to smaller products by the action of living things such as animals or microorganisms. This process of decay, rot, or decomposition is carried out by decomposers such as:

  • Fungi 
  • Bacteria 
  • Invertebrates (worms and insects) 

Examples of materials that undergo decay include paper, food waste, tree leaves, twigs, and things made of plant-based cloth (natural cotton, hemp, bamboo, silk, abaca, jute).

Once they are broken down, they are easily absorbed into the soil to become nutrients for plants — the inorganic matter in soil is derived from plants and animals — or transformed into other useful materials.

One example of dead things being transformed by microorganisms into some other useful thing is fossil fuels.

Fossil fuels are a type of fuel that was formed over millions of years from the decomposing remains of plants and animals. These remains were acted upon by microorganisms, fossilized, compressed, and heated underground, until they acquired their current form. Coal, petroleum/oil, and natural gas are all examples of fossil fuels. Whenever you ride a vehicle that runs on gasoline or use electricity generated from coal, you are actually benefiting from the transformative power of decay. (That said, fossil fuels create their own environmental problems and must not be used mindlessly — but that’s a lesson for another day.)

  • Signs a material is decaying:
    • Foul odor
    • Presence of molds
    • Presence of worms
    • Formation of bubbles
  • Factors that contribute to the decaying process:
    • Sunlight
    • Water
    • Soil
    • Action of microorganisms
  • Leftover food is kept in refrigerators to avoid/delay spoilage since the microorganims that break down food do not grow fast in cold temperatures.

Nonbiodegradable Materials

Think again about what would happen to a forest if the leaves that fell from its trees never decayed.

And think about what would happen to the earth if nothing ever decayed.

In fact, there are lots of things in the world right now that don’t decay.

And because they don’t decay — because they don’t get broken down and transformed into other useful things — once they are waste, we are stuck with them. That’s why it’s really important for everyone on earth to be mindful about the waste they produce.

  • Materials that do not decay — substances that cannot be broken down by decomposers into their natural components — are called nonbiodegradable materials.
  • 3Rs of waste management:
    • Reduce – minimizing the amount of waste produced
    • Reuse – using objects again and again
    • Recycle – using waste materials to create new products

Materials That Undergo Decay: Worksheets

Note on the Worksheets

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Select the Pictures of Materials That Undergo Decay: Worksheet

Note: You can download a free printable version of this worksheet here: Pictures of Materials That Undergo Decay Worksheet (PDF)

Materials That Undergo Decay Worksheet: Biodegradable or Nonbiodegradable

Note: You can download a free printable version of this worksheet here: Materials That Undergo Decay – Biodegradable or Nonbiodegradable Worksheet (PDF) 

Materials That Undergo Decay: Grade 4 Worksheet

Note: You can download a free printable version of this worksheet here: Materials That Undergo Decay – Grade 4 Worksheet (PDF) 

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