Appendix 4
Reading to Learn
4B ‧ Ch.14 Changes of Matter ‧ p.44
Matter Decay
香港資訊 Science for You
Matter decay is one of the most important processes in nature. The process includes complicated changes. When we leave food waste out for a while, it becomes soft in texture and dull in colour. Sometimes we can even find mould on it. This is the process of food decay. One of the main causes of food decay is that some microorganisms overgrow in food. They break down food and turn it into simpler matter. The matter nurtures the soil and provides nutrients for growing crops and other plants. As such, the matter recycles in nature, ensuring a continuous supply of agricultural products to humans.
root
breakdown further in the soil
breakdown
absorbable nutrient
food waste
compost
In the food chain, animals also produce ‘food waste’ after they hunt, which are similar to the food waste we produce after we handle and eat food. The remains of eaten and dead animals, and the animals’ faeces will be broken down by microorganisms in the end. Therefore, the microorganisms are also called ‘decomposers’. Plants absorb the nutrients in decayed matter to grow. These plants become food for plant-eating animals, and plant-eating animals become food for meat-eating animals. As a result, matter in the food chain is transformed continuously, helping animals and plants survive and reproduce.
food chain in nature
eaten by
eaten by
plants
rabbit
wolf
In summary, matter decay is the key to the balance of nature. It facilitates the recycling of matter and maintains a balanced ecosystem. We should learn more about this amazing process of natural cycle.
Let’s Think
1. Is matter decay a physical change or a chemical change? 2. How does matter decay affect humans and nature?
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