Physical and Chemical Changes
Matter can change. Some changes to matter are called physical changes. During a physical change, the substance remains the same.
For instance, you can change paper by cutting it, but it is still paper. When you freeze water, the molecules are still water; nothing changed. Every phase change -- from solid to liquid, from liquid to gas, and vice-versa - is a physical change.
A chemical change, on the other hand, occur when atoms rearrange and come together to form one or more new substances with new properties. During a chemical change, there is also a change in energy, such as the production of heat or light.
A chemical change, on the other hand, occur when atoms rearrange and come together to form one or more new substances with new properties. During a chemical change, there is also a change in energy, such as the production of heat or light.
Nature also faces many chemical changes. And not just from forest fires... Living things, for instance, have a life cycle that usually ends in death and decomposition. The thing to keep in mind is, even though the substances' atoms recombine and change, the atoms themselves are the same. The majority of the atoms in the Earth have been there for millions of years (with exception of some meteors). A Carbon atom inside you today may be inside a tree in a hundred years; the Hydrogen in the water you drink today was around since before the time of the dinosaurs, and was probably inside several different types of animals before.
Many people since the beginning of humanity, including First Peoples, observed chemical changes in their environment. Through observations and experience, they learned how they could use chemical changes in their lives.
They saw, for instance, how the skin of an animal changed when left under the Sun, and slowly developed a tanning process involving scraping, stretching and smoking the hide, to make it last a long time and become pliable and resistant to rot and wear.
They saw, for instance, how the skin of an animal changed when left under the Sun, and slowly developed a tanning process involving scraping, stretching and smoking the hide, to make it last a long time and become pliable and resistant to rot and wear.
In our sheltered modern lives, so detached from nature, we have somewhat lost the ability to observe changes around us and understand what they mean. This has proven to be a very serious issue, one that may become fatal for us as a species. Our disconnect to nature and our inability to see changes and understand their significance has caused the climate crisis, the water crisis and all that we are facing around the world.
Chemical changes are happening inside our bodies all of the time; when we digest food, when we breathe, and even inside the cells, when the oxygen produces energy for us to live.
Some chemical changes can be harmful to our bodies. On our teeth, for instance, the bacteria that live in our mouths feeds on pieces of food and eliminates acids, which dissolves the tooth enamel. Cavities are a result of chemical changes. Tanning is another chemical change created as your body tries to make a pigment to protect you from the Sun's harmful rays.
Do you think that getting your ears pierced is a physical or a chemical change?
How about dying your hair? Physical or chemical?
Chemical changes are happening inside our bodies all of the time; when we digest food, when we breathe, and even inside the cells, when the oxygen produces energy for us to live.
Some chemical changes can be harmful to our bodies. On our teeth, for instance, the bacteria that live in our mouths feeds on pieces of food and eliminates acids, which dissolves the tooth enamel. Cavities are a result of chemical changes. Tanning is another chemical change created as your body tries to make a pigment to protect you from the Sun's harmful rays.
Do you think that getting your ears pierced is a physical or a chemical change?
How about dying your hair? Physical or chemical?
The final takeaway of this unit is, the matter in this Earth is fixed. Every atom that you see today has always been there in one form or another, combined with other atoms to form different molecules, in an infinite ballet of possibilities.
This has implications for how we use this matter. For instance, if we misuse or pollute drinking water, then those molecules of H2O will be locked in until they evaporate; this often takes longer if the molecules are stuck with pollution or wasted.
What we do with matter affects how long it will be before we can use it again. How might we change how we use materials to become a more sustainable planet? Consider how a more Earth-conscious existence might benefit future generations.
This has implications for how we use this matter. For instance, if we misuse or pollute drinking water, then those molecules of H2O will be locked in until they evaporate; this often takes longer if the molecules are stuck with pollution or wasted.
What we do with matter affects how long it will be before we can use it again. How might we change how we use materials to become a more sustainable planet? Consider how a more Earth-conscious existence might benefit future generations.
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