Change

Change is all around us, even if you don't realize it; when it rains, when you cook dinner, when you’re in chemistry class. There are two different types of change- physical changes and chemical changes.
Physical changes are more obvious because things often look different after a physical change occurs. A physical change is defined as when the form of a substance, or even some of its properties change, but its chemical composition- the way it’s atoms are put together- remains unchanged. Examples of this are mixing sugar into your tea, breaking a stick, putting fruits in a blender to make a smoothie, and even when fog forms on your bathroom mirror after a shower.


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A chemical change is defined as when elements recombine to form new chemical compounds with new and different properties. Fireworks are a good example of a chemical change. This is because the firework starts being made up of different kind of explosive powders, then the powders are ignited and burn, combining with oxygen, and give off different colored light.

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The Rock Cycle

Scientists believe that the Earth began as a melted mixture of many different materials. It is believed that these materials went under many physical changes, that eventually, over time became the Earth we know today.

Igneous rock is formed by melting, and then cooling and solidifying. This kind of rock is usually created by volcano magma. This is a very slow change that still happens today. This kind of rock is concidered "new".


This may someday become Igneous Rock
This may someday become Igneous Rock


Weathering is constantly breaking down rocks. Some examples of weathering are wind or water blowing over rock, carrying away tiny bits of it at a time; even when gravity makes a rock fall and break apart. When these bits of rock are carried to another place, the small pieces can build up and, under much heat and pressure, sedimentary rock can be formed. Sedimentary rocks aren’t “new” when formed. They are made of bits and pieces of old rocks. You can often tell if a rock is sedimentary because it will often have visible layers of different materials, appearing striped.

Sedimentary Rock
Sedimentary Rock

When a tectonic plate moves, it can bring rocks from the surface down, closer to the core, making the old rock melt, and start again as igneous rock. It can also bring rocks from deep in the crust up onto the surface, causing them to erode and form sedimentary rock.


The Rock Cycle
The Rock Cycle


Practice Time! Highlight for the answers.

1.) List all the changes, both physical and chemical, that you can think of that happens when an average candle burns.
As the candle is burning, the condle gets shorter. The elements in the wax and wick combine with oxygen in the air, when combusted, and burn into the air.
2.) Which of the following is a difference between a chemical change and a physical change?
A. Physical changes are more common than chemical changes
B. Chemical changes create new matter, while physical changes only work on existing matter.
C. The masses of the products in a chemical change cna exceed the masses of the reactants. In physical changes the masses are identical before and after change.
D. The chemical composition of materials is different after a chemical change but the same after a physical change.
ANSWER: D

3.) Water evaporating is what kind of change and why?
Physical, the chemical composition isn't changed.
4.) What kind of rock is "new"?
Igneous



Source: Blue TAKS Practice Book