States of Matter
Gases, liquids and solids are all made up of microscopic particles, but the behaviors of these particles differ in the three phases. The following figure illustrates the microscopic differences.
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Microscopic view of a gas. | Microscopic view of a liquid. | Microscopic view of a solid. |
* Particles in a:
* gas are well separated with no regular arrangement.
* liquid are close together with no regular arrangement.
* solid are tightly packed, usually in a regular pattern.
* Particles in a:
* gas vibrate and move freely at high speeds.
* liquid vibrate, move about, and slide past each other.
* solid ...view middle of the document...
Chemical changes, on the other hand, cause a substance to change into something entirely new. Chemical changes are typically irreversible, but that is not always the case. It is easier to understand the difference between physical and chemical changes with examples.
State changes are physical. | Phase changes are when you melt, freeze, boil, condense, sublimate, or deposit a substance. They do not change the nature of the substance unless a chemical change occurs along with the physical change. |
Cutting, tearing, shattering, and grinding are physical. | These may be irreversible, but the result is still composed of the same molecules. When you cut your hair, that is a physical change, even though you can't put the hair back on your head again. |
Mixing together substances is physical. | For example, you could mix salt and pepper, dissolve salt in water, or mix molten metals together to produce an alloy. |
Gas bubbles forming is chemical. | Not to be confused with bubbles from boiling, which would be physical (a phase change). Gas bubbles indicate that a chemical reaction has occurred. |
Precipitates forming is chemical. | When dissolved substances are mixed, and a cloudy precipitate appears, there has been a chemical change. |
Rotting, burning, cooking, and rusting (for example) are chemical. | The resulting substances are entirely new chemical compounds. For instance, wood becomes ash and heat; iron becomes rust; sugar ferments into alcohol. |
Changes of color or release of odors (i.e. release of a gas) might be chemical. | As an example, the element chromium shows different colors when it is in different compounds, but a single chromium compound will not change color on its own without some sort of reaction. |
Release/absorption of energy (heat, light, sound) is generally not easily categorized. | Hot/cold packs involve dissolving a salt in water to change its temperature (more on that in later chapters); popping popcorn is mostly (but not completely). |
Physical (Properties and Changes)
Physical Property: A physical property is one that is displayed without any change in composition. (Intensive or Extensive)
1. Intensive: A physical property that will be the same regardless of the amount of matter.
* density: m/v
* color: The pigment or shade
* conductivity: electricity to flow through the substance
* malleability: if a substance can be flattened
* luster: how shiny the substance looks
2. Extensive: A physical property that will change if the amount of matter changes.
* mass: how much matter in the sample
* volume: How much space the sample takes up
* length: How long the sample is
Physical Change: Change in which the matter's physical appearance is altered, but composition remains unchanged. (Change in state of matter)
* Three main states of matter are: Solid, Liquid, Gas
* Solid is distinguished by a fixed structure. Its shape and volume do not change. In a...