Phases of Matter

I’m sure you’re already familiar with the 3 phases (states) of matter so I’ll just summarize them.

1. Solid

• has a definite shape
• has a definite volume
• very difficult to compress
• particles packed close together and held rigid

2. Liquid*

• follows the shape of its container
• has a definite volume
• difficult to compress
• particles are close together but are free to move

3. Gas*

• has no definite shape
• has no definite volume; fills its container
• easy to compress
• particles are far apart
  
  
  *Liquid and Gas are considered fluids because of their ability to flow.
  
  You may have heard of the fourth state of matter- plasma. Written below are two definitions. They have the same meaning but the second one is more concise:
  
  - Plasma is a hot gas in which atoms are partially broken down to form charged particles or ions.
  - Plasma is a gas that is partially or completely ionized.
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  There are several factors which determine the state of matter. They are:
  
  1. The nature of the particles of matter
  2. Types of chemical bonds present in the matter (we'll tackle chemical bonds later on)
  3. Temperature
  4. Pressure
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  Matter is capable of changing from one phase to another. Most of the time, this happens because of a change in temperature. Here are the 4 phase changes of matter:
  
  1. Solidification
  - Liquid to solid
  - Happens when there is a decrease in temperature causing particles of liquid to lose kinetic energy, move closer together, and may eventually solidify.
  - Ex. Water freezes into ice
  
  2. Melting
  - Solid to Liquid
  - Happens when there is an increase in temperature causing the kinetic energy of solid particles to increase. If enough energy is absorbed by the solid, its particles will break away from nearby particles and posses liquid properties.
  - Ex. Ice melts into water
  
  3. Vaporization
  - Liquid to gas
  - Occurs when there is an increase in temperature causing the kinetic energy of liquid particles to increase. If enough energy is absorbed by liquid, its particles will break away from nearby particles and become gas.
  - Ex. Boiling water until it vaporizes
  
  4. Sublimation
  - Solid to gas
  - Happens when solid changes to gas without passing the liquid state
  - Ex. Mothballs & Dry ice
  

Properties of Matter

There are two properties of matter namely, physical & chemical properties. Physical property is something you can observe without changing the composition of matter. For example, you saw a jar and you said, “That jar is smooth, shiny, and 10 inches in diameter”. Smooth, shiny, and 10 inches are all physical properties of the jar. Physical property can further be divided into two: extrinsic & intrinsic properties. Extrinsic property describes the outside appearance of objects. Smooth & shiny are extrinsic properties of the jar, while 10 inches is the intrinsic property because it describes the measurable aspects of an object.

Physical changes are changes that alter a substance with out changing its composition. An example is melting & solidification. We all know that ice is solidified water. When ice melts, voila! You still have water! Another example tearing a piece of paper; even if you tear the paper into a million tiny pieces, those tiny pieces is still (yep, that’s right!) paper! Boiling water is also a physical change.

Chemical property can be observed when there is a change in the composition of matter (chemical change). An example is burning. When we burn wood, both physical and chemical changes occur. First, you may see the color, shape, & size changing, and then eventually the wood becomes ashes. Rusting & cooking are also examples of chemical changes.

Here are some signs of chemical change:
- formation of gas
- formation of precipitate (insoluble substance)
- liberation or absorption of heat
- distinct change in color
- production of flame
- presence of bubbles

Sometimes, physical & chemical changes are accompanied by endothermic or exothermic reactions. In an endothermic reaction, heat is absorbed by the substance; while in an exothermic reaction, heat is released by the substance to the environment. An example of endothermic reaction is photosynthesis. Plants absorb the heat of the sun in order to make food. Using this example, we can say that in an endothermic reaction, the reactants have lower energy contents than the products (there is an increase in the temperature of the substance). On the other hand, the solidification of water into ice is an exothermic reaction. The reactants have higher energy contents than the products (there is a decrease in the temperature of the substance).

Homogeneous and Heterogeneous Systems

We are about to discuss homogeneous and heterogeneous systems, but first, what is a system? In chemistry, a system is any group of atoms, molecules, ions, & substances. A system can either be homogeneous or heterogeneous. In a homogeneous system, substances are combined such that the components are not easily distinguished by the naked eye. Alcohol solution and sea water are examples of this type of system. To us, sea water is nothing but water. However, it is composed of many minerals, which we cannot see.

In a heterogeneous system, substances are combined such that their components are easily distinguished and their distribution is not constant. An example is a mixture of marbles and beads. In the mixture, you can easily tell apart the marbles from the beads. A terrarium is also a heterogeneous system.

Can you think of other examples of a homogeneous and heterogeneous system?