Summary

Atomic Theory

“All things are made up of atoms.”

States of matter

Solid, liquid, gas, and plasma

State of Solids

  • Has definite shape and volume
  • High density and not very compressible
  • Does not depend on the shape of the container (doesn’t fill it in)

State of Liquids

  • Has a fixed volume
  • Takes the shape of container
  • Less dense than solids
  • Almost incompressible

State of Gases

  • Takes the shape of the container
  • Takes the volume of container (this means that the gas molecules can be spread out evenly in the container or compressed in a smaller container. The volume is when the molecules are evenly distributed.)
  • Can be compressed
  • Gases are in the gaseous state at room temperature
  • Gases have more energy than liquids, and solids.
  • Gases are less dense.

State of Plasma

Plasma is simply an ionized gas, where the gas is charged with free electrons and positive ions because of the amount of energy plasma contains.

Unit 1.1 – Properties of various states of matter.

Solids:

Picture an eraser, and try to “pour” the eraser into a beaker. Does the eraser take the shape of the container? No it doesn’t. Since it does not take the shape of the container, it has a definite shape. What about the volume? Remember volume is defined as the amount of space a substance occupies.  So since the eraser does not occupy any more or less space, the volume does not change. So it has a definite volume. What about if you were to visualize the particles inside the eraser, are they all spaced out? No, as a matter of fact, they are actually so compact that they can’t move. So if the molecules don’t have much room to move, then it must be very dense! The density of solids is a lot denser than liquids and especially gases (with the exception of water).

Water is an exception because frozen water or ice is actually less dense than liquid water. This is due to the crystal structure of the solid water form compared to the liquid form. The solid crystal form of frozen water actually provides more room between the molecules than in liquid form. Imagine if solid water were to be denser than liquid water, would we still have polar bears? Also, since all particles have energy (as long as it is above absolute zero of -273C or 0K), they must move, but because there is hardly any room for the molecules to move, they vibrate. Therefore, in all solids, the molecules, instead of bouncing back and forth on the container, the molecules are vibrating while contacting the neighbouring atom.

Solids can be broken down into two main categories: amorphous and crystalline structures.

In Crystalline structures, these are solids that have symmetry and well organized structures in their formation.

Examples of Crystalline structures are:

Covalent network such as graphite, diamond, sugar

Ionic solids (between a metal and non-metal) such as NaCl, CaCl2, CaF2

Molecular such as I2, S8

and Metallic such as Cu, Ag, Au

When crystalline structures are formed from 1 of the 4 types above, they will have an organized structure.

Amorphous structures on the other hand do not have a regular 3D arrangement of atoms. Their structures are “haphazardly” organized and lacking the symmetrical formation found in crystalline structures.

An example of amorphous structures is glass.

Summary of a solid:

  • Has definite shape and volume
  • High density and not very compressible
  • Does not depend on the shape of the container (doesn’t fill it in)

Liquids:

Take a beaker of water and pour it into another. Does it take the shape of the container?

Does the volume change before your poured your liquid compared to after you pour it in? In other words, does your liquid water take up more or less space after your pour it into the beaker? No, because the volume of water or liquid is constant or definite. But because liquids as you have observed in your water is a lot more fluid than solids, the spaces between the particles are a lot more spaced out. Thus, it is less dense than solids (exception being water). The spaces between the molecules, although larger than solids, are still insignificant enough to make compression possible. Thus, it is almost incompressible for liquids. Liquids also take up the shape of the container as well as you have demonstrated by pouring the water into the beaker.

Summary of Liquids

  • Has a fixed volume
  • Takes the shape of container
  • Less dense than solids
  • Almost incompressible

Gases:

Gases are in a category of its own since the properties of gases are so much more different than solids and liquids. First of all, picture a semi-inflated soccer ball. If you were to squeeze the soccer ball, the size of the soccer ball is decreased, because the gas inside the soccer ball is compressed. The properties of gases are so unique because the spaces between the particles are much larger than both liquids and solids that it changes the entire dynamics of gases.

The density is a lot less than solids and liquids. Furthermore, because of the spaces, gases can be compressed. Take a balloon, and blow into it. What kind of shape does the balloon take? Yes, it takes any shape the container makes. The size of the balloon will also depend on the gases, if there are a lot of gases, then it will become bigger, if there aren’t a lot of gas particles, the balloon will be ‘flat’.  What about the volume? Since the volume is the space the molecules take up, gases’ volume is the volume of the container. The gas molecules will fill up the volume of the container, thus taking the volume of the container.

When gases are trapped in a container, the gas particles according to the Kinetic Molecular Model will collide. The gas particles will travel in a straight line and move until they hit another particle and off they go to hit another particle. The type of collision the gas particles take can be of two different types: elastic and inelastic collision. In elastic collision, the particles conserve or retain its energy before and after the collision. The gas particles do not gain or lose any energy in the process of the collision but this is if and only if the temperature and pressure were to remain constant.

In inelastic collision, the particles will either lose or gain energy after the collision.  This is due to the fact that the temperature or pressure have changed in the process.

Example:

If energy before collision (E1) is greater than > energy after collision (E2), then there is an energy loss in the collision.  One scenario for this is that there is a drop in pressure (increase in volume) after the collision. Perhaps due to an inflation of a container?

If energy before collision (E1) is less than < energy after collision (E2), then there is an energy gain in the collision.  This is due to an increase in pressure or temperature during the collision.

However, if there is an equal amount of energy before and after the collision E1 = E2, then there is no gain or loss of energy, meaning that the collisions will carry on. The possibility of this is only when there is a constant temperature and pressure.

Summary of Gases

  • Takes the shape of the container
  • Takes the volume of container (this means that the gas molecules can be spread out evenly in the container or compressed in a smaller container. The volume is when the molecules are evenly distributed.)
  • Can be compressed
  • Gases are in the gaseous state at room temperature
  • Gases have more energy than liquids, and solids.
  • Gases are less dense.

Plasma:

Plasma is simply an ionized gas, where the gas is charged with free electrons and positive ions because of the amount of energy plasma contains. Neat fact is that the plasma state is actually the most common state that is found in our universe. Our sun is practically plasma!

  • Plasma is simply an unstable mixture of positive ions and electrons.
  • Can exist is at temperatures of over 100 million degrees Celsius.
  • However, plasmas are the most common form of matter in the universe, comprising 99% of the visible universe.
  • Examples are aurora borealis, lightning, stars, and plasma TVs.