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In this lesson we will take a look at the 3-Dimensional world we live in. Look at the image below. You will see two points.

A line has only one dimension --length. The line has no endpoints and extends forever in both directions. That is why when a line is drawn, we see arrows at both ends. On the other hand when we draw a line segment on a piece of paper it has endpoints.

**Question 1:** How many endpoints
does a line segment have?

The line, ray and line segment are all examples of 1-Dimensional objects since they only have length.

On the other hand a square has both length and height.

**Question 3:** How
many dimensions does a square have?

A square or rectangle is really a plane, a 2-Dimensional object that has no thickness.

When we see a graph on a page we really don't think in terms of dimensions. But the graph above has only two axis or two dimensions. It is a plane.

Click on Graph to see that it only has 2-D

Each
point on the graph is represented by an x and y position. To find the x-position
we count to the right. To find the y-position we count up. Take a look at the
graph below. Angle ABC is represented by three points.

Point B has the coordinates (2,4). Starting from the origin (0,0) to reach point B we count 2 spaces to the right, then four spaces up.

**Question 4: **What are the coordinates
of point A?

Compare the graph above (showing the cube) to the one shown in the above that contains angle ABC. What is different in this graph? Besides the x-axis and y-axis what do you see?

This graph has another axis, the z-axis. When we locate a point in three dimensions we need to use three coordinates. The origin in a two dimension plot is written (0,0).

**Question
7: **How do you write the coordinates for the origin in a 3-dimension plot?

What does all this have to do with molecules? Molecules are solid 3 dimensional objects in 3 dimensional space. To describe molecules accurately we must describe their postion in 3-D space.

-------------->spin on -------->-
spin off

------>space fill/cpk
-------->stick
----> ball-and-stick

**To Rotate the Molecule**--->Left Click and Drag

**To Zoom-**->>Left Click + hold Shift button and Drag Vertically

**Jmol Menu **--->>Right-Click

**PDB File for Salt Molecule** click here.

Look at the salt crystal structure above. Each atom is represented on the x,y,z coordinate axis as a single ball.

In the next section we will look at molecules and their relationship to mathematics.

- Why is water such a good solvent?
- Why does ice float?
- Why do solids, liquids and gases behave differently?
- What is the geometry of methane?
- What's the difference between alpha and beta glucose?
- How does caffeine work in the brain?
- How does soap work?
- What is the difference between sucrose and fructose?
- Why is carbon monoxide so dangerous?
- Why is graphite so soft if it is made of only carbon?
- What is the difference between Carbyne and Graphite?
- Why is the fullerene and similar structures the cornerstone of nanotechnology?
- How big is a nanotube?
- Why does table salt have a cubic crystal shape?
- What is the structure of the benzene molecule?
- Why do carcinogens cause cancer?
- What causes Sickle Cell Anemia?
- What is the difference between sodium nitrite and nitrate?
- How do drugs work?