# Surface Area to Volume Ratio

## Presentation on theme: "Surface Area to Volume Ratio"— Presentation transcript:

Surface Area to Volume Ratio
Principles of Physics

Volume Volume the amount of space taken up by matter is measured in m3
Objects can have the same volume but different shapes

Surface Area Surface Area the exposed size of an object
is measured in m2 Example: The surface area of a cube is equal to the sum of the areas of each of its sides.

Surface Area to Volume Ratio
All four cubes have the same volume By breaking the cube into multiple cubes the amount of surface exposed increases Suppose you broke the block into 1 nm squares. How much surface area would be exposed? 1 nm = 1/1,000,000,000 m 6 x (1/1,000,000,000 m)2 x 10729= 6,000,000,000 m2 = 1,482,632 acres 12 60,000 m2 = 14.8 acres

Surface Area to Volume Ratio
On a macro scale, the properties remain the same even if the size decreases Ex: Sugar cubes and powdered sugar both dissolve in water On a nano scale, the properties change Nano sugar may not dissolve at all For a nano sample: more atoms are at the surface because more of the sample is surface. For a macro sample: Just as many atoms can be inside as are on the surface

Which Will Burn? A steel nail? Steel wool? Why??????

Which Will Dissolve Faster?
Sugar cubes? Powered sugar? Why??????

Surface Area to Volume Ratio
The more surface area a sample has the more of it that is available to change Dissolving occurs when the solute is in contact with the solvent When iron oxidizes it creates heat (flame), more surface area more oxidation occurs because there is a greater possibility of iron colliding with oxygen

Surface Area to Volume Ratio
Example bending of a macro sample of copper occurs with movement of copper atoms of about 50 nm. Copper nanoparticles smaller than 50 nm are considered super hard materials that do not exhibit the same ductility as the macro sample.

Surface Area to Volume Ratio
Example Suspensions of nanoparticles are possible because the interaction of the particle surface with the solvent is strong enough to overcome differences in density, which usually result in a material either sinking or floating in a liquid.

Surface Area to Volume Ratio
Example Nanoparticles often have unexpected visible properties because they are small enough to confine their electrons and produce quantum effects (photons are released/absorbed when electrons move within the atom Gold nanoparticles appear deep red to black in solution.

For Example As gold goes from a bar to coins to flakes
As gold goes from a bar to coins to flakes the color remains the same As we hit the nanoscale, gold particles change in color depending on size