Molecular Structure and Designed Materials

The molecular-level structure is important in the functioning of designed materials. Some examples include the following:

• Flexible but durable materials are made up of long chained molecules. Long polymer chains are held together by the strong orbital overlap making flexible, easily formable, and durable materials.
• Electrically conductive materials are often made of metal.
• Pharmaceuticals are designed to interact with specific receptors.

Additionally, the forces between atoms and molecules determine the properties, such as the state of matter, melting point, boiling point, vapor pressure, surface tension, malleability, conductivity and solubility.  Some examples include the following:

• The strong crystal structure of an ionic compound (transfer of electrons between metals and nonmetals) is one of the main reasons why ionic compounds have a high melting point.
• Covalent bonds (sharing of electrons between two nonmetals) are more rigid in nature.
• Nonmetals show low ductility and high brittleness. Additionally, their low malleability means nonmetals cannot be drawn or hammered without breaking.
• Malleability is the ability of a metal to be hammered into thin sheets. The free electrons enable the atoms to move and roll over each other.

Also, the intermolecular forces and polarity of molecules affect why a material will be used for a specific purpose. 

​Below, you will find several examples of how molecular structure is important in the functioning of designed materials.

Diamond Versus Graphite

Graphite and diamond are allotropes of carbon. An allotrope is when two or more different physical forms exist for a given element. Graphite and diamond are both made of carbon, but we can write with soft graphite, and we are unable to write with a diamond. Why is this? Watch the following video: ​https://kcts9.pbslearningmedia.org/resource/nvtoe-sci-diagraph/wgbh-nova-treasures-of-the-earth-molecular-structures-of-diamond-and-graphite/.

Attribution: Diamond_and_graphite.jpg: User:Itubderivative work: Materialscientist, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons

Electrical Conductors

Electrical conductors are made up of metals, such as copper. These metals are used because metals conduct electricity and are ductile (able to be drawn out into a thin wire).

Attribution: ​Marekich, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Instant Hot and Cold Packs

To make instant hot and cold packs, you need four ingredients: a type of salt, water, a small bag, and a large bag. When salt dissolves in water, it can make a hot or cold pack. It all depend on what type of salt (ionic compound ) you use. Check out the following video! (Note: Do not try this.)

https://youtu.be/A5q0NUDbGp8

Pots and Pans

Attribution: Drmarathe, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

The pots and pan can't be reactive. You don't want your food tasting different. Also, pots and pans need to be able to conduct heat well. Due to this, metals are used to make pots and pans. The common metals that are used are copper, aluminum and stainless steel (iron, chromium and carbon). The main property of metals is that it can absorb heat, and it is malleable, so it can keep its shape when heated up. Additionally, when pans are made, plastic is added to the handle because plastic does not conduct heat as well as metals. Since metal is a great conductor of heat, it is necessary to use plastic, so you do not get burned when touching the pan. 

Fireworks

When you look at a firework show, you see several different colors. This is due to the different metals that are used. When a metal atom is placed into a fire, the electron absorbs energy and moves from the ground state to the excited state, but the falls back to the ground state. When the electron falls back to the ground state, energy is released. Check out the following video to learn more about fireworks!

https://youtu.be/nPHegSulI_M

Disposable Diapers

Diapers are made to absorb urine. This is due to a polymer called sodium polyacrylate. Sodium polyacrylate absorbs the urine. Check out the following experiment!

https://youtu.be/VTU3JNAlOG8

Waxes

• Car wax mostly contains beeswax and carnauba wax. These long hydrocarbons are hydrophobic and repel water causing rain to bead up and run off the car.
• The leaves and fruits of many plants have waxy coatings, which may protect them from dehydration and small predators.
• The feathers of birds and the fur of some animals have similar coatings which serve as a water repellent.

Soap

Do you ever wonder why soap works? Water molecules have strong intermolecular forces. Also, soap has a polar end and non-polar end, so how does soap work? Check out the following video!

https://youtu.be/6WunMIp9huM

Other Products​

• Pick a product/material that is not listed above.
• What is the molecular structure of the substance that is important to the functionality of the chosen material?
• For some help with this, go to the following website: https://ptable.com/#Compounds. You can create compounds and see what they are used for.