Diamonds vs. Spider Silk Crystals and Polymers

Do you remember which molecules represent a solid? The molecules of most solids form regular shapes through repeating patterns.

Two Types of Solids Crystals (Diamonds) Polymers (Spider web silk)

Crystalline Solids Crystals (crystalline solids) have molecules that form a regular, repeating pattern. These patterns create crystals. In general, crystalline solids do not get soft when heated. Examples of crystalline solids are sugar, salt, and diamonds.

The Molecules in Crystalline Solids Diamonds Graphite (pencil lead) Atoms Because they are the same element – Carbon. Diamond because it has more bonds between its atoms. What do the round structures represent? Why are all the atoms the same color? Which substance is more hard? Why?

Diamond vs. Graphite What is similar about these substances? Both diamonds and graphite are made of the same atoms, carbon; despite having distinct physical properties. What accounts for their different physical properties (hardness, luster, density, etc)?

Two Models of Salt Molecules What kind of observations can you make about the molecular structure of salt? Student should observe that atoms are arranged in repeating patterns and can not change position. Students should also note that there are 2 different types of atoms (Sodium and Chlorine). There are 2 different types of atoms arranged in repeating patterns that can’t change position.

Polymers A polymer is a large, repetitive, string-like molecule. Most organic structures are polymers made of Carbon, Hydrogen, Oxygen, and/or Nitrogen.

The Molecules in Polymers What are some characteristics of these structures? Cotton Students should notice the structures are long repetitive chains Silk

Cotton and Silk What are some similarities between cotton and silk? Where do all polymers come from? Polymers come from organic (living or once-living) things like plants, petroleum, and animals.