Directions: Use the information provided and your knowledge of Physical Science to answer the following questions. Show all work where necessary.
Directions: Use the information provided and your knowledge of Physical Science to answer the following questions. Show all work where necessary.
A plastic grocery bag can stretch, bend, and twist without breaking, while a grain of table salt shatters when crushed. Both materials are solids, yet they behave very differently when force is applied. Scientists explain this difference by modeling how atoms are arranged inside each material.
Solids are made of atoms arranged in specific ways. Even though plastic and salt are both solids, their atomic structures are very different, which explains why they behave differently under stress.
Plastic materials, such as plastic bags, are made of long molecules called polymers. These polymers are chains of repeating units, mostly made of carbon and hydrogen atoms. The chains are flexible and can slide past one another when pulled. Because the atoms are bonded in long chains rather than locked in place, the material can stretch without breaking.
Table salt, also known as sodium chloride, is not made of long molecules. Instead, it forms an extended structure called a crystal lattice. In this structure, sodium and chlorine atoms repeat in a rigid, organized pattern that extends in all directions. Each atom is strongly attracted to its neighbors, forming a stiff framework.
When force is applied to a salt crystal, the rigid lattice cannot bend or slide. Instead, the connections break suddenly, causing the crystal to crack or shatter. This is why salt grains break apart rather than stretch.
Scientists use models to represent these atomic arrangements. Polymer models show long, repeating chains, while crystal lattice models show a repeating pattern of atoms arranged in fixed positions. These models help explain how microscopic atomic structures lead to macroscopic properties, such as flexibility or brittleness.
By comparing the atomic composition and structure of plastics and salt, scientists can explain why materials that appear similar at a large scale can behave very differently.
Diagram 1.
Source:
https://pp.one/
Diagram 2.
Source: https://www.lorric.com/en/Articles/Roechling/all/amorphous-vs-semi-crystalline
Table 1.
Material | Main Atom Types | Structure Type | Approximate Number of Atoms per Unit | Response to Pulling | Ability to Bend or Stretch |
|---|---|---|---|---|---|
Plastic (Polymer) | Carbon, Hydrogen | Molecule (Polymer Chain) | 1000 | Stretches | High |
Table Salt (Sodium Chloride) | Sodium, Chlorine | Extended Structure (Crystal Lattice) | 2 | Breaks | Low |
Graph of Information - Figure 1.
Graph of Information - Figure 2.
Which statement best describes the atomic structure of plastic compared to table salt?
Using Table 1 and Figure 1, compare the approximate number of atoms per structural unit in plastic and table salt.
The diagrams show different atomic arrangements for polymers and crystal lattices. Explain how these different arrangements affect how each material responds when pulled.
According to Table 1 and Figure 2, which material has a high ability to bend or stretch?
When force is applied, plastic stretches while salt breaks. How does the ability of polymer chains to slide past one another help explain this difference?
How does the atomic structure of plastic and salt explain why plastic can stretch while salt breaks when force is applied?
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