13 Questions
What is the primary method of determining the colligative properties of a substance?
Measuring the osmotic pressure and boiling point elevation
What is the characteristic of a polymer in the glassy state?
Brittle and rigid
What occurs at the β transition temperature (Tβ) in a polymer?
Only side groups in the polymer gain sufficient thermal energy to rotate
What is the result of the molecular chains gaining freedom to rotate at the glass transition temperature (Tg)?
The polymer adopts a random coiled conformation
What is the temperature at which an amorphous polymer changes from a glassy state to a rubbery state and vice versa?
The glass transition temperature (Tg)
What is the characteristic of a polymer in the rubbery state?
Rubbery and flexible
What is the primary characteristic of amorphous polymers in the solid state?
Transparency and brittleness
What is the consequence of the polymer molecules adopting random coiled conformations?
The polymer changes from a glassy to a rubbery state
What is the significance of the glass transition temperature (Tg) in a polymer?
It is the temperature at which segments of the polymer main chain become free to rotate
What is the purpose of measuring colligative properties in a substance?
To determine the molecular weight of the substance
What is the difference between the β transition temperature (Tβ) and the glass transition temperature (Tg)?
Tβ is the temperature at which side groups in a polymer have sufficient thermal energy to rotate, and Tg is the temperature at which segments of the polymer main chain become free to rotate
What is the common characteristic of all amorphous polymers?
They all change from a glassy state to a rubbery state on heating
What is the result of the polymer molecules being unable to move easily in the glassy state?
The polymer becomes more rigid and brittle
Study Notes
Colligative Properties
- Measuring colligative properties helps determine certain characteristics
- Examples of colligative properties include freezing point depression, boiling point elevation, osmotic pressure, and lowering of vapour pressure
Glass Transition Temperature
- Amorphous polymers in the solid state are rigid, hard, and transparent like glass (glassy state)
- In the glassy state, molecular chains cannot move easily, making the polymer brittle
- When heated, amorphous polymers undergo two transitions: β-transition temperature (Tβ) and glass transition temperature (Tg)
- At Tβ, side groups in the polymer gain sufficient thermal energy to rotate
- At Tg, segments of the polymer chain (complete blocks of C atoms) gain sufficient thermal energy to rotate as an entity
- At Tg, the polymer's behaviour changes from glassy to rubbery
- In the rubbery state, molecules adopt random coiled conformations due to free rotations about single covalent bonds in the chain backbone
- All amorphous polymers undergo a transition from glassy to rubbery state when heated, and vice versa when cooled, at a definite temperature called the glass transition temperature
Test your understanding of physical properties of polymers, including colligative properties and glass transition temperature. Learn about the characteristics of amorphous polymers in the solid state and how they behave when heated.
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