13.4Q) Leather

Covalent bonding is chemical bonding from...?

• ...the attraction of positive metal ions and delocalized electrons.

• ...sharing of electron pairs between atoms.

• ...the transfer of electrons between atoms.

• ...the attraction between electronegative atoms and lone pairs.

Tags

NGSS.HS-PS1-1

Covalent bonding gets stronger if...

• ...there are more delocalized electrons.

• ...there are more shared electrons.

• ...the size of the atoms get bigger.

• ...the mass of the atoms get bigger.

Tags

NGSS.HS-PS1-1

Covalent bonds require...

• ...high energy to break.

• ...moderate energy to break.

• ...low energy to break.

Tags

NGSS.HS-PS1-4

Hydrogen bonding is chemical bonding from...?

• ...the attraction of positive metal ions and delocalized electrons.

• ...sharing of electron pairs between atoms.

• ...the transfer of electrons between atoms.

• ...the attraction between electronegative atoms and lone pairs.

Which mechanical properties have high values in most leather?

• Viscoelasticity

• Malleability

• Density gradient

• Grain structure

• Tear resistance

Categorize:

Groups:

(a) Macroscopic

,

(b) Microscopic

,

(c) Atomic/Molecular

,

(d) Subatomic

• Triple helix structure

• Fibre network

• Non-metal elements

• Hydrophilic/-phobic interactions

• Covalent bonds

• Tanning proces

• Porosity

• Cross-linking

• Fatliquoring

• Density gradient

• Type of collagen fibrils (I, III, IV)

• Hydrogen bonds

Match the following

• Triple helix structure

• the nonpolar (repellent) interactions with water, influences the water-resistance and permeability properties of leather

• Type of Collagen

• the polar (attractive) interactions with water, influences the water-resistance and permeability properties of leather

• Cross-linking

• The chemical bonds that connect the polymer chains in elastomers, providing stability and memory of the relaxed state

• Hydrophilic interactions

• The arrangement of three α polypeptide chains in a helical conformation that makes up the collagen molecules, which are the fundamental building blocks of the leather structure

• Hydrophobic interactions

• make up the fibrous structure of leather, with type I providing high strength and types III and IV forming the fine-grained structure of the grain

Match the following

• Porosity

• The highly cohesive three-dimensional structure of interweaving collagen fibre bundles that gives leather its distinctive properties

• Density Gradient

• The measure of how tightly the woven structure of leather is, which affects its water vapour and air permeability

• Tanning process

• The chemical treatment that enhances the strength of leather by linking the collagen fibrils through the formation of chemical bonds, preventing the fibrils from moving apart

• Fatliquoring

• The variation in density from the grain (outer surface) to the reticular layer (reverse side) of the leather, with coarse fibres in the central region providing high strength

• Fibre network

• The process of making the leather fibres and fibrils slippery, which improves the softness and physical properties of the material

Tags

NGSS.HS-PS1-4