From Models to Materials (DP IB Chemistry)

The completed bonding triangle diagram is:

The position of a compound in the bonding triangle is determined using the electronegativity of elements and binary compounds.

More specifically using the average electronegativity and difference in electronegativity of the elements.

True.

The bonding triangle assesses the percentage of ionic or covalent character in a compound.

The average electronegativity determines the position along the x-axis of the bonding triangle.

The electronegativity difference determines the position along the y-axis of the bonding triangle.

The bonding triangle allows for a more accurate assessment of bonding type and the prediction of associated properties.

Covalent compounds are generally found at the bottom right of the bonding triangle.

The position of a compound on the bonding triangle indicates the relative proportions of ionic, covalent, and metallic character in its bonding.

A chemical with an average electronegativity of 1.1 and difference in electronegativity of 0.3 will conduct electricity.

Elements can only be classified as metallic or covalent bonding because they have an electroengativity difference of 0, which means that they are at the bottom of the bonding triangle.

Substance O is polar covalent.

Substance N is high in the ionic bonding region of th bonding triangle, which means that it will have low covalent character.

Substance M can conduct electricity when solid, because it has metallic bonding.

An alloy is a mixture of metals, where the metals are mixed together physically but are not chemically combined.

Advantages of using alloys over pure metals are:

• Greater strength

• Greater hardness

• Increased resistance to corrosion

• Increased resistance to extreme temperatures

False.

Alloys can also be made from metals mixed with non-metals, such as carbon.

In an alloy, ions of different metals are spread throughout the lattice and are bound together by delocalized electrons

Alloys can be formed due to the non-directional nature of metallic bonds.

The increased hardness and strength of an alloy is caused by the different size atoms which distort the regular arrangements of atoms, preventing the layers from sliding over each other easily.

False.

Alloys are physical mixtures of metals, where the metals are not chemically combined.

Alloys often have greater strength / hardness, or resistance to corrosion / extreme temperatures compared to pure metals.

The two main elements in steel alloys are iron and carbon.

False.

Brass is an alloy of copper and zinc.

Uses of stainless steel include:

• Cutlery

• Sinks

• Chemical plants

A polymer is a large molecule of high relative molecular mass made by linking together large numbers of smaller molecules called monomers.

A monomer is a smaller molecule that links together to form a polymer.

Monomers in a polymer are connected via covalent bonds.

A macromolecule is a relatively large molecule compared with other molecules, such as a polymer.

Examples of a synthetic polymer include:

• Resins

• Plastics

• Polystyrene (cups)

• Nylon

Examples of a natural polymer include:

• Proteins

• DNA

• Starch

False.

Some polymers contain just one type of unit, while others contain two or more different types of monomer units.

A copolymer is a polymer that contains two or more different types of monomer units.

Two examples of copolymers are nylon and biological proteins.

Linkages between monomer units in polymers include:

• Covalent bonds

• Amide links

• Ester links

The process of many monomers bonding together to form a polymer is called polymerization.

In polymer repeating units, 'n' represents the number of monomers in the polymer.

True

Polymers made from alkenes are generally non-polar and unreactive.

Polymers / plastics are often light-weight because they are low density due to the loose packing of their chains.

Polymers are strong because they contain many strong covalent bonds between the monomers / within the structure.

Addition polymerisation is a type of polymerisation in which monomers add together to form a polymer chain without the loss of any molecules.

The name of the polymer formed from the following alkene would be (poly)propene.

X is the repeating unit.

The monomer which forms the polymer is:

During addition polymerization, the π-bond in each C=C bond breaks and then the monomers link together to form new C-C single bonds.

A repeat unit is the smallest group of atoms that when connected one after the other make up the polymer chain.

In poly(alkenes) and substituted poly(alkenes), the repeating unit is the same as the monomer except that the C=C double bond is changed to a C-C single bond

Common addition polymers include:

• Poly(ethene)

• Poly(chloroethene) (PVC)

• Poly(propene)

• Poly(styrene)

A monomer must contain at least one C=C double bond to undergo addition polymerization

False.

The section of the polymer chain shown inside square brackets is the repeat unit, not the monomer.

Condensation polymerisation is a type of polymerisation in which monomers are reacted together with the loss of a small molecule, such as water.

In addition polymerisation, only the polymer molecule is formed.

In condensation polymerisation, the polymer molecule and one water molecule per linkage are formed.

The monomers have two functional groups present, one on each end.

An ester linkage is the functional group formed when a carboxylic acid and an alcohol react, with the elimination of water.

For every ester linkage formed in condensation polymerisation, one molecule of water is formed from the combination of a -H and an -OH group.

A polyamide is a polymer where the repeating units are bonded together by amide links

Polyester is a type of condensation polymer formed by the reaction between a dicarboxylic acid and a diol, with the elimination of water molecules.

A dicarboxylic acid is a carboxylic acid with two -COOH groups, one at each end of the molecule.

A diol is an alcohol with two -OH groups, one at each end of the molecule.

Condensation polymers can be identified because the monomers are linked by ester or amide links

X is an ester linkage.

A hydroxycarboxylic acid is a monomer containing both an alcohol –OH group and a carboxylic acid –COOH group.

The formula of an amide group is –CONH–.