Properties of solids liquids and gases

What are ionic solids?

An ionic solid is made up of cations (positive ions) and anions (negative ions) held together by an electrostatic attraction between the oppositely charged ions

How are ions arranged in ionic solids?

• The ions in an ionic solid are arranged in a regular pattern of alternating positive and negative ions to give a solid crystal lattice

What is the electrostatic force dependent on?

• The strength of an ionic bond increases as the magnitude of the charges increase and as the ions get smaller and vice versa

What are the properties of ionic solids?

1. high melting points and high boiling points

2. poor conductors of electricity in solid state

3. Brittle

Why do ionic solids have high melting and boiling points?

• This is a result of the strong electrostatic attraction between the oppositely charged ions

Why can’t ionic solids conduct electricity?

• Ions are in a fixed position and cannot move freely

• However, ionic solids can conduct electricity in solution and molten state due to the presence of mobile ions

Why are ionic solids brittle?

As stress is applied, the ions slide and like ions are aligned together, this causes repulsion between the similar charged ions and the lattice breaks

What is a lattice?

 A regular repeating arrangement of particles 

What is lattice energy?

 The energy required to break the electrostatic force in a lattice

What is the shape of ionic compounds?

A crystalline

What are metallic solids?

• Metallic solids are made up of metal atoms held together by electrostatic forces of attraction between positive metal ions and delocalized electrons

What is the arrangement in metallic solids?

Metallic solids consist of a regular lattice of positive metal ions (cations) surrounded by a “sea” of delocalized (free) electrons. These electrons are not bound to any one atom; instead, they move freely throughout the structure.

What are the properties of metallic solids?

1. Good conductors of heat and electricity

2. High melting and boiling points

3. Malleable

4. Ductile

5. Lustrous (shiny)

Why do metallic solids have high melting and boiling points?

Due to the strong electrostatic force of attraction between the positive metal ions and the sea of delocalized valence electrons

Why can metallic solids conduct electricity?

Delocalized electrons carry charge

Why are metallic solids ductile and malleable?

This is due to the layers of positive ions being able to slide over each other

Why are metallic solids lustrous?

free electrons reflect light

what are alloys?

Alloys are mixtures of two or more elements, where at least one is a metal

Why are alloys made?

To make the material

• harder

• stronger

• lighter 

• more resistant to corrosion 

What are the 2 types of alloys?

• Substitutional alloys

• Interstitial alloys

What are substitutional alloys?

When atoms of one metal replace atoms of another metal in the metallic lattice because their atomic radiuses are similar and they have similar chemical-bonding characteristics

What are Interstitial alloys?

In interstitial alloys, small atoms of another element fit into the spaces (interstices) between the larger metal atoms in the metallic lattice — instead of replacing them, because they have smaller radii and different chemical-bonding characteristics

What are molecular solids?

Solids of non-metal that are not noble gases held together by intermolecular forces

What are the properties of molecular solids?

• non-conductors of electricity

• generally soft and brittle

• low melting points

what are covalent network solids?

Covalent network solids consist of atoms held together in large networks by covalent bonds

Why are covalent network solids harder and have a higher melting points than molecular solids?

because they contain covalent bonds which are stronger than intermolecular forces

What are some examples of covalent network solids?

Carbon allotropes:

• Graphite

• Graphene

• Diamond

• C60 (bucky ball or a buckminsterfullerene)

What is the geometric arrangement around each carbon in diamond?

Each carbon atom is surrounded by a tetrahedral arrangement of other carbon atoms to form a huge molecule

What is the hybridization of the carbon atoms in diamond?

sp³ hybridized

How are the carbon atoms held together in diamond?

They are held together by strong carbon-carbon single covalent bonds

How many covalent bonds does each carbon atom form with another carbon in diamond?

4

What are the bond angles in in diamond?

109.5 °

Is diamond large covalent or simple?

Large covalent lattice 

What are the physical properties of diamond?

• rigid and Hard (used as a cutting tool)

• high melting points

• poor conductors of electricity

• good conductors of heat

What is the geometric arrangement around each carbon in graphite?

carbon atoms are arranged in layers of six-membered (hexagonal) rings (Trigonal planar around each carbon atom)

What is the hybridization of the carbon atoms in graphite?

the carbon atoms are sp² hybridized and have one unhybridized 2p orbital

How are the carbon atoms held together in graphite?

They are held together by strong carbon-carbon single covalent bonds

How many covalent bonds does each carbon atom form with another carbon in graphite?

3

What are the bond angles in graphite?

120 °

Is graphite large covalent or simple?

Large

What are the physical properties of graphite?

• Good conductor of electricity

• Brittle

• Used as a lubricant (slippery)

• High melting point

• soft

Why is graphite Slippery?

• Weak IMF forces mean that the adjacent layers can slide past one another easily, an advantage in lubrication because the sliding layers allow for movement

Why is graphite brittle?

The brittle nature is because the layers of hexagonal carbon rings are held together by weak London dispersion forces

Why can graphite conduct electricity?

This is due to the delocalised electrons, that are able to move, in the unhybridized 2p orbital

What is silicon dioxide also known as?

Quartz or sand

What is the geometric arrangement in silicon dioxide

• Like diamond, it has a tetrahedral structure

• However, each silicon atom forms covalent bonds with four oxygen atoms while each oxygen atom forms covalent bonds with two silicon atoms

what are the physical properties of silicon dioxide?

• Hard

• high melting point

• poor conductor of electricity

What is the geometric arrangement of silicon carbide

• Silicon carbide has a tetrahedral crystalline structure consisting of four carbon atoms covalently bonded to a single silicon atom at the center

what are the physical properties of silicon carbide

• Insulator

• high melting point

• Hard (cutting tool)

• resistant to high temperature

why is silicon carbide hard?

• Like in diamond, the hardness of silicon carbide is derived from the tetrahedral structure of silicon and carbon atoms which are held together by strong covalent bonds

• This makes it useful as a cutting tool, bearings and mechanical seals

why is silicon carbide an insulator?

• This is because there are no free electrons which can act as mobile charge carriers

• But, it can exhibit the electrical properties of a semiconductor when impurities are added

why is silicon carbide resistant to high temperatures?

• Due to the strong silicon-carbon covalent bonds, silicon carbide has a low thermal expansion and high temperature resistivity

• This means that it is used in the manufacture of fire bricks and other heat-resistant materials

What are the 2 categories of solids?

• Crystalline

• Amorphous

What are Crystalline solids?

Solids in which atoms are arranged in an orderly repeating pattern called a crystal lattice

What are examples of crystalline solids?

• Ionic solids

• Molecular solids

• Covalent solids

• Metallic solids

What are amorphous solids?

Solids in which particles are arranged in a random, non-repeating pattern and have a disordered structure

What are example of amorphous solids?

• Glass 

• Plastic 

• Rubber

• Obsidian

Is the molar volume for solids and liquids of a particular substance the same?

Yes

What is molar volume?

Molar volume refers to the volume of one mole of a substance under standard conditions