10.5 The Solid State of Matter

• CO2 is a supercritical fluid with properties of both gas and liquid.
• It works like a liquid and deep into the coffee beans.
• Coffee's flavor and aroma compounds are intact despite the removal of 97- 99% of the caffeine.
• The removal of CO2 from the coffee beans is easy because it is a gas under standard conditions.
• The caffeine recovered from coffee beans can be used as an ingredient in other foods or drugs.

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• The entities of a solid phase can be arranged randomly or in a regular pattern.

• Crystalline solids are formed by metals and ionic compounds.
• A mixture of large molecules or a mixture of molecules whose movements are more restricted are called a large molecule or a mixture of large molecule.
• Candle waxes are made from large hydrocarbons.
• Depending on the conditions under which it is produced, some substances, such as boron oxide, can form eithercrystalline or amorphous.
• A transition to the crystalline state can be made with appropriate conditions.

• Crystalline solids are classified according to the nature of the forces that hold them together.
• The bulk solids have physical properties that are mostly responsible for these forces.
• The following sections give descriptions of the major types.

• There are many ionic crystals with high melting points.

• Liquids and Solids between full charges are larger than those between partial charges.
• In a later discussion of lattice energies, this will be looked at in more detail.
• When molten or dissolved, ion particles do conduct electricity because they are free to move.
• Ionic compounds are formed by the reaction of a metallic element with a nonmetallic element.

• An ionic solid is sodium chloride.

• They do not shatter because of their malleability, which makes them useful construction materials.
• There are different melting points of metals.
• Mercury is a liquid at room temperature.

• Several post-transition metals have low melting points.
• The strengths of metallic bonding among the metals are reflected in these differences.

• A metallic solid is copper.

• Many minerals have bonds.
• To break or melt a covalent network solid, bonds must be broken.
• Hardness, strength, and high melting points are some of the characteristics of covalent network solids.
• One of the hardest substances to melt is diamond.

• A three-dimensional network of bonds is shown in the structures of diamond, Silicon dioxide, and Silicon carbide.
• There are sheets of covalent crystals that are held together in layers by noncovalent forces.
• Graphene is soft and electrical.

• The melting points of the crystals show the strengths and weaknesses of the attractive forces.
• Small symmetrical molecules, such as H2, N2, O2, and F2, have weak attractive forces and form very low melting points.
• Substances made of larger, nonpolar molecules have larger attractive forces and melt at higher temperatures.

• At higher temperatures, the molecules with permanent dipole moments melt.
• Ice and table sugar can be examples.

• The melting point of carbon dioxide is -78 degC.
• Iodine is a non-polar molecule that forms a solid at 114 degrees.

• The same forces or energy hold the atoms of the same type in the same place, so a crystall solid has a precise melting temperature.
• The crystal in Chapter 10 requires the same amount of energy to be broken as the Liquids and Solids attractions.
• When a material is heated, the weakest intermolecular attractions break first.
• The stronger attractions are broken as the temperature increases.
• Over time, the materials become softer over a range of temperatures.

• Our world is made of carbon.
• The existence of carbon-based life forms is possible because of the unique properties of carbon atoms.
• One of the hardest-known substances is diamond, which is soft enough to be used as pencil lead.
• The carbon atoms in the different allotropes have different properties.

• Carbon atoms bonding in all directions is what makes diamond very hard.
• The weak attractions between the carbon layers cause the pencil lead to rub off on the paper.
• The image shows the distance between the centers of carbon atoms.

• You might not be aware of a recently discovered form of carbon: Graphene.
• In 2004, Graphene was isolated by using tape to peel off thinner and thinner layers.
• It is a single sheet of material.
• Graphene is an excellent conductor of heat and electricity.
• These properties are useful in a wide range of applications, such as vastly improved computer chips and circuits, better batteries and solar cells, and stronger and lighter structural materials.
• The 2010 Nobel Prize in physics was awarded to two physicists for their work with Graphene.

• Buckyballs, nanotubes, and stacked layers can be formed from graphene sheets.

• The atoms, ion, and molecule are arranged in a pattern, but occasionally there are defects in the pattern.
• When the cations, anions, or molecule of the impurity are too large to fit into the regular positions, other distortions are found.
• Silicon crystals are doped with varying amounts of different elements to yield suitable electrical properties for their use in the manufacture of computer chips.