Properties Of Substances

What are the three states of matter?

Solid, liquid and gas.

What takes place at the melting point?

Melting and freezing.

What takes place at the boiling point?

Boiling and condensing.

What does the amount of energy needed to change state depend on?

The strength of the forces between the particles of the substance.

What does the nature of the particles involved depend on?

The type of bonding and the structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance.

What are the limitations of the particle model of matter?

In the model there are no forces, that all particles are represented as spheres and that the spheres are solid.

In chemical equations, what are the three states of matter are shown as?

(s), (l) and (g), with (aq) for aqueous solutions.

What is the structure of ionic compounds?

What are the properties of ionic compounds?

These compounds have high melting points and high boiling points because of the large amounts of energy needed to break the many strong bonds. When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.

What is the structure of small molecules?

They have weak (intermolecular) forces between the molecules. These weak forces are overcome when they change state not the strong covalent bonds.

The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.

What are the properties of small molecules?

Low melting and boiling points as small amounts of energy is needed to break the intermolecular forces and they do not conduct electricity as particles do not have an overall electric charge.

What are polymers an example of?

A covalently bonded substance with very large molecules.

What are the properties of substances that consist of giant covalent structures?

They are solids with very high melting points. All of the atoms in these structures are linked to other atoms by strong covalent bonds. These bonds must be overcome for a change in state.

What are some examples of giant covalent structures?

Diamond, graphite and silicon dioxide.

What is the structure of metals?

Metals have giant structures of atoms with strong metallic bonding meaning most metals have high melting and boiling points.

How are the atoms arranged in pure metals?

Atoms are arranged in layers, which allows metals to be bent and shaped. Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder.

What is an alloy?

A metal mixed with other elements.

Why are alloys harder than pure metals?

The different sized atoms of the metals distort the layers in the structure, making it more difficult for them to slide over each other, and so make the alloys harder than pure metals.

Why are metals good conductors of electricity?

The delocalised electrons in the metal carry electrical charge through the metal.

Why are metals good conductors of thermal energy?

Energy is transferred by the delocalised electrons.