Simple molecular substances Flashcards
What does a simple molecule consist of?
a few atoms joined together by strong covalent bonds
What type of elements can simple molecular substances be (metals/non-metals)?
non metal elements
compounds of non metals
Describe the typical boiling/melting points
low
Describe the typical state at room temperature
gas or liquid
substances with large molecules (e.g. wax) are typically solids instead
Do simple molecular substances conduct electricity?
no; in solids, liquids and gases
however some conduct when dissolved (aqueous)
Explain the boiling points of simple molecular substances
low
the molecules are held together by weak intermolecular forces
when a molecules melts/boils the intermolecular forces are overcome
the covalent bonds don’t break
the forces are weak and so require little energy to break
What holds the molecules together?
weak intermolecular forces
Explain the typical states at room temperature
low melting/boiling points
the weak intermolecular forces between molecules are overcome in state changes
they require little force to break, so not much energy
this results in the weak forces already being broken at room temperature, causing a liquid/gas state
Why don’t they conduct electricity when solid, liquid, or gas?
- the molecules are not electrically charged
- the molecules do not contain spare electrons that are free to move
Why do some conduct when dissolved in liquid?
- break down into ions
- ions have a charge and are free to move around
- this causes the solution to conduct electricity
Explain the insolubility of some simple molecular substances
the intermolecular forces between water and the substances are weaker than those between:
- the water molecules
- molecules of the substance
Explain the solubility of some simple molecular substances
they dissolve if they can form strong enough intermolecular forces with water molecules
- hydrogen and oxygen are sparingly soluble
- CL, CO2, sulfur dioxide, ammonia, ethanol, sugar are all soluble
Describe the typical solubility of simple molecular substances
insoluble
Nitrogen is a colourless, unreactive gas at room temperature.
Explain why it is suitable for use an an insulator in high-voltage electrical transformers
nitrogen is unreactive
it will not react with materials used in the transformer
nitrogen can insulate the parts in the transformer as it does not conduct electricity
Ammonia, NH3, is a simple molecular substance.
Explain, in terms of intermolecular forces, why it is in the gas state at room temperature
weak intermolecular forces between ammonia molecules
they are easily overcome, and require little energy to break
