Chemisty - need help with a couple of dot points (1 Viewer)

[onesikgypo]

just to do with module 1 the points im having trouble summerising are:

describe molecules as particles which can move independently of each other

identify differences between physical and chemical properties of elements, compounds and mixtures

explain why the forumal for an ionic compound is an empirical formula

 

[Dreamerish*~]

describe molecules as particles which can move independently of each other

That explains itself.

identify differences between physical and chemical properties of elements, compounds and mixtures

Physical properties are those that can be easily reversed, such as boiling, melting and freezing; whereas chemical properties are those that cannot be (easily) reversed, such as boiling an egg, or hydrolysis of water.

In more technical terms, physical properties are related to the intermolecular forces (e.g. hydrogen bonding, disperson forces, dipole-dipole forces) between molecules, while chemical properties are related to the intramolecular forces (e.g. covalent bonds, metallic bonds, ionic bonds) within the molecules. For example, when boiling water, the water molecules spread away from each other as they become gaseous - they are still intact water molecules. However, during hydrolysis, the hydrogen atoms of water are separated from the oxygen atoms, breaking up the individual water molecules - this is a chemical reaction.

explain why the forumal for an ionic compound is an empirical formula

This is because ionic compounds do not form molecules. They are a continuous lattice of cations and anions bound together by their opposing charges. Only molecules (covalent molecular) have empirical formulae.