Keywords Which keywords might you use when describing

Keywords Which keywords might you use when describing each type of bond? S Electrostatic attraction Ionic bond Covalent bond Metallic bond Lattice Alloy Ionic Bonding t n t a i n G ale es v tur o C uc r t S im p M le ol co ec va ul le es nt Metallic Bonding

Which keywords might you use when describing each type of bond? Ionic Bonding Strong bonds Opposite charged ions Fixed position lattice Giant Covalent Structures Strong bonds All atoms Lattice No electrons/charges Simple covalent Molecules Strong bonds within molecule Weak intermolecular forces No charges Metallic Bonding Strong bonds Between ions Free electrons Layers

Answering an exam question…… Why is sodium chloride a solid at room temperature? Steps to success • What is the structure? • What type of bonding and forces are present? • Is the melting/boiling point high OR low? • How much ENERGY is needed to break the forces/bonds?

Answering an exam question…… Why is sodium chloride a solid at room temperature? Steps to success • Giant ionic lattice structure • Strong ionic bonds • High melting point because • Lots of energy is needed to break the strong ionic bonds

Exam question The boiling point of methanol is +65 °C; the boiling point of oxygen is – 183 °C. Methanol and oxygen each have an Mr value of 32. Explain, in terms of the intermolecular forces present in each case, why the boiling point of methanol is much higher than that of oxygen. (3) Steps to success • What intermolecular forces are there between the oxygen molecules? • What intermolecular forces are there between the methanol molecules? • Which is stronger?

Exam question The boiling point of methanol is +65 °C; the boiling point of oxygen is – 183 °C. Methanol and oxygen each have an Mr value of 32. Explain, in terms of the intermolecular forces present in each case, why the boiling point of methanol is much higher than that of oxygen. (3) Steps to success • van der Waals’ forces between oxygen molecules; 1 Hydrogen bonding between methanol molecules; 1 H-B stronger than van der Waals’ OR stronger IMF in methanol; 1 • (if dipole-dipole forces in O 2 or methanol, allow comparison, hence max 2) • (if ionic/covalent etc. max 1) • (mention of bond break = CE = 0)

Answering an exam question…… Why does potassium chloride conduct electricity when molten or in solution but not when solid? Steps to success • What is the structure? • Does it contain ions or delocalised electrons? • Are they in fixed positions or free to move? • Can something be changed so that the are free to move?

Answering an exam question…… Why does potassium chloride conduct electricity when molten or in solution but not when solid? • Giant ionic lattice structure • Contains ions • That are in a fixed position so they are not free to move so do not conduct electricity • When molten or dissolved in water they are free to move so conduct electricity