Unit 11: States of Matter

-- ++ Types of Covalent Bonds Polar Covalent Bond Polar Covalent Bond –e - are shared unequally –asymmetrical e - density –results in partial charges (dipole)

Nonpolar Covalent Bond Nonpolar Covalent Bond –e - are shared equally –symmetrical e - density –usually identical atoms Types of Covalent Bonds

If ΔEN is: Bond type is: < 0.4 Nonpolar covalent 0.4 < Δ EN < < Δ EN < 1.7 Polar covalent > 1.7 Ionic Given: Electronegativities of these elements H = 2.2C = 2.55N = 3.04O = 3.44F = 3.98 Na = 0.93K = 0.82P = 2.19S = 2.58Cl = 3.16 Determine bond type for the following bonds: H – H__________H – O ___________ H – C__________Na – Cl ___________ Take the absolute value of the difference!

Intermolecular Forces (IMF) Attractive forces between molecules. Attractive forces between molecules. Much weaker than Much weaker than chemical bonds within molecules (INTRAmolecular forces. within molecules (INTRAmolecular forces.

London Dispersion Forces London dispersion forces London dispersion forces –Exist in all atoms and molecules –Electrons within atoms are constantly moving around. Sometimes they are not disbursed evenly around the nucleus. –When atoms are close to each other, they are attracted due to the temporary area of partial + and - charges (temporary dipoles) produced.

London Dispersion Forces

Dipole-Dipole Forces -Attraction between two PERMANENT dipoles -Polar molecules ONLY. -Medium strength -Stronger when molecules are closer together

Types of IMF Types of IMF Dipole-Dipole Forces Dipole-Dipole Forces + + - - View animation online.animation

Hydrogen Bonding –Special kind of dipole-dipole –Occurs between molecules that have an H bonded to either O, N, or F. –Strongest –Not chemical bonding

Hydrogen Bonding Animation of water molecules being attracted to each other.

IMF and Boiling Point The stronger the IMF, the higher the boiling point. The stronger the IMF, the higher the boiling point. Molecule IMF (s) present Molar Mass (g/mol) Boiling Point ( o C) CH HCl H2OH2OH2OH2O London Disp. Dipole-Dipole London Disp./Dipole- Dipole/Hydrogen Bonding

Density

Compressibility The more empty space between particles, the easier it is to compress it. Solids are not easily compressed, liquids a little bit, gases a lot.

Liquid Properties Viscosity Viscosity –Resistance to flow Viscosity Demo Water Oil

Liquid Properties Surface Tension Surface Tension –attractive force between particles in a liquid that minimizes surface area. Creates a SURFACE that keeps the liquid together.

Detergents/Soap Oils don’t mix with water. Oils don’t mix with water. –Fats/oils are non polar –Water is polar –LIKE DISSOLVES LIKE Soaps and detergents disrupt the hydrogen bonding between the water molecules. Soaps and detergents disrupt the hydrogen bonding between the water molecules. A micelle is formed. (Detergent wraps around grease particle and it can be mixed with water.) A micelle is formed. (Detergent wraps around grease particle and it can be mixed with water.)

Cohesion and Adhesion Cohesion is the force of attraction between identical molecules in a liquid (cohesion is a result of intermolecular forces). Cohesion is the force of attraction between identical molecules in a liquid (cohesion is a result of intermolecular forces). Adhesion is the force of attraction between liquid molecules and a solid that is touching them. Adhesion is the force of attraction between liquid molecules and a solid that is touching them.

Liquid Properties watermercury Meniscus of water in a glass tube is concave: adhesion > cohesion Meniscus of Hg in a glass tube is convex: cohesion > adhesion

PROPERTIES OF SOLIDS Density: Solids are denser than their liquid form. Density: Solids are denser than their liquid form. –EXCEPT: wax, cork, ice  In these solids, the molecules are spaced farther apart than in their liquid form so they float. Ice corkwax

Crystalline vs. Amorphous: A crystalline solid has particles which are arranged in an orderly, geometric, 3-D structure. A crystalline solid has particles which are arranged in an orderly, geometric, 3-D structure. – Examples: sodium chloride, ice, gems and minerals

Types of Solids Amorphous (SiO 2 - glass) In an amorphous solid, the particles are not arranged in any particular pattern. Examples: rubber, plastics.

Phase Changes Temperature E. Q=mCΔT D. Q= mH v T b  B. Q =mH f C. Q=mCΔT T m  A. Q= mCΔT Thermal Energy (Heat)

Thermal Energy (heat) Phase Changes: Phase Changes: –B and D represent phase changes –Occur at constant temperature Temperature Changes Temperature Changes –A,C, and E –Temp is changing –Sloping portion of the graph

Thermal Energy (heat ) What is happening at each part of the graph: What is happening at each part of the graph: A. Substance is a solid. Can heat it up or cool it down along this line. A. Substance is a solid. Can heat it up or cool it down along this line. B. Phase change: solid-liquid. The temperature at B (Tm) is the melting (freezing) point. B. Phase change: solid-liquid. The temperature at B (Tm) is the melting (freezing) point. C. Substance is a liquid. Can heat it up or cool it down along this line. C. Substance is a liquid. Can heat it up or cool it down along this line. D. Phase change: liquid-gas. The temperature at D (Tb) is the boiling (condensation) point. D. Phase change: liquid-gas. The temperature at D (Tb) is the boiling (condensation) point. E. Substance is a gas. Can heat it up or cool it down along this line. E. Substance is a gas. Can heat it up or cool it down along this line.

Heat Calculations Q = m c ∆ T Q = m c ∆ T –Q = heat or thermal energy in Joules (J) or calories (cal) –m= mass in grams (g) –C = specific heat in J/(g o C) or cal/(g o C) –∆T= change in temperature in oC

Heat Calculations Q =mH f Q =mH f –Q = heat or thermal energy in Joules (J) or calories (cal) –m= mass in grams (g) –H f = Heat of fusion (J/g or cal/g); use for liquid- solid phase change

Heat Calculations Q =mH v Q =mH v –Q = heat or thermal energy in Joules (J) or calories (cal) –m= mass in grams (g) –Hv = Heat of vaporization (J/g or cal/g); use for gas-liquid phase change

Things to remember You can move from left to right or right to left along the curve. You can move from left to right or right to left along the curve. If you move left to right: If you move left to right: – all the processes are endothermic (heat must be supplied). –Your answer for heat calculations will be positive.

Things to remember If you move right to left: If you move right to left: – all the processes are exothermic (heat is removed/released). – Your answer for heat calculations will be negative. You have to write in the negative, but you solve the problem the same way!