Module 1: Kinetic Molecular Models of Liquids and Solids PDF

MODULE 1: KINETIC MOLECULAR MODELS OF LIQUIDS AND SOLID OBJECTIVES : At the end of the lesson, the students should be able to: 1.Use the kinetic molecular model to explain properties of liquids and solids. 2.Describe and differentiate the types of intermolecular forces. 3.Predict the intermolecular...

MODULE 1: KINETIC MOLECULAR MODELS OF LIQUIDS AND SOLID OBJECTIVES : At the end of the lesson, the students should be able to: 1.Use the kinetic molecular model to explain properties of liquids and solids. 2.Describe and differentiate the types of intermolecular forces. 3.Predict the intermolecular forces present in a molecule. 4.Describe the properties of liquids, and explain the effect of intermolecular forces on these properties. 5.Explain the properties of water based on its molecular structure and intermolecular forces. 6.Measure and explain the difference in the viscosity of some liquids. 7.tate the role and importance of intermolecular forces of attraction on the interactions in and between phases of matter. MODULE 1: KINETIC MOLECULAR MODEL The word Kinetic comes from the Greek word 'Kinein' which means to move. The speed of particles is proportional to the temperature of a substance.Increased temperature means particle move at a faster speed. The Phase at which any substance may exist depends Kinetic Molecular Model Kinetic relates to movement while molecular relates to particles. Kinetic Molecular Model of matters relates to matter as made up of particles that are constantly moving It has four premises: 1.All matter consists of particles 2.The particle are in constant random motion 3.There are spaces between the particles 4.There are forces of attraction and repulsion. TABLE 1.1: PARTICLE DESCRIPTION OF EACH PHASE OF MATTER CRITERION SOLID LIQUID GAS Freely moving, Molecular Closely packed Slightly far from very far from arrangements together one another one another Definite volume, Indefinite Definite volume assumes shape Volume/Shape volume and and shape of an occupied shape part of a container Density High High Low Motion of Vibration in place Random Fast random Molecules Kinetic Molecular Model When solids or liquids are heated up, the kinetic energy of their particles increases causing them to move faster. As temperature and kinetic energy rises there comes a time that the movement of the particles overcome the forces of attraction between each particles and they change phase. Solids can melt or sublime and liquids can vaporize.  Solidification or freezing ( liquid to solid ) Melting (solid to liquid ) Vaporization (Liquid to gas) sublimation(solid to gas) Intermolecular Forces refers to the attraction between atoms, molecules, and ions when they are placed closed to each other.They are much weaker than intramolecular forces which is the force that holds the atoms together within the molecule. It is also referred to as the van Der Waals forces. There are three types of intermolecular forces (from weakest to strongest): 1.London Dispersion Forces 2.Dipole-Dipole Interactions 3.Hydrogen Bonds London Dispersion Force Weakest of the intermolecular forces It exists to all types of substance whether they are ionic, covalent, polar or nonpolar. It occurs via instantaneous dipoles(temporary dipoles) The more electron a molecule has, the stronger the LDF.Example: Bromine,BR2 has more electrons than chlorine, Cl2 ,so Bromine has stronger LDF.Since stronger attraction means higher boiling point, Bromine has higher boiling point than chlorine.Doesn't require tons of energy to break. Dipole-Dipole Interactions Strongest type of intermolecular force of attraction Exists on molecules that are polar or have permanent dipole moment. Dipole moment occur when there is a separation of charge.It arises when there is differences in electronegativity which is the measure of the tendency of an atom to attract a bonding pair of electron. Dipole -Dipole Interactions Difference in electro negativity results in uneven sharing of electron resulting in one side of electron to be partially positive and the other side to be partially negative. Polarity in liquid also determines miscibility or the ability to mix without separation of phases.General idea is that polar liquids mixes with polar liquids but not with nonpolar liquids;hence, water (polar) does not mix with oil (nonpolar) Hydrogen Bonds Strongest type of Dipole-Dipole Interactions Interactions between hydrogen (H) and highly electronegative atoms (F,O,N): Hydrogen just want to have FON This type of interaction occurs in inorganic molecules such as water, and organic molecules such as DNA and proteins.