[CHEM] Chapter 2.1 - Kinetic Particle Theory

1 DARRELL ER (COPYRIGHTED) TOPIC 2.1: KINETIC PARTICLE THEORY DARRELL ER (COPYRIGHTED) ©

2 CHAPTER ANALYSIS THE ABOUT TIME EXAM WEIGHTAGE • Straight forward chapter • 2 key concepts • 1 advanced concepts • Usually tested in MCQs 🡪 2009 (2), 2010(1), 2011 (2), 2012 (1), 2014 (1), 2016 (1), 2017 (1) • Structured 🡪 2010 (6 marks) • Light overall weightage • Constitute to 2.5% of marks for past 5 year papers • Less commonly tested in recent years DARRELL ER (COPYRIGHTED) ©

3 BASICS MUST KNOW Solid Liquid Gas • Fixed volume • Fixed shape • Cannot be compressed • Does not flow • Fixed volume • No fixed shape • Cannot be compressed • Flows easily • No fixed volume • No fixed shape • Can be compressed easily • Flows in all direction DARRELL ER (COPYRIGHTED) ©

4 KINETIC PARTICLE THEORY OF MATTER MUST KNOW The theory states that: • all matter consist of particles that are too small to be directly visible, • the particles are always in a constant state of random motion at varying speeds. DARRELL ER (COPYRIGHTED) ©

Physical Properties Solid Liquid Gas Particulate model of matter Arrangement Closely packed in an orderly arrangement Loosely packed in a disorderly arrangement Far apart & random arrangement Forces of attraction Very strong attractive force Strong attractive force Weak attractive force Density Very high density High density Low density Movement Vibrate about its fixed position Particles sliding over one another freely Move about at high speeds randomly Energy Increasing energy 5 KINETIC PARTICLE THEORY OF MATTER KEY CONCEPT DARRELL ER (COPYRIGHTED) ©

6 CHANGE IN STATE DARRELL ER (COPYRIGHTED) ©

7 MELTING (SOLID TO LIQUID) • During melting, the particles gain energy from the surroundings and vibrate vigorously about their fixed positions until they have sufficient energy to overcome and break free from the attractive forces. • The temperature remains constant during the melting process as the heat energy absorbed is used to overcome the forces of attraction. • A mixture of solid and liquid is present during this stage. The temperature of the matter (solid) is a measure of the average kinetic energy the matter possesses. DARRELL ER (COPYRIGHTED) © Temperature / °C solid + liquid solid liquid Melting starts Melting point Melting ends Time/min

8 FREEZING (LIQUID TO SOLID) • At A, the particles have lost enough kinetic energy and freezing starts. • The particles after losing most of their kinetic energy, no longer have enough energy to overcome the forces of attraction between themselves and would return to their fixed position. • Between A and B, the freezing process is ongoing. The temperature remains constant because heat energy is being released to the surroundings. The release of heat energy negates the cooling effect resulting in the temperature remaining is