Lesson 1: Spontaneity and Introduction to Entropy PDF

Activity No. 3.1 Mess it Up! Would it be possible for the pieces to naturally arrange themselves...

Activity No. 3.1 Mess it Up! Would it be possible for the pieces to naturally arrange themselves back into a sorted state when shaken? Activity No. 3.1 Mess it Up! Is it likely to return to the original order by random shuffling? Activity No. 3.1 Mess it Up! Is it possible to have a perfect sequence of all heads or all tails in one toss? LEARNING TARGETS ▪ I can define Spontaneity and Entropy ▪ I can differentiate spontaneous and non-spontaneous reactions ▪ I can describe the factors that affects entropy What is Spontaneity of Reaction? - The spontaneity of the process refers to how it occurs on its own without the help of any external factor. - The reverse of any spontaneous process is non spontaneous. - Spontaneity only tells us whether a reaction will occur or not. - It does not predict the rate of a process (how fast or slow it occurs) What is Spontaneity of Reaction? Spontaneous Process - type of process which DOES NOT need the application energy to take place - Generally, irreversible process Example: ✓ Flowing of water from a higher level to a lower level ✓ movement of the heart ✓ expansion and contraction of the lungs ✓ ripening of fruits ✓ dissolving of sugar in water What is Spontaneity of Reaction? Nonspontaneous Process - NEEDS the use of energy to make the process happens Example: ✓ flowing of water up to the tank requires pumping action ✓ crystallization of salt out of water ✓ reassembling of broken glass ✓ conversion of water to hydrogen gas and oxygen gas Formative Assessment Directions: Identify whether the following processes is spontaneous or not. 1. Electrical energy produced by battery 2. A spoon dipped in boiling water gets hot. 3. Wood burns to ash after being set to fire. 4. Formation of ice at ambient temperature 5. A ball rolls up a hill. Spontaneity VS Enthalpy According to the Thomsen-Berthelot principle, almost all EXOTHERMIC processes are SPONTANEOUS. Examples: ✓ Cup of hot coffee spontaneously cools if left exposed on the top of the table ✓ formation of moisture on the surface of a glass containing ice water Spontaneity VS Enthalpy ENDOTHERMIC processes can occur also SPONTANEOUSLY. Examples: ✓ ice melts spontaneously once the temperature is greater than 0oC ✓ decomposition of limestone, CaCO3 to Ca(s) and CO2(g) occurs spontaneously at high temperature Spontaneity VS Enthalpy These simply shows that ENTHALPY CHANGE, ∆H is not the sole criterion in determining spontaneity. What is Entropy? ENTROPY (S) - number of ways the energy of a system can be dispersed through the motion of its particles - measure of degree of disorderliness of a system or randomness - it is a state function which means, the value of it depends on the present state of the system and not on the manner by which the state was reached What is Entropy? What is Entropy? Factors that Influence Entropy TEMPERATURE ✓ as the temperature increases, entropy of the system increases due to the increased in average kinetic energy and the freedom of the particles in the system ✓ Third Law of Thermodynamics states that a perfectly ordered pure crystalline solid at zero Kelvin will have zero entropy Factors that Influence Entropy NUMBER OF PARTICLES ✓ chemical reactions that produce higher number of product particles than that of reactant particles are usually spontaneous ✓ increased in the number of particles lead to more disorder in the system and thus its increased entropy Factors that Influence Entropy PHASES ✓ The solid phase is the most ordered state and thus has the lowest entropy. ✓ The gaseous phase is the most disordered state and thus has the highest entropy ✓ S(gaseous) > S(liquid) > S(solid) Factors that Influence Entropy Factors that Influence Entropy The degree of disorderliness of a simple substance can generally be determined by the number of arrangements that the molecules can have in the system The higher the number of types of molecules, the higher the degree of disorder. Entropy being dependent on kinetic energy also tells us that at higher temperatures where KE is higher, entropy is also higher Make Connection! “Nature loves chaos” Can you give examples of situations in daily life where disorder naturally increases? Formative Assessment Directions: Predict the sign of the change in entropy for the following processes. 1. Formation of nitrosyl chloride (NOCl) from nitric oxide and chlorine gases 2NO(g) + Cl2(g) → 2NOCl(g) 2. Freezing of water 3. Heating liquid water to its boiling point