Holaaaaa, i dont know if you’ve been outside in the New England are but boy is it hot…. and the is coming from a girl that is from Jamaica…. well despite the sweltering heat overcoming my body in my room, we are going to learn some Chemistry cause why not.
So, usually when you’re speaking about some kind of change it usually relates to the system and the surrounds which together make the universe. Believe it or not this kind of relates to chemistry. So when we consider change, we think about what the system is doing. We also ask the question Is the entropy of the system increasing or decreasing? So you are probably like what the heck is this person saying but if i can get it you can. That question is like asking Is the rubber band producing heat energy or releasing heat energy when speaking to a stretched rubber band? System system system, there are two, closed or open. Open is a lot shorter than closed. So open is when the energy can pass between the system and the surroundings. This is just like when you want some tea and you but the kettle on the stove, it is an open system. Now closed system is a system that is isolated from the surroundings and heat can neither enter nor leave. Like chemistry its very hard to achieve (sh don’t tell my teacher that). So i was saying how hot today was which means that everyone had their water bottles. Believe it or not the water bottle was a closed system. that was all the stuff on spontaneity.
So now onto enthalpy changes. So when heat energy is released from the system, the surroundings gain that energy, while the system loses energy. So this is kind of like when you feel heat energy coming from the system which is really just whats really happening when you touch something and its hot. When a system loses heat energy, there is a loss in the amount of enthalpy that the system contains. The change of enthalpy is negative.
Now the opposite, when heat energy is absorbed by a system, the surrounding must hive that heat energy to the system. Like all things, the energy must come from somewhere. The Law of Conservation of energy stated that energy cannot be created or destroyed. It can only be transferred from one location to another. I know we all know this cause we literally learn this every year for the past 5 years. So since this is the flip of the other one, you feel heat energy leaving your hand and going to the system which is really just when your hands feel cold. You experience this a lot in those awfully cold winters where you are just permanently cold. When a system gains energy, there is an increase in the amount of energy the system possesses. The chant of enthalpy is positive.
Entropy changes a lot apparently. Whenever a change occurs, particles inside the system are rearranged. The new arrangement is either more or less disorganised. The new arrangement is either more or less disorganized. When the new arrangement is more disorganized the entropy has increased. The change in entropy is positive and the final entropy is a larger value than the initial entropy. On the flip side, when the new arrangement is less spread out or more organized, the entropy has decreased. The entropy change is negative and the finial entropy is a lower value than the initial entropy. When materials change from gas to liquid, or liquid to solid the entropy decreases.
Changes can occur either spontaneously or not. There are two factors that affect spontaneity: changes in enthalpy and changes in entropy. Exothermic changes drive a process toward spontaneity. This is because substances are produced that have lower energy than the reactants from which thy formed. Lower-energy states are favorable. Changes that result in an increase in entropy of the system also drive a process toward spontaneity. This is because nature tends to become more disorganized over time. If both factors change in the direction that favors spontaneity, the reaction will definitely be spontaneous. If neither factor changes in the direction that favors spontaneity, the reaction will definitely not be spontaneous. If only one change occurs in a favorable direction, the more dominant change will determine if the reaction is spontaneous. A third factor determines if a process will be spontaneous. Consider the freezing of water to form ice. If the water is left on the counter, freezing is not spontaneous. However, if the water is placed in the freezer. the process becomes spontaneous. The temperature at which a process occurs can affect whether or not a process will be spontaneous. The Gibbs free energy is a measurement that can be used to tell whether a change will occur spontaneously. If the change in Gibbs free energy is negative, the change will occur spontaneously at the given temp.
If you don’t know anything, know this the equations for the change in Gibbs free energy:
ΔG= ΔH – TΔS (kelvins)
ΔH=negative ΔS=positiver then ΔG will be negative
ΔH = positive ΔS=negative then ΔG will be positive
ΔH & ΔS = same sign then ΔG could be both
So i dont know if you guys remember but in the fall we spoke about polymers. Well they are back to haunt you. I’m joking it should be so bad cause you’ve learnt it already…. i hope. So polymers are simply molecules made of long strings of monomers that are attached to each other. This whole idea makes materials made of polymers be unusual. I have two brothers and when i was younger rubber bands were a big thing, you know to sting them and all. Well when i was trying to stretch it and string my brother the entropy i slow because the molecules are pulled relatively straight and lined up. Another reason is because the aligned molecules are able to experience attractions to each other. Molecules exhibit a similar relationship between distance and energy. Molecules experience relatively weak attractions for each other when they are close together. This really just means when a molecule is attracted to another it is at a lower energy state.
When the rubber band is in a contracted state, the entropy is high because the molecules are tangled around each other. This is also because the molecules are father apart from other molecules. When a molecule does not have others nearby molecules to be attracted to, the molecule is at a higher energy. Just think when people don’t have friends around their is more energy cause they are looking for people. Nature favours changes that result in lower energy. Therefore the enthalpy factor would favour the rubber ban becoming stretched. The entropy factor would favour the contracted state.
So like everything in science, temperature has an effect on rubber bands. The rubber band stretched when you decreased its temperature by cooling it with cie. This means that at a lower temperature, the stretched state is favoured. The change in enthalpy drives the rubber band towards a stretched state. Therefore at a lower temp the entalpu factor becomes dominant over the entropy factor. Because the rubber band is stretched when cooled with ice and is contracted at room temp, increasing temp causes the rubber band to contract. As the temp increases the change in entropy makes the contraction of the rubber band more and more spontaneous. Therefore, the rubber band contracts more than it does at room temp.
Now back to your favourite, this one feels like its all over the place cause we are back with polymers. Polymers are the most adaptable substances that technology had produced. Their properties are changeable which is kinda cool and for me to say that means it is actually cool cause come one we are seeking about chemistry. The coolest thing that polymers are used for in medicine. I am sure you all watch Grey’s Anatomy and know Christina Yang, the cardiothoracic surgeon. In a;most all episodes she would put a heart valve in well this one of the ways polymers are used in medicine. I know this is kind of off topic but tonight is the season finale of Greys and I’m kinda freaking out cause last week was so good and they can do so many things with this episode. Okay back to chem. So when Yang goes in, she uses a polymer called thermoplastic polymer which is used to stitch the working parts of the mechanical heart to the heart itself. Thermoplastics are usually polyesters or polymers in which the repeating monomer forms an ester linkage between an organic aid and an alcohol. Polyethylene terephthalate is a copolymer of terephthalic acid and ethylene glycol connected by the ester functional group.
Properties of polymers are such that they can be so sturdy that they can be used to construct cars and buildings, or so elastic that they can be used to make trampolines and playground balls. The fields of polymer chemistry and materials science are exciting and employ many chemists.
Well this was the last time you will see me writing so i guess i should let you in on a little secret,
So you know i started with the line Hey everyone todays a good day to learn chemistry i actually stole that from Greys.
Derek Shephard said that before all of his surgeries.
Thank you so much for a Great year Mr. C and actually making me understand Chemistry!!!