Tayla'a Chem Blog

Just another Suffield Academy Blogs site

Entropy and Enthalpy: Changes in Rubber Bands

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!!!

Enthalpy: Exothermic and Endothermic Reactions

It’s a beautiful day to be alive and an even better day to learn some chemistry!!! 

I just looked at this chem talk and saw that it was 5 pages… which is quite long. I didn’t have solo today and i am giving up my nap for a chem talk so you better learn something. 

In the lab there were three concepts; spontaneous, thermodynamics and kinetics. Basically spontaneous  the change that continues without an input of energy. Thermodynamic is the study of how heat and other forms of energy are involved in chemical and physical reactions. Lastly, kinetics is the study of reaction rates and how they can be affected by variables such as concentration, particle size and temperature. Factos that change spontaneity is if the changes give off heat energy or absorb heat energy and if the change results in particles becoming more disordered or less disordered. Light bulb, you need to know that lower energies are more stable than higher energies. Just think when you jump you fall back to the ground, so energy changes in chemical reactions tend to happen in ways that allow the substances to end up with lower energy. Like most things in the world everything gets more disorganised over the course of time. IM sure your room was impeccably neat over fall term but now not that much. Well the same thing happens in chemistry. The changes in the which particles become disordered are favoured over those that make particles become more ordered.  IF one factor is favourable and the other is not, the stronger one controls whether the change is spontaneous. Im sure you could of predicted that because think in tug of war, the stronger side controls the game. IN our lab we were dealing with spontaneous reactions. The temperature went up when the substance went from a higher energy to a lower one. SO really this just means that at leas one of the facts affecting spontaneity is favourable for this reactions. 

I know i know this is one is kind of draining but if you were there when we were doing the lab it wasn’t that bad because you got to look at all the bubbles go up which was cool for about 10 seconds of the 5 mins.

Okay so when we did the magnesium and water mix stuff happened:

  1. bonds broke (requires energy so endothermic), new bonds form . To remember this think if you are in a relationship and drama starts friendships break which requires speaking which is the energy and then you make new friends. This may sound like I’m crazy but i bet you never forget it
  2. Forming bonds relaease energy (Exothermic change). For this one think when you make your new friends you can relieve all the stress you felt when fighting
  3. The overall net change can be endo or exo depending on whether the total energy input or the total energy output is greater. This one is the best so when your friendship ends it can either be on good terms or bad. BOOM Chemistry was just put into our daily teenage lives

So like all things, to show something you can draw it and enthalpy is no exception. Enthalpy can be drawn in an energy diagram. Have you ever walked pass a physics classroom and see the typical drawn graph. I know you know what im talking about well  this is kinda of energy diagram looks like. the only difference is this one shows the progress of the reaction from reactants to products along the horizontal axis. On the vertical axis the diagram shows the change in potential energy that occurs as substances progresss from reactant to product. I have a joke, so in them today we were learning this and the diagram was on the board but on the y axis he had NRG. So I’m sitting there really trying to figure out what that could possibly mean. So smart Tayla asks and i felt so dumb…. it mean energy. It was kind of funny though. Anyways back to chem, So these diagrams show two things: endothermic or exothermic and activation energy. So in the first one: the location of the reactant energy and product energy show whether the overall enthalpy change is endothermic or exothermic. If the starting point is higher than the end point then the system releases heat energy to surroundings and the overall enthalpy change is positive. Now the second thing is not affected by where its endo or exo (sorry but that is just too long to type so I’m going to stick with this :)). Bonds must always be broken  in the reactant before new bonds can be formed in products. This means that some initial energy must be supplies to the system in order for the reaction to begin. It is really just the bump in the curve to get from reactants to products. Also it is always positive. The intermediate state between reactants and products at the top of the barrier is called the activated complex. 

Related image Incase you have no clue what I’m saying

In our lab we had 4 test tubes

  1. Mg with water
  2. Mg , NaCl and water
  3. Granulated Mg and water
  4. Large piece of Mg and water

The first two were very slow with little heat and some bubbles of hydrogen. The last two was the same thing in different forms. I am sure if you had to bet which was faster you would guess the large [iece of Mg and would of been wrong :). the granulated was much faster because reactions can take place only when the reactants collide.  This is because when  the reactant is a solid these collisions can only occur on the surface. MORE SA = FASTER REACTION

The iron was a catalyst. so when writing the equation the Fe would go above the arrow. You’re probably like what the heck is a catalyst. I actually know this from last year cause i did bio which was my favourite subject. A catalyst is a substance that speed up a chemical reaction without being used by itself. It works by providing a lower energy alternative pathway for the reaction to take. Because of this more starting materials at a given temperature has enough energy to get over the energy barrier. This speeds up the reaction and generates hear quicker. As the temperature increases the reactions speeds up more. I know you’re impressed I knew that. 

Iron can’t get all the glory cause sodium chloride also plays a role in the reaction by being an electrolyte. When dissolved in water the salt provides a pathway for the electrons to move form the magnesium which is thus oxidised to the hydrogen atoms that are reduced. The oxygen in water remains in the same oxidation state as it beomes a part of the hydroxide ion. 

Now release that breath cause guess what it is all DONE. this first was kinda painful but in the end i kind of got into it which is shocking cause it is that ‘AMAZING’ thing called chemistry.

I feel like a rockstar so I’m gonna end with. 

Its been a great night now good night (crowd rages)

 

Chem To Go Page

  1. Only the 0.1 M of ZN (NO3)2 was conductive. I knew this because it was the only solution that made the LED light up. 
  2. I think d because it has an ion in it which is the key element to conducting electricity.
  3. a. Tap water is conductive resulting in it having the ability to electrocute you                                                                                                                                                                                                                                       b.It would be unsafe to take a bath in distilled water because the left over tap water may still conduct electricity.
  4. a. I think the sport drink                                                                                                                                                                                                                                      b. Putting the different sport drink ions in different beakers is what you would have to do 
  5. The control variable should be a part of the mix in both sides, while also conducting electricity.
  6. a. No voltage: No connection to transfer electrons to and from                                                                                                                                                                                                                                               b. No voltage: distilled water can’t conduct electricity                                                                                                                                                                 c. No voltage: to get a complete circuit the anode would have to be connected to the voltometer                                                                                                                                                                                 d. Decrease in voltage: the tin would consistently disintegrate 
  7. d
  8. c
  9. c

 

 

Solutions that conduct Electricity

It was a pretty gross day outside today. Rain rain and more rain is all i can say pretty much.

Despite the yuck outside chemistry is here to make your day better.

Did you ever think a solution that is water mixed with something could make electricity? I know i didn’t but boy was i proven wrong. This happened because of this insane thing called an electrolyte which is simply a substance that dissolves in water to make solutions that conduct electricity.  This happens because the solutions contains charged particles that are able to move. Without this there would be no conduction of electricity. Some compounds dissolve in water to form charged particles called ions. These compounds are usually made of positively charged metal ion and negatively charged metal ion to balance the charge. Remember when you were younger and tried to out 2 AA batteries in something and had to make sure the positive and negative were on the same side it is the same thing here except you actually know whats happening. A typical example is table salt. I actually just needed some of this because i just ate the blended popcorn in life but anyways.SO sodium chloride i just the fancy name for table salt. It is made of sodium ions (na +1) with charges of +1 and chloride ions (CL-) with charges of -1. When NaCl crystals dissolve in water, sodium ions and chloride ions separate form the crystals and are surround by water molecules. So now go back to your checklist, Are ions surrounded by water? Yes, Can the ions move about? Yes, Are they charges particles? Yes. everything was yes which means that sodium chloride is able to conduct electricity.

Molar compounds do not break up into ions when they dissolve. Simple meaning thet sugar remains as sugar molecules when it dissolves. Since molecules do not form charges particles in solution, solutions made of molecules dissolves in water do not conduct electricity. Molecules that do not form ions in solutions are called non-Electrolytes. 

So electrolytes conduct electricity a way to remember this is by electrolytes make you feel bettie when you’re sick and give you “electricity” to walk again

the  path of electricity in a Battery

This seems like something my dad would like. At home we call him Chuck like the guy in that adam sandler movie who can do everything cause it amazes me how much he can do everything and figure everything out. A bater has two half cells. The half cell where oxidation takes place is called the anode. the other half cell where reduction takes place is called the cathode. So the word half is used because one can’t exist without the other. So by now you should know that when every you say oxidation, reduction is not far away. well ding ding there is definitely a reduction and oxidation reaction occurring. In the lab we did, Electrons were produced by the oxidation of zinc metal at the anode. ZN -> Zn^2+ + 2e-

While the bater is operating the zinc metal electrode is slowly undergoing a reaction. Neutral zinc metal atoms make two products according to the equation. Zin ions and electrons are produced at the anode

The zinc ions enter the zinc nitrate solutions while the electrons travel through the wire. Eventually the electrons read the copper metal electrode where reduction takes place. When electrons read the copper cathode, they enter the reaction hall reaction: Cu^2+ + 2 e- -> Cu

SO in the half reaction, neutral copper metal atoms are made from copper ions from the solution combing with electrons. The copper metal electrode increases in mass because copper metal is slowly attaching to it. This was why a reddish sludge was produced.

Copper ions are not the only ions present. We started with Cu(NO3)2. It dissolved and split into Cu2+ and NO3- ions still surrounded by water molecules. As the positively charged copper ion n the solution gets used up, negatively charged nitrate ion gets pushed out the region because the solution must remain neutral. The only place for the NO3- ions to go is through the salt bridge. after passing through the bridge they enter the zinc half cell. The Zn2+ ions are being created at the anode as the batter operates. tThere is a need for additional negative ions to balance the increasing positive charge from the zinc ions.  

How doe this relate to the metal activity series. 

In a battery electricity only runs in one directions. Why well simply because of the relative activities of the two metal electrodes used in the half reactions. In this case the half reactions were converting from Zn metal to Zn 2+ ions in one of the cells and from Cu2+ to Cu metal atoms int he other cell. Zinc metal is more reactive than Copper metal. Therefore Zn will react spontaneously with Cu 2+ and Cu will not react spontaneously with Zn 2+. 

 

This lab wasn’t as fun as the last one with the colours but i guess you can say it wasn’t that bad because it was repeated material we have learned already.

 

How is light produced?

beautiful day to learn chemistry

It’s kind of funny that today of all days is when I’m writing this blog. Today was full of colour, i went painting for leadership and i ended up being the canvas… literally.

So i must of giving you a hint as to what today is, light and colours and prettiness. 

Firstly, light is a form of energy known as electromagnetic radiation: including X-rays, ultraviolet rays, microwaves and radio waves and visible light. Visible light is a special one because you eyes can detect it. So, i used a fancy word for light but how is it characterised? Thats simple, by wavelengths and its energy. I remember learning this is that awful thing called physics which shockingly helps and makes this topic in chem that much easier.  A wavelength of light is the distance between two corresponding points. Have you ever been in art class and they say draw the ocean so you just draw a swirly ling horizontally well. The highest point is the crest and the lowest point is the trough and from crest to crest or trough to trough is a wavelength. The wavelength is measure in nano metres (nm) which is one billionth of a meter. wow that is really really really small i think.

unlike in a race where everyone runs at different speeds, all waves of light travel at the same speed in a vacuum. This speed is called the speed of light. Air slows down light waves only a little, which makes sense because in a race the wind can slow you down if its very windy. Its fair to say that even in air all light waves travel at the same speed. 

So another property of light is frequency which can gee related to wavelength. 

speed of light 3 x 10^8 m/s = wavelength in metres x frequency in waves per seconds

c= lama x f

when doing an equation ensure you are consistent with units, so convert wavelength nanometers to meters

So usually when dealing with wavelengths the long ones have low frequencies and the shot ones have high frequencies. this idea is expressed as, “frequency and wavelength are inversely related, meaning that as wavelength increases, frequency decreases. 

Image result for electromagnetic spectrum

 

This picture pretty much shows everything I’ve been saying so if you’re like me and have to see things i got you

THe mathematic expression that that relates the two is

Energy measure in joules = planck’s constant: 6.63 x 10^-34 js x frequency s^-1

e = h x f

Light that has a long wavelength has less energy than light that has a short wavelength. The wavelengths go visible light range from 700 nm for red to 400 nm for violet. As the wavelength of light becomes shorter the energy of light increases. So imagine a rainbow, the red streak is the longest and violet is the shortest so you can just apply that same concept to wave lengths Res light has less energy than blue light and that is why red had no effect on the glow in the dark star. the wavelength of light determines if the light has enough energy to interact with the electrons in an atom. 

How does an atom produce light??

So we al know:that atoms are made of protons neutrons and electrons,protons and neutrons are located in the nucleus of the atom, the electrons exist outside the nucleus in certain allowable started that are called energy levels and the electrons in the outermost shell are called valence electrons. In Spectroscopy the idea is that energy is conserved. When an electron absorbs energy it van move from a lower energy level to a higher one. however the energy that the electron absorbs must be equal to the energy difference between the two levels. so your probably like what the heck is this person saying well think about this if you are walking up stair and don’t give you foot enough energy to go from stair to the next is it going to make it? no exactly so its just like the electrons, if it doesn’t get enough energy it will not be promoted to a higher energy level.  So in the lab red didn’t glow thats because it did not have enough energy to have any effect on the glow in the dark tape. 

when i was saying high and lower I’m sure you were jumping out of your chair to know the names. The higher one is the excited state and lower one is the ground state. The energy that an electron absorbs come from many different sources: heat energy, collision between particles in the material, chemical reactions visible lighter other forms of electromagnetic radiation. The electron however cannot remain in the excited state forever. it eventually falls to a lower energy state and gives up energy in the process. 

Fluorescence and Phosphorescence

Fluorescence is a common process by which light is emitted from atoms or molecules. 

Image result for Fluorescence  shows the process of fluorescence 

Phosphorescence when the glow in the dark tape gave an effect. IN this process there is another excited state in between where the electron is first promoted and the ground state. Depending on the conditions the electrons can get stuck i this state. As a result of this, the result of light in some cases of Phosphorescence is delayed over a period of time ranging from seconds to minds. This is why when you have a glow in the dark still that you crack it doesn’t automatically light up it takes time and when it is dying it doest instantly die but rather takes time, The elated emission of light causes the glow in the dark start to continue to glow long after the source of excitation is removed. In the lab we did a glow in the dark tape was irradiated with red orange, green, blue, UV and white light. Red, orange, yellow and green light did not do anything to the star because they did not have enough energy to move electrons from their ground state to an excited state. When the blue and ultra violet was used electrons are excited and the tape emitted a green yellow light. The white led also caused the tape to glow because a small portion of the light that the white led emits is in the blue portion of the visible spectrum. I don’t know why but i see this as a huge game where electrons are constantly trying to get energy so they can become happy (excited state) 

 

 

Redox Reactions

Hello World,

Today is the day, I have the feeling, Chemistry will finally be easy today and we will actually understand and not just pretend to. WE GOT THIS!!

So, today we go back to redox reactions. I dont know if you remember but we have touched on this before in about maybe November? 

So the first thing we have to fully understand is what is a metal? You’re probably thinking i obviously know that but do you really? So Metals are for one shiny, but they also have other important properties. One of the most important being the fact that they conduct electricity allowing them to be able to be used in electrical circuits. Im sure you know this one, but they conduct heat and where is on the most important places you need heat, none other than cookware. Metals are kind of like superheroes because they can withstand such high temperatures so they are able to build strong structures to help the people of the world. Another reason they remind me of superhero is because of its ability to shape-shift like avatar, turing into nails, hammers, flat surfaces etc. So you may be wondering how exactly do i identify metals on a periodic table, well you just draw a diagonal line from B to AT, everything to the right is a metal with the exception of H.

Medical times actually taught chemists a lot and now they are able to draw the conclusion of when an atom interacts with another only the arrangement of electrons is changed. From trying and experimenting, alchemists (Old time chemists) were able to discover thasome metals react more easily with most metal ion solutions than other metals do. Chemists were kind of like Special Agent Detecives because they had to look into every case to figures something else out. Due to this, Chemists made ways to measure numbers and figure out where a metal belongs in the activity series. This is all because of the Special Agent Chemists. 

So like in every subject, theres always special cases. In chemistry their are special reactions between metals and metals ions that help to make people understand. The reactions that occur between neutral metal atoms and metal ions are in a special class called Redox. The ‘OX’ in the word stands for oxidisation and is defined by giving up electrons.  The ‘RED’ stands for reduction which is receiving electrons and is simply and oxidisation equations backwards.

Eg.  zinc metal oxidises: Zn -> Zn ^2+  +  2e^-

Eg. copper ions reduce: Cu^2+  +  2e^- -> Cu

These both occur at the same time. Electrons that are given up have to be received by something. SO oxidation changes and reduction changes are often called HALF-REACTIONS because you need both halves for a reaction to happen. You use half reactions to balance redox equations by making sure the number of electrons lost is equal to the number of electrons gained. Since the same number of electrons are lost as gained, the half reaction can be added as they are and the electrons will cancel giving you

  Cu^2+ + Zn -> Zn ^2+ + Cu

The activity series can be used to predict which equation represents a reaction that will occur. From the activity you can see that zinc is more reactive metal than copper, meaning that copper is less likely to react than zinc. 

I feel like for the first time I’m not overwhelming you with things that make zero sense. This one is going very well and look we have on more step and boom, DONE. 

So the next question you should be thinking is when is a metal not a metal? Come on lets be real no one is really thinking that unless you’re a chemist. Metals in general are solid, shiny, ductile, malleable, and conductive of heat and electricity. Hydrogen is none of these things but is still included in the metal activity series. This is because hydrogen takes on the positive nature of a metal in its role in strong acids such as hydrochloric, sulphuric and nitric.  The most important reason to include hydrogen in the metal activity series  is because these acids are simple and convenient reagents which can quickly establish where an unknown metal stands in the series. 

Problem

Photo on 26-04-2017 at 9.33 PM

I couldn’t get all of it yesterday so i waited until we went through it in class.

I showed which i did for hw and what i did in class

Stoichiometry

It’s a beautiful day, lets learn some chemistry, 

In the world, you just grow up knowing things. You may not understand what i mean but its simple; everyone knows a dozen is 12 of something, a century is 100 years or a decade i s 10 years. Everyone just grows up knowing this. Well, chemistry has a similar concept, that is a mole which is 6.022 x 10^23  is just a representation of a quantity just like the ones i listened above where small small objects are quantified by one word. Thankfully the actually number of a mole doesn’t matter in this section really it is just understanding that one of anything is always the same quantity and 3 moles of something is the original quantity time 3. Okay so we started off pretty good, nothing too bad but now to good stuff.

 One mole of any single atom or molecule has a mass equal to its atomic mass which is expressed in grams. this part is easy as it is simply found on the periodic table. who would of ever though chemistry would entail just looking at a chart. So the molar mass is simple just on the element usually the last number. For example, Oxygen has a molar mass of 16 amu, but a molecule O2 is made of 2 oxygen molecules  resulting in one mole of oxygen molecules be 32.00g. Componds follow the same procedure but you first separate the elements figure out the individual molar mass then add them together. To me this is like baking a cake, you want one cake you use 2 gets and 1 cup of flour but if you want to cakes you have to double the amount of ingredients. 

This section is kind of boring not going to lie, but hopefully this is the basis and build up to something so exciting and fun. One mole of almost any gas at standard temperature and pressure will occupy the same volume, 22.4 L. Standard pressure is close to the pressure we live at. when the temperature of a gas increases, the volume occupied by the gas increases. So while one mole of a gas at standard condition will occupy 22.3 L one mole of the gas at room temp will be a bit larger

Stoichiometry is a calculation that involved calculating the number of moles of one chemical in a reaction based on the number of moles of one of the other chemicals in the balanced chemical equation. The coefficients from the balanced equation set the the proportions which relate the number of moles any reactant or product in the reaction to the other reactant or product. so I’m sure you’re wonder what i just said, but i got you. example 

N2 + 3H2  -> 2NH3

This simple equation is telling us so much: believe it or not

It tells us that one mole of nitrogen and three moles of hydrogen molecule produces 2 moles of ammonia. The rations never change because they have fixed formulas.

This also applies to the idea that if you use three times as much of a starting material you will make three times as much product. So this is kind of like when factories make peanut butter, they have one formula but multiply it by the amount they want to make. To mathematically or chemically figure this out, you use dominoes which is really just unit measure with liens around it to look like a domino. 

Chemist kind of have life a little rough because there is no equipment that measures moles directly. This makes chemist have to find a suitable unit that they can actually be measured. two measurements that are easy to make in the lab are mass of a solid or liquid and volume of gas. You then use the stoichiometry method,  you convert known mass of any chemical into moles and then convert your answer in moles back to grams aka unit measurement. 

I hope you’re still there! you know what i have an idea! Stand up take a deep breath and do 5 jumping jacks to help boost your concentration. We will learn this chemistry today. 

So now that we are back, lets look back a this method. SO did you notice when you did the unit measure that all the calculations could cancel each other out to give proper units for the answer. Well it has a fancy name: dimensional analysis. It just really tells you that the method of solution is reasonable. 

When a reaction is carries out and the product is recovered and measured, it is common to find that less than 100 percent of the expected product is found. This is because there are many ways to lose small amounts of the product. Scientist noticed this and report a percent yield for a reaction. 

So, now lets see why this matters in the real world. So stoichiometry allow chemist to control the results and produce the desired effect by predicting the amounts of these new chemicals. You can inflate a ballon to move a lever by a specific amount.

 

Well i  hope i didn’t bore you to death  but now we know stoichiometry and i can actually spell it now!

 

 

 

Energy and Entropy

I bet you have been missing me, I know, I know, i haven’t been here in a while but i will just make this blog that much better to make up for it.

Suns out and its a beautiful day to learn some chemistry, am i right?

So in chem today, i felt like a clown for some reason because we were constantly blowing up some balloons, which reminded me of the parties i went to when i was a kid. So we made a balloon inflate using different materials to generate carbon dioxide. 

 

Most chemist prose the question: Does the Generation of the Gas Require Energy Input or Does it Release Energy? As i am nothing near a chemist i did not even think of this but my teacher said thats really what we should be think about so, i tried it. It was clear that wasn’t one clear and easy answer. Matter was very much involved and the basic concept of the fact that matter can undergo a change. Matter often changes in energy which means it will move from being stored in one form or place to another form or place. despite this, interestingly, the total amount of energy in the universe stays the same. Matter doesn’t work like magic, so when it is involved in a change and loses energy, the energy must go somewhere and vice versa.

For people like me who don’t just see chemistry the first time, we can relate energy chang to water. ice cubes melt on a heated stove as it gains energy while also the water will increase in temp as it again gains energy and lastly, water boils into vapour as it gains even more energy. on the flip side of transferring water it is removing the energy. 

 

So yeah I’ve been using the energy a lot: the energy gains, the  energy loses, the energy, energy but do you even know what i mean? So, when you add heat energy to something the particles gain the energy making the particles have more than before the heat was aded. So as most things in this world work, the energy has to go somewhere, one place being in the making of particles move faster or could go into changing the bonds that exist between atoms and molecules. 

Bonds are only ever involved with molecules! they hold the atom in an individual molecules together.  

Attractive forces exist between molecules in solids and liquids. they prevent them from separating to form a gas. This is like what double sided tape does. it holes things together to keep the shape and form of something. 

The input of energy is what it takes to overcome weak intermolecular forces or chemical bonds. These forces are involved in a phase change of a substance. on the flip side, chemical bonds are much stronger than intermolecular forces of attraction so it takes a lot more energy to break bonds bonds are always broken so that new and different molecules are forming in every chemical reaction. Both backing chemical bonds and intermolecular forces of strain it takes energy input

Attractions between molecules cause a phase change where energy is given up and heat energy  is released to the surrounding. Most processes you will encounter involve both breaking and forming bonds between molecules. 

Perspectives, the same exact story can easily be interpreted in different ways because of perspectives. Chemistry also has perspectives, which is always that of the reactant. the energy change from start to finish in the chemicals is a positive one and is called endothermic change. this is because heat energy goes into the chemicals. on the opposite side, you have exothermic which is when the change in energy for the matter is negative.

Imagine a Pre k classroom with no children in it and one with 60 toddlers in it. One of the rooms would be fully organised and neat where as my bet the one with 60 toddlers would be quite disorganised. just like this chemist like to speak in terms of disorganisation. they consider disorder by how many arrangements of particles are possible or how spread out. A number line can be used to measure disorganization. 

gases have their molecules very spread out. Reactions that create gases from solid and liquids have an increase in disorder. all our methods we did increased disorder. solid – liquid = increase disorder. 

This idea of disorder is quantified under the name of entropy which is given the symbol S. the Entropy that a material has is a measure of its amount of disorder. 

Okay i know that was a long one for me to come back with ! but next time hopefully won’t be as bad

see ya

 

Chem Talk 8

Hello World,

clear, delicate and fickle: the wonders of GLASS

its pretty simple, that is making glass: you mix silica , sofium carbonate and calcium carbonate while heating until it becomes a liquid. next allow it to cool. BOOOM you have just made glass. well to get a little more complex to make glass have colour you just have to make their be impurities. wow who would of thought impurities would come in handy. To make different coloured  glass metal oxides are added. to get blue you add cobalt oxide and copper oxide and for yellow and green add ion oxide and chromium oxide. The compounds absorb different coloured light from the white light passing through them and transmit the colours you see. In the glass world, the elements were named after some of the colours they made, for example rhodium which makes rose coloured glass. In greek rhodon means rose. 

This technique is also used in ceramics. i think ceramics is pretty cool, especially when you get to use that spinny machine. Anyways back to chemistry.  In the colouring stage of ceramics it all depends on the concentration, firing temperatures and conditions of firing. A few colour element combos are iron =amber to dark red, cobalt= blues and copper = greens. Ceremic artist can glaze their sculptures to add colour but also to help slow down the deterioration process. 

« Older posts

© 2019 Tayla'a Chem Blog

Theme by Anders NorenUp ↑