Checking up 1-7
1.) For a change to occur spontaneously, a chemical reaction continues to occur on its own once it begins.
2.) “Will it continue to occur” and “How fast will it occur” determine if a change can occur spontaneously.
3.) To tell if it is exothermic or endothermic, you have to look at the locations of the reactant energy and project energy which indicates whether the overall enthalpy change is either one.
4.) Energy in an exothermic reaction comes from if the starting point is higher than the ending point and then the system releases heat energy to the surroundings.
5.) Two things that chemists use to speed up a reaction in a MRE heater is something with more surface area and something that can act as a catalyst, like iron.
6.) A catalyst provides a lower-energy alternative pathway for the reaction to take so they have enough energy to get over the energy barrier.
7.) When there is a catalyst the barrier is smaller so it is easier to get over but when there isn’t a catalyst the barrier is bigger and the bump is harder to get over. However in the end the products go down and end in the same place.
This Chem Talk was about Thermodynamics. I have never learned about Thermodynamics before this. It is a completely new topic for me. Looking at the word I would have guessed it would be about temperature because of the thermo. The whole Chem Talk was completely new material for me. I mainly learned about how some reactions can continue to occur on their own once it begins. This reaction is known as spontaneous. It surprised me that it was called spontaneous because this is a word I have heard and used before in everyday life, outside of chemistry. Thermodynamics and Kinetics are both theories that predict when it will occur spontaneously and how is can speed up and slow down. Change in enthalpy is when an energy change occurs at constant pressure. This is a completely new concept for me. If the change is negative the reaction is exothermic and if the change is positive, then the change is considered to be endothermic. It is pretty easy to see if the equation is endothermic or exothermic. You can tell by the locations of the reactant energy and the product energy, which indicate whether the overall enthalpy change is either one. Something that I understood was that when the starting point is higher that the ending point, the system releases heat energy and the enthalpy is negative. Now when the starting point is lower than the ending point then the system absorbs heat energy and the enthalpy is positive. Next I learned about “the bump.” The bump is the height of the reactant energy. This is called the activation energy and is always positive. The top part, which is the state in-between the reactants and products is called the activated complex. The last thing I learned about was the catalyst. A catalyst is a substance that speeds up a chemical reaction without being used up itself. Overall, this was a very new topic for me and most of it is something I haven’t even heard of before.
Checking up questions 1-5:
1.) NaCl conducts electricity because when the crystal s dissolve in water the sodium ions and chloride ions separate from the crystal. They can move around in water. Molecular compounds do not break up into ions when they dissolve. The means they can not move around in water and can not conduct electricity, which is why C12H22O11 cannot.
2.) An electrolyte is a substance that dissolves in water to make solutions that conduct electricity and non-electrolytes are molecules that do not form ions in a solution. An example of an electrolyte is NaCl.
3.) The Zinc electrons come from the zine metal and then travels through the wire. Then the electrons reach the copper and the copper takes them. Reduction then takes place.
4.) The anode of a battery is when oxidation takes place and the electrons are released into the circuit. The anode is negative when giving away. It is where the electrons are released. It could not exist without cathode.
5.) The cathode of the battery is where reduction takes place and the electrons are received. The cathode is positive when receiving. It is at the end where the electrons are received. It could not exist without anode.
This Chem Talk was mostly about solutions that conduct electricity and the charged particles that go along with it. I have heard about solutions before in 8th grade. I have also talked about conductivity, but I have never talked about solutions that conduct electricity. By reading through the Chem Talk, I understood it pretty well, and I saw the connection between solutions and conductivity. Specific substances only dissolve in water to make different solutions. These solutions then conduct electricity. The substances I am referring to are called electrolytes. Also, when this happens charged particles are able to move around. It is considered electrolytes, if the substances change into charged particles when dissolved. We learned about ions, before learning about electrolytes. The charged particles, ions, are usually when the compounds are made of positive metal ions and negative ions. An example of this is NaCl because it follows all the rules and is considered or classified as an electrolyte. I read something that was pretty interesting to me. It was when I read that compounds that don’t break up into ions when they dissolve are molecular. The last sections we read was about oxidation and reduction. It surprised me to learn that is used in a battery, which is composed of two half cells. It was something I had never really heard before. An anode is the part where the oxidation takes place. The place where the reduction takes place is the cathode. These two ideas rely on each other and cannot exist without each other. In this Chem Talk, I learned a couple new things, but I also reviewed a couples things like the activity series and how it relates to this.
Chem to go 3-4, 7-11
3.) a.) Al b.) Fe c.) Al
4.) The pair Al and Pb
(Al -> Al3+ + 3e-) x2
(Pb2+ + 2e- -7gt; Pb) x3
2Al + 3Pb2+ -7gt; 2Al3+ + 3Pb
7.) c.) It’s the same.
8.) b.) Zn(s) –> Zn2+(aq) + 2e-
9.) d.) It loses a electron.
10.) b.) electrons from Cr3+ to Al
This Chem Talk I learned about a couple new things I have never learned about before. The newest thing was probably the properties of a metal and what a metal can do. For most of the metals on the periodic table, they don’t appear in nature as a pure metal usually. I had never heard of scientists named alchemists before. I thought it was really cool that they were able to discover that some metals react more easily with most metal ions solutions than other metals do. Another thing that was interesting was I had never heard of this before. Another new thing I learned about was called an oxidation-reduction reaction. When I first read about it I thought about oxidation and how that would probably be about oxygen and the oxidation because that’s what electrons do. I had an idea of what reduction was but I wasn’t completely sure what it meant in scientific ideology. Something that confused me was how some of the equations have to be written backwards with the arrow at either the beginning or end. This is confusing and something I will definitely have to remember for the test. Something weird about that rule though is the fact that naturally, it only occurs in one direction. Some metals might now be a metal like hydrogen. Even though Hydrogen has no properties of a metal it still takes on the positive nature of a metal in strong acids. An example of this would be hydrochloric, which is HCl vs. NaCl. In this Chem Talk I learned many new thing, but I also learned some of the things before which was also nice as a review. Also, some of things I was able to clearly understand by myself.
In this Chem Talk I learned a brand new idea of stoichiometry. I had never learned about it before nor have I ever heard of it. In this section mainly about stoichiometry you had to use balanced equations. Earlier in the year we had used them before, but I still had to remind myself what they were and review them. Suring the process, we had to use something called Moles, which I had of before. When thinking about molar mass, one mole is always equal. The molar mass is the atomic number, of a single kind of atom. When you start using volume, gas has the same volume every time which is 22.4 L. However, this is the only rule when the air is at standard temperature and pressure. Being about to rely on a constant makes it a bit simpler. I did not have to do any more calculating for that number because it was given to use. With stoichiometry, you have to complete a bunch or equations. The equations are set up like fractions and are multiplied across. An important rule to remember, is about checking to make sure your units are lined up correctly to be able to cancel out. When solving one of these problems you have to remember to think about all the factors your beginning with and what you want to end with. Then you set up the factors like a domino effect and multiply across. Always remember to cancel units and in the end have the unit you needed to find. This would be called dimensional analysis. This is another thing that I had never participated in. The real world has some stoichiometry. Some of these things surprise me but also some of them don’t. When working with new substances and the converting part of it, it can result in new chemicals that can cure cancer. This was the one that caught my eye the most because anything that can help cure cancer is always great. New chemicals found can be used for many things in our everyday life and the study of stoichiometry can help us with this. It’s amazing to think about how things we do right now in Chemistry, are things we could be working on in the real world someday and some people already are working with these type of things. .
In this Chem Talk they mostly talked about the Law of Conservatiion of Matter. Balanced chemical equations are an example of the law of conservati on of matter. This is something that I had never realized. I have heard of the law, but I have never really studied it before. The law states that the amount of matter present before and after a chemical change remains the same. Matter cannot be created or destroyed, but it can change form. This means that teh same quantity of each element must enter and exit a chemical reaction. I knew that matter could not be created or destroyed, but the fact that it can change form surprises me. When chemical equations are written, the quantity of that element on the product side, although the atoms of the element may be bonded differently. ANother thing that surprised me was the fact that Democritus, Heraclitus, and Aristotle, were among the first to postulate that there was an “equivalence of matter”. This is surprises me because I would have thought someone would have come up with this way before, not just 2500 years ago.
1.) Most gases have very little attraction between their molecules because the molecules are very far apart from each in a gas. The shape of the nonpolar molecule causes this and sense a gas has a shape with the molecules spread out very much, their is little attraction between each other.
2.) a.polar b. nonpolar c. nonpolar
4.) The intermolecular forces in water are stronger than those in methane.
This Chem Talk had many things we learned in the fall. I think it was a nice review and reminder of some of the things we should be able to understand and remember but also a couple newer things too that I learned for the first time. The newer thing I learned about was called Intermolecular forces vs./& kinetic molecular motion. The intermolecular forces was the relation to the number and position of electrons. The kinetic energy overcame the forces when heat was added and the next state of matter took place. The energy got greater when the heat was added. I thought this was really interesting. I have also heard that for plants, the water is carried throughout teh plant structure through intermolecular forces. I also thought it was interesting that intermolcular forces are the basis of genetic coding. A new term and idea I learned was nonpolar molecules which have shapes and bonds that are symmetrical. Something I found that was fascinating to me was when the size of the nonpolar molecule increased, the attractive forces between the molecules also begin to increase. A idea we learned before in teh fall term was electronegativity. I remembered this after I read it, but it was a good refresher for me. The atom with more electronegativity is the atom that pulls the other atoms towards them. A polar bond is the act of a partial negative charge atom and a partial positive atom pulling towards one another. In this section, I thought that there was a little review which definitley helped, but I also think that a lot of the new information we learned was really interesting.