The following Chem Talk is called Thermodynamics. When I first heard this word, I had no idea what is meant or what is was about. The whole Chem Talk was completely new to me. Some of the topics stood out to me and interested me. I learned that some reactions can continue to occur on its own once it begins and that this reaction is called spontaneous. This made total sense because of the meaning of the word when it is not related to chemistry. Thermodynamics and Kinetics are both theories that predict when it will occur spontaneously and how is can speed up and slow down. When a energy change; however, occurs at a constant pressure, chemists call this “change in enthalpy.” If the change is negative the reaction is exothermic and if the change is positive then the change is endothermic. These two words are completely new to me. It is pretty simple to tell if the equation is endothermic or exothermic. You can tell by the locations of the reactant energy and 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 interesting thing I learned was about the catalyst, which is a substance that speeds up a chemical reaction without being used up itself. For example, anything with more surface area makes the reaction faster and also iron is one in a reaction between magnesium and water. On a boarder stance, a fire is a perfect example of all of this because it is exothermic, which releases heat to everyone around it.
Checking up questions 1-5:
- 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.
- 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.
- 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.
- 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.
- 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.
In the following Chem Talk I learned about solutions that conduct electricity and the charged particles that go along with it. Before reading this, the topic was not really something I thought about. Once I read the whole chem talk though everything made sense. Certain substance only dissolve in water to make different solutions. These solutions can then conduct electricity. The substances that can do this are called electrolytes. When this also happens charged particles are able to move around. If the substances change into charged particles when dissolved then it is electrolytes. Before this we learned about ions. The charged particles that are ions is usually when the compounds are made of positive metal ion and negative ion. An example of this is NaCl because it follows everything and is classified as a electrolyte. Something I found interesting was that compounds that do not break up into ions when they dissolve are molecular. In the last section we learned about oxidation and reduction which is used in a battery which is composed of two half cells. This part was brand new to me. The part where the oxidation takes place is called the anode and the place where the reduction takes place is the cathode. Each one can not exist without the other. We have to write out the redox like before which is something that I got pretty easily. Part of the compound will go through the salt bridge and into the other half cell and will make the battery work. We already knew about the activity series and I have a pretty good understanding on how it relates to this and vis versa. I learned some new things but also reviewed and used some previous knowledge in this Chem Talk.
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- -> Pb) x3 2Al + 3Pb2+ -> 2Al3+ + 3Pb
7. c.) the same
8. b.) Zn(s) –> Zn2+(aq) + 2e-
9. d.) loses a electron
10. b.) electrons from Cr3+ to Al
In the following Chem Talk I learned some new things. The thing that was not new to me was the properties of a metal and what a metal can do. Most of the metals on the periodic table however do not appear in nature as pure metals commonly. A new scientist I learned about is alchemists. I have not heard about alchemists but I found it cool and interesting that they discovered some metals react more easily with most metal ion solutions than other metals do. I find it weird that they found this out and I had no idea what they were before reading this Chem Talk. A new reaction I found out about and learned about was called an oxidation-reduction reactions. When I heard it though I had a sense of what it was going to be about because I know oxidation is related to giving away, which is what the electrons do. I had a feeling on what reduction meant in this place, which is to receive and that is what electrons take part in doing. It is smart that they call these reactions half-reactions because both sides react and based on how many electrons you give away, you will get that many electrons back by the other element. Something I found that people have to remember is the equations might be able to be written in either direction but the reaction can only occur naturally in one direction. Some metals might not be a metal and a example of this is hydrogen. Hydrogen has no properties of a metal but it takes on the positive nature of a metal in strong acids. An example of this would be hydrochloric, which is HCl vs. NaCl. Throughout the Chem Talk I learned a lot of new things but I also noticed some things that I learned previously and some things I could figure out on my own.
In the following chem Talk I learned a completely new topic called stoichiometry. I had no idea what it was and or how to do it. In this section you have to use balanced equations, which we already learned about in the past, to set of the conversions we would have to later complete. During it you have to use something called moles, which I knew about before. One mole is always equal to the molar mass, which is the atomic number, of a single kind of atom. When volume comes into play, gas has the same volume, which is 22.4 L, when it is standard temperature and pressure. I really like this because you only have to remember one number for a standard gas, which makes it way much easier to work with. Now with stoichiometry, you have to complete a bunch or equations. The equations are set up like fractions and are multiplied across. One important thing to remember if to make sure the units cross cancel down to the right. That is the first thing I check when completing a problem with converting. 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 name is interesting to me because it is such a long name for such a quick and easy procedure. 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.
In this Chem Talk we did more practicing with balancing equations. From the past, we learned how to balance equations before this section. The point of balancing is to make sure each side has the same amount of a certain element as the other side. For example if you start with two oxygens on one side then you have to produce or end with two oxygens on the other side. Also with this section we learned how to draw out the equations using coloring pencils. I found it interesting and helpful because now I could see the reaction drawn out and I would be able to see which element is reacting with which element visually. Balanced equations are examples of the law of conservation of matter. Before this class and year I learned about the law of conservation of matter and knew what the book was talking about when I read it and that everything is made of matter. Over the year we did a lot of practice of with balancing equations. The amount of practice has helped me and I now feel really confident when being asked to balance out equations. Knowing how to balance equations will help me throughout the rest of the year when completing other sections and units.
The following Chem Talk had some things that we should have known from the fall. There were also somethings that was introduced for the first time to me. This was called Intermolecular forces vs./and 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. This is interesting to me it is just like ice, water, and steam. The ice freezes then heat is added and energy overcomes some force, then turns into water and heat is added and energy does its magic, and lastly it is steam. The particles distance themselves as the heat and energy increases. 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 was electronegativity. 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. The section I read about had a little review but had many new things that interested me and made sense when all put together.