Chem Talk Section 8 Chapter 4

When describing a change of a reaction, a chemist would talk about the system and the surrounding. The reason why is because the system and the surrounding together would make a “universe.” There are two things for the system, an open system, and a closed system. An open system is when energy can pass between the system and the surrounding. A closed system is a system that “is isolated from the surroundings and heat” cannot leave or enter. 

When the heat is leaving the system, the surrounding is gaining the energy while the system is losing energy. Which means that the change of the enthalpy is delta less than 0. If the system is gaining energy, it does not come from the surrounding. The law of conservations of energy “states that the energy cannot be created or destroyed,” it moves from one place to another.  So for example, when you touch an object and it feels cold, that means that the system is gaining energy from your hands, which is the reason why your hands feel cold. Which in this case the delta H is more than 0.

Whenever a change is undergoing, the particles in the system are rearranged. This new arrangement can either be disordered or ordered. When it the arrangement is more disorganized the entropy increased (delta S is less than 0) when it is less disorganized the entropy decreased (delta S is more than 0).

If two elements change during their reaction, it is in the line of being spontaneous, the reaction will be spontaneous. However, if both reactions does not change, the reaction is not spontaneous. If one reaction changes but the other does not, it still will be spontaneous. 

Chem Talk 7 Chapter 4

For our lab, we made a reaction. Recording the time, and the temperature of the reaction. My lab partners and I “explored a chemical reaction that contains to occur on it own, once it begins”, this is called spontaneous. And we also explored how fast the reaction occurs. 

Chemist and engineers need to be able to control chemical reactions, and they do it by being able to predict when a reaction can occur, and what they can do to speed it up, or to slow it down. This is called thermodynamics, which is used to answer a question that a reaction can occur by itself. And another is called kinetic, it is also used to answer a question “How fast can a reaction occur?”. 

There are 2 things that determine if a reaction can occur spontaneously. One we can see is if the reaction gives off any heat, or if it gaining heat. The second is that d reaction during the reaction, the particles in the can be disordered or less disordered. The two things that can really work together and be spontaneous is when the reaction releases energy and the particles are increased in disorder. But, when one reaction is spontaneous and the other is not then whichever that is is stronger in control during the reaction is spontaneous. 

The main points of reactions are:

  • “the bonds between the reactants break and new bonds form to make products”
    • however, in order to break bonds, energy is needed. So the bond breaking is an endothermic change
  • Making the bonds releases energy, so this is an exothermic change

An enthalpy change is when an energy change happens during a constant pressure. So another way of showing this change is by making an energy diagram. This diagram shows the process of the reaction “from reactants to products along the horizontal axis”. 

It doesn’t matter if the reaction is endothermic or exothermic because the bonds between atoms will be always broken before any new bonds can be made. To break the bonds, energy is needed, this is an “activation barrier or the bump”, where the energy level rises. This is called the activation energy. 


Chem Talk Section 6

For our lab, we conducted electricity using some kinds of dissolved substance in water, which is called electrolytes. In order to find out if we actually conducted electricity, we used a conductivity tester. 

In order to conduct electricity, there are two conditions that are needed. The charged particles (the substances that broke into charged particles when dissolved, which is called ions) “must be able to move around”, and because these particles can move, a solution for example sodium chloride was able to conduct electricity. However, sugar/molecular compounds, do not break up into charged or negative ions, like sugar, when sugar is dissolved in water, it is still sugar. And because of this, molecular compounds do not conduct electricity. 

One important key of a battery is that the electricity only runs in one direction, and this is because of the two metal electrodes that are used as half-reaction. 

Chem Talk Section 5

Our lab for today was to scale the colors that were reflecting from the LED. We would light up the LED using some wires, a battery, and a 100~. 

 A physicist made a “planetary” model of an atom, using this he found out that electrons would travel in circle paths, which we call orbits around the atom. He said that each electron has its own number of electrons, the farther the electron is from the atom, the higher its energy is. When these electrons gain energy, it jumps to a higher orbit, and when coming down to its original orbit, it will release color. 

The colors that us humans can see are part of electromagnetic spectrum, other parts of the electromagnetic are, the ultraviolet, infrared, x-rays, gamma rays, microwaves, and radio waves. 

Many people would interpret radio waves “as being similar to the light waves”, however, they are not. Radio waves have something called frequency, this tells you the number of the cycles or waves that were being produced each second. There is also a wavelength, the distance from each wave. As “you go down the wavelength”, it would gradually get smaller, when the frequency goes up. 

A Photoelectric Effect is a “collision between a particle of light and an electron on the surface of a metal”. 

Chapter 4 Section 4 Chem Talk

Today in class we did a lab on turning a LED on and off by using metals. We used a metal to turn off the glowing LED light. 

Metals have important properties. For example, they can conduct electricities, so they are used in electrical circuits, they can conduct heat, so they are used in kitchens or cookwares, they are also used to build strong structures because they can be shaped into different shapes. 

Many metals are reacted with hydrogen and are founded in nature. Positively charged ions are involved in solid crystals or dissolved in water.When an atom reacts with another in the metal, the electrons that are placed in the metals are changed.

An oxidation-reduction reaction is when a reaction occurs between neutral metal atoms and metal ions. The meaning of oxidation is giving up electrons. The opposite of oxidation is a reduction, which is when the metal is receiving electrons. We use this in equations, for example, every element that loses electrons, it means that the other will be gaining the lost electrons. 

Metals, in general, are solids, shiny to the eye, ductile, malleable, and they can conduct heat or electricities. So how to differ a nonmetal and metals are that they have to fit in all 6. 

Chapter 4 Section 3 Chem to go

1.) a.) CO2  

b.) Heating of the substance that reacted to or released.    

c.) Yes, it is. Because without the other substance, the reaction would not have happened.      

d.) yes, it will. The reason why is that the amount of two substance together will be different when adding small amount of the reactant to a large amount of the product. 

2.) ?

3.) a.) 1 mole = 12 g of C

b.) 1 mole of Al = 27g of Al

c.) one mole of NH3 = 17g of NH3

d.) one mole of CaCO3 = 100g of CaCO3

4.) a.) One mole

b.) 13.5g of Al in .5 mol of Al

c.) around 50g (?)

e.) 2 moles of NaAl(S04)2


Chapter 4 Section 3 Chem. Talk

In this lab, we learned about the unit conversions between elements, moles, liters, and more. We also learned how to get a mole from an atom. For example, oxygen has an atomic mass of 15.99 AMU that can be found in the periodic table. This mass is called molar mass. So if oxygen has two of itself, O2, it means that it is the double the size, which means you have two moles of oxygen. For water, add up all the atomic mass of each atom: 1.01 amu + 1.01 amu + 16.00amu which in total is 18.02 g => this is one mole of water. However in order to find the molar of gas, depending on the standard temperature and the pressure.

Calculating the volume of the gas, using the number of moles of the reactants, is called stoichiometry. 

To solve a stoichiometry problem we need to figure out the measurement of the beginning of the problem and know what you need to measure for the end. 1.) We can use the molar mass of the substance which we need to use the periodic table to find the total amu of the whole molecule. 2.) We can use the coefficients from the already balanced equation. 3.) or we can use the volume of the one mole of the gas it takes up. 

Calculating these problems is dimensional analysis which says that the solution of the problem is reasonable. 

Chem Talk Chapter 4 Section 1

In the lab, we created CO2 has and used the gas to blow up a balloon, and using the balloon to life a lever. Every time we would redo the lab, we would get different results, at the same time the balloon will be small or will be big. The gas blowing up the balloon is because of the matter, the change of the energy in the molecule will determine the move of an energy. 

When we add heat to something, the particles will gain energy from the heat. However, when the particle was enough heat, the leftover heat does not stay there. Some of the energy that was left behind will go into the bonds between the particles and change them, making the particles to move faster. The bonds between molecules will hold together and attract forces making molecules bind together. This attraction will happen between molecules in solid and liquid forms. The attraction will hold the molecules of solids and liquids together, leaving no room for gas. This attraction can also cause a phase change between molecules when energy is giving up and the heat energy is released. 

Energy can be positive or be negative. When energy is being added to the molecule it is called endothermic, and it is positive. When heat is leaving the molecule, it is called exothermic, and it is negative. 

Also depending on the form of the molecule, the matter can be ordered or disordered. If the molecule is solid or a liquid, the order of the atoms in the molecule is very strong. If the molecule if aq. or a gas, the molecule is very disordered becase the atoms can go anywhere they want. This is called entropy. 

Chapter 4 Section 1 Chem to go

1.) a.) exothermic   b.) endothermic    c.) exothermic

2.) a.) increases.     b.) decreases.          c.) increases

3.) For the first equation:

      a.) 2Fe(2)O(3)(s) is the product, and 4Fe(s)+3O(2) are the reactants.            

      b.) It decreases in disorder because the molecule turns solid. And solids are very ordered with low entropy. 

For the second equation: 

      a.) 2KClO(3 is the product, and 2KCl + 3O(2) are the reactants

      b.) It decreased in disorder because the molecules got stronger

4.) exothermic so A

5.) B

6.) C