When speaking of change, chemists refer to the system and the surroundings. Together, the system and the surroundings make up the universe. You choose the system that you want to investigate and you can imagine drawing a dashed surface around the system, to separate it from the surroundings. When considering change you think about what the system is doing. we stretched the rubber band and asked if it was creating heat energy or releasing it. If the system is an open system, energy can pass between the system and the surroundings. For example a teakettle heating on the stove is an open system. A closed system is a system that is isolated form the surroundings and heat can neither enter nor leave. This is very, very difficult to achieve. An attempt at a closed or isolated system is a thermos bottle. As we know a thermos bottle slow the movement of heat, but eventually the hot soup or cold beverage in the thermos bottle will exchange heat with the surroundings. when heat energy is realized from the system the space around it gains that energy as the system is losing energy. when a system loses energy there is a loss in the amount of enthalpy that the system contains. when heat energy is obsessed by a system the surroundings must give that heat energy to the system. energy must come from somewhere and as stated in the low of conservation of energy, energy cannot be created or destroyed. in the lab we worked with a rubber band, weight, and hair dryer. we hung there rubber band with the weight at the bottom and measured how far the bottom of the weight was from the table. we then heated up the rubber band with the hair dryer and measured again. our results were that the band contracted under heat and expanded while cooling. the second part of the lab was to place the rubber band against your forehead and took note of the temperature. we then stretched the band across our foreheads and took note of that temp. the result was that stretching the band make its get hotter which means it is releasing heat and the non stretched band was cool which means it was gaining energy.
Will is continue to occur? how fast will it occur?
In this lab we learned about a chemical reaction that continues to occur on its own once it starts. this spontaneous. we also explored the factors of how quickly a reaction will occur. in the case of a reaction that produces heat energy controlling the spread of the reaction will let you control how quickly the heat is produced. in oder to control chemical reactions they need to be able to predict when reactions will occur spontantiouly and need to know what can be done to speed up or slow down reactions. one theory of this is thermodinamics. the other theory is called kinetics. there are two factors that determine if a change can spontaneously. one is that if the change gives off heat energy when it occurs or aborbes heat energy when it occurs. the other is if the change results in particles becoming more disordered or less disordered. two rules that apply to these questions are that lowered energies are more stable than higher energies and everything tends to become more disorganized over time. heat energy changes endothermic and exothermic reactions.when chemical reactions happen bonds in the reactants break and new bonds form to make products. breaking bonds requires energy input so bond breaking is an endothermic change. forming bonds releases energy so bond forming is an exothermic change. activation energy is the bump in the graph which measures the reactants energy and is always positive. in the lab we tested different substances in water and watched their reactions. the Mg and water reacted very slowly and only slightly bubbled. the Mg and NaCl with water was quicker and heated up a little.
Substances that dissolve in water to make solutions that conduct electricity are called electrolytes. in the lab we used a conductivity tester to find out if a solution conducted electricity. for a solution to conduct electricity it has to have charged particles that can move. in out lab all the substances we used were disolved in distilled water. on the substances that broke into charged particles when disolved were electrolets. there are two conditions that are necessary for a solution to conduct electricity. there must be charged particles and they must be able to move around. some of these particles are called ions. usually it consists of a positivly charged metal ion and a negotiably char3ed ion. In this lab, electrons are produced by the oxidation of zinc metal at the anode. while the batter is operating, the zinc metal elected is slowly undergoing a reaction. Neutral zinc metal atoms make two products according to the equation. Zinc ions and elections are produced at the anode. the zinc ions either the zinc nitrate solution while the electrons travel thought the wire. Eventually the electons reach the copper metal electrodes where reduction then takes place. when electrons reach the copper cathode they enter into the reduction half reaction. this is where copper ion from the solution combine with electrons and make neutral copper metal atoms. you eventually get negatively charged nitrate after the solutions dissolve in water. the only place for the NO3- ions to go is though the salt bridge.
in the lab we examined colors that make up visible light and used LEDs to explore a glow in the dark strip. light is a form of energy known as electromagnetic radiation which includes x-ray, ultraviolet rays, microwaves and radio waves as well as visible light. Visible light is detectable by the human eyes. light can be determined by wavelength and energy. wavelength is the distance between two corresponding points of a wave. in the lab we determined the wave length of different colored LEDs. we did this by shining a red, orange, yellow, green , blue, and purple light into a wave length measurer. this told us the wave length of the LED. we also checked each light to see if it was phosphorescent. only the blue and purple lights were Phosphorescent because they are the only lights that have more energy then green light. they need to have more energy then green light because they glow green.
Metals are shiny (or can be polished to shine. Metals are used in electrical circuits because they conduct electricity. Since they also conduct head they are used in many forms of cookware. They can also withstand really hight temperatures so they are used to build strong structures. metals are also bendable so they can be made into many different things such as nails, flat surfaces and boxes. most of the periodic table is metals and if you draw the inviable staircase everything left of it is a metal. most metals are not naturally pure metals. they are likely to be found in their ionic state. reactions can also be caused between neutral atoms and metal ions and create a reaction called oxidation. Reduction is reviewing energy, while oxidation is giving elections. in the lab we experience both reduction and oxidation.
- a) exothermic: antacid tablet is releasing energy, water absorbing it b) exothermic: water turing from gas to liquid is the water releasing energy c) endothermic: the oxidation is the loss of energy, copper is gaining energy
- a) its disorder is increased because the solid tablet and liquid water are creating a gas b)increase because gas is turing into liquid c) cannot tell
- a) reactant: 3O2(g), 3O2(g) Products: 2Fe(2)O3(s), 2KCIO3(s) b) both increasing bc they are both going from solids to gasses
In our chem lab today we tried to make a ballon fill up to six inches with CO2 gas. There were four different methods tried to achieve this. The first was sodium bicarbonate and acetic acid. In normal language this is just baking soda and very acidic vinegar. This method was successful in inflating the balloon. The second method was calcium carbonate and hydrochloric acid. This way also inflated the ballon. The third method was just heading calcium carbonate over an open flame. This did not work. However in theory if it was headed at a much much higher temperature it would work. Lastly, was heating a carbonated beverage on a hot plate. This did work and inflated the ballon nicely. The expansion of the ballon was caused by the energy undergoing a change. In a few of the methods, heat was used to find out if it would cause a reaction that would inflate the ballon.
- Na=1 F=7 Mg=2 Ne=8 P=5 Al=3
- Na lose one. F gain one electron. Mg will lose two. Ne will stay the same. P will gain three. Al gain lose three. b) Na=+1 F=-1 Mg=+2 Ne=stay the same P=-3 Al=+3
- The rule is the outer shell has to be full or empty so the outer shell has to have 8 electrons or be empty.
- you would have to put it in a zinc solution and switch the wires
- 2Ha^+ Mg -> Mg^2+ + H2
- because it cheaper and has the same effect
- so that their sculpture won’t oxidize
- An acid tends to have a sour taste, neutralize bases, reacted with most metals, and react with certain indicates to produce a color change. Bases include, ammonia and antacids. They have a bitter taste and a slippery feel, are corrosive, neutralize acids, and cause certain indicators to create color change.
- The pH of a solution is the measurement of the concentration of hydrogen in a solution.
- SO2 + H2O = H2SO3
- The ph
In the lab we did the other day we test different chemicals under a flame. Each chemical reacted differently to the fire, and created a cool color. these colors were created by the electronic structure of each chemical. Since each liquid we tested had a unique structure, they each gave off i different color. this is the same thing that happened in fireworks, each atom has a special group of electrons that give off different colors. In the experiment that we did only the metal ions had a reaction. the metal compounds are made of atoms that have nuclei.