Chemistry Blog #5

The main idea that we have been focusing on this week in chemistry was energy. The first thing we focused on was creating energy bar graphs. The energy bar graphs has 3 bars in it, the E(th) which is the temperature and the E(ph) which is the phase and the E(ch) which is the chemical aspect. Theres 2 graphs, initial and final, and also the energy flow which shows if the energy is flowing in or out of the object that is changing. For this energy bar graph, the water starts as liquid and it starts as room temperature. Then, it freezes, goes down to -8 degrees celsius and becomes a solid. Because when something becomes a solid and gets colder, it looses energy due to the fact that the particles are slowing down and that theres less space for the particles to move around in so they can't move as freely.

For this energy bar graph, the soda starts cold and as a liquid, and stays a liquid but becomes room temperature. The energy flow is directed inwards. This is because as the soda warms up, the particles speed up and create a higher energy, so energy is added when the soda becomes room temperature. For a energy bar where something is turning into a gas, the energy flow would also be going in because when something becomes a gas, the particles speed up so much they break away from each other. For something to become a gas it has to become really hot so the particles speed up a lot and that creates a higher energy. The second thing we were focusing on is quantitive energy problems. One of the first things we learned is that energy is a substance like quantity that is always involved whenever a system undergoes change, such as hotter to colder, faster to slower, or higher to lower. Energy is stored and transferred in different ways but it never comes in different forms. Heat is a way to transfer energy but an object doesn't store heat. Heating a system increases its thermal energy by a process of energy transfer through particle collisions. Temperature is a way to assign a numerical value to thermal energy, but temperature and energy aren't the same. As temperature increases, particles move faster and faster, so at some temperature, the particles are moving so rapidly that they can no longer maintain the arrangement of a solid, so they break free into the shape of a liquid. Then, as the temperature keeps increasing, the same things happen and particles break free into a gas phase. The flat region of a heating curve is where the phase change is happening. When you look closer at the phase change region, you can see that it is rigid, moving up and down at very small amounts. This is because when energy enters the thermal account, it raises the temperature and then the energy is immediately transferred to the phase account , which lowers the temperature. Now for the quantitive energy problems.  These let us know how much energy is transferred during these changes. We can do this by the equation Q= mc(change in temperature). Q is the amount of energy transferred, m is the mass, c is the specific heat. and change in temperature is the difference between the initial and final temperatures. That is the equation to figure out how much energy is transferred when the substance is heating or cooling. There are other equations for when a substance is freezing or melting, which is Q= (change in mass)H(f) , where H is the energy constant and (f) is for fusion. For when a substance is vaporizing or condensing, the equation is Q=(change in mass)H(v), where H is the energy constant and (v) is the for vaporizing.