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Enthalpy
Enthalpy
The energy stored in the chemical bonds is known as chemical potential energy. During chemical reactions these bonds break apart and new bonds are formed which can cause energy to be gained or lost by the system. Each bond has its own energy within it and we can use this energy to determine if a reaction is endothermic or exothermic.
When writing a chemical equation with an energy change we can either write the specific amounts of energy absorbed or released or use a Δ symbol over the arrow in the equation to denote heat.
When we look at energy terms in chemical equations sometimes they are placed to the side of the reaction instead. The negative energy means that the reaction is exothermic! The first one is for creating 1 mole of H2O while the scaled up version is how you'd generally see it as a balanced chemical equation.
Since we know that energy gained and released in reactions are used to make and break bonds we can also combine chemical equations together using math to figure out how much energy would be gained or released for unknown reactions. This is known as Hess' Law, and it works just like solving systems of equations in math.
Taking 3 balanced equations and their energy terms and adding them together gives us a new formula and new amount of energy transfer! Most terms should cancel out, leaving the ones that we have for the final reaction.
Activation Energy
Activation Energy
Reactions generally need a specific amount of energy for a reaction to even happen since particles colliding need to be able to break apart and rearrange. The energy required for this to happen is known as activation energy. Once a reaction hits this point, it's considered an activated complex when the bonds of its reactants break and rearrange, then quickly transforms into product.
Sometimes the product that's being formed will quickly go on to create other products if the amount of energy required for it to further react is available. In this case the substance it transformed into is known as a reaction intermediate.
Vinegar (HC2H3O2) and Baking Soda (NaHCO3) reacting is a multistep reaction! After double displacement the carbonic acid breaks down since its activation energy is low enough, forming carbon dioxide and water.
Calorimetry
Calorimetry
When something changes in energy, we can use what is known as a Calorimeter to know exactly how much energy was absorbed or released. This uses the specific heat formula for water (since water is what ends up heating up in the calorimeter when the reaction occurs).
Calories = mass of water x 4.190 x Temp Change
We can use this process for many things, such as to determine the calories in food, the energy stored in fuel, how much energy something absorbs while melting, and more.
Electrochemistry
Electrochemistry
Batteries use chemical processes to produce electrical energy, making it through chemicals moving or reacting in such a way that their electrons move thorough a wire while chemicals that make it up move through a membrane as a positively charged ion. There are always two sides of a battery, with electrons flowing from the anode side to the cathode side (think anions and cations for how this electricity moves - since electrons are negative they leave the anode and are attracted to the cathode). Fuel cells and solar panels also work in similar ways.
Electrons travel through objects as electricity, a form of kinetic energy. How fast these electrons are moving is also known as Power, which is measured in Watts (W).
Having a complete electric circuit creates an electric current and allows electrons to flow!
Additional Resources
Additional Resources
Interesting Links
Interesting Links
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