Term
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Definition
| Energy is the ability or capacity to do work. Ex: Moving molecules across a concentration gradient Ex: Synthesize/decompose molecules through dehydration/hydrolysis. Need energy to do anything. |
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Term
| What are the types of energy and where are they found? |
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Definition
| There is Kinetic energy (motion) and there is potential energy (stored). There is also thermal, mechanical and chemical energy. Chemical energy is found locked in bonds like NaCl. Ex: Stand up on a chair, while standing potential (stored) energy gathers so when you go down, it converts to kinetic energy (motion) to be used. |
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Term
| What is the unit of measurement for energy? |
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Definition
| Energy is measured in Joules and in calories. Usually kJ are used because 1 Joule = 0.239 calorie so kJ are closer to the calorie amount of energy. |
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Term
| What is the 1st law of thermodynamics? |
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Definition
| The first law of thermodynamics is that energy in a closed system is ALWAYS conserved. Energy cannot be destroyed nor created, it can convert into different forms. |
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Term
| Use an example to explain the first law and give the equation. |
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Definition
| The example for the first law is that a leaf accepts energy from the sun. The sun's light energy enters the leaf to create a glucose molecule. However, not all the energy is used so it turns into thermal energy and leaves. So, energy stored (glucose) = Energy in (sunlight energy) - Energy out (thermal) |
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Term
| What is enthalpy and what types of reactions does it entail? |
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Definition
| Enthalpy is abbreviated with the letter H. It is the amount of heat absorbed or released in a chemical reaction under a constant pressure. The types of reactions that occur are exothermic (release of heat) and endothermic (absoprtion of heat). |
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Term
| Explain how cellular respiration works in relation to enthalpy. |
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Definition
| Cellular respiration is an exothermic reaction. Its reactants (C6H12O6 + 6O2) turn into the products: 6CO2 + 6 H2O. After the activation energy and the transition state are surpassed, the potential energy decreases. So, the change in enthalpy is negative (-2870 kJ/mol) so the reaction is exothermic: heat was released. |
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Term
| Explain how photosynthesis works in relation to enthalpy. |
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Definition
| Photosynthesis has the reactants: 6CO2 + 6H2O and the products C6H12O6 + 6O2. After the transition state and the activation energy is surpassed, the potential energy increases. So, the change in enthalpy is positive (2870 kJ/mol) and the reaction is endothermic: heat was absorbed. |
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Term
| What is the second law of thermodynamics? |
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Definition
| The second law os thermodynamics is that Entropy (S) indicates that disorder or chaos is favoured in the universe. **In the universe, not a closed system like in the first law** |
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Term
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Definition
| Entropy is increased by making large molecules into many smaller ones, decreasing pressure so there's more room for chaos, increasing volume like the semi-permeable membrane lab, changing state (like adding heat to ice and water) and inceasing temperature. |
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Term
| What does escaped energy have to do with entropy? |
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Definition
| Any reaction that involves escaped energy (like the thermal energy in the leaf example), leaves to help the production of other molecules to increase entropy. |
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Term
| Explain how photosynthesis does NOT goes against entropy. |
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Definition
| Photosynthesis does go against entropy in some ways. Its reaction involves turning smaller molecules into bigger ones, which goes against the ideals of chaos and disorder because it creates more order by creating glucose. However, thermal energy is constantly released (like in the leaf example) which causes chaos to increase entropy. |
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Term
| What is a favoured reaction and give some examples? |
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Definition
| A favoured reaction is a spontaneous one. Spontaneous reactions continue on their own once they are started. Ex: Lighting a match: dragging = initial input but once it starts to burn, it goes on its own. Ex: Boiling water, it is not spontaneous because once you no longer apply heat to it, it stops boiling, so it is controlled. |
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Term
| What is Gibbs Free Energy and what is the equation? |
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Definition
| Gibbs Free Energy (G) tells you the amount of useful energy created by a reaction. The equation is G = H - (T)(S) which is Gibbs Free Energy = Enthalpy - (temperature)(Entropy). It takes into account the 2 laws and tells you if a reaction is favoured. |
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Term
| If a reaction is favoured, what does that mean? |
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Definition
| If a reaction is favoured, the change in Gibbs Free energy will be negative, meaning the reaction is spontaneous, exothermic (releases energy) and increases entropy. |
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Term
| If a reaction is not favoured, what does that mean? |
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Definition
| If a reaction is not favoured, that means that the change in Gibbs Free energy is positive, meaning the reaction is not spontaneous, endothermic and decreases entropy. |
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Term
| What is tricky about the temperature in the equation? |
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Definition
| All other reaction combinations require analysis of the temperature (higher temperature can make the Gibbs Free energy negative, but at a lower temperature, it would make the Gibbs Free Energy positive). It changes how the reaction affects entropy. |
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Term
| Use the hydrolysis of ATP to explain change in Gibbs Free Energy. |
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Definition
| ATP breaks down to ADP after surpassing the transition state and the activation energy. The potential energy then decreases to make the products ADP + Pi. So, the Gibbs Free Energy is negative (-31 kJ/mol) so the reaction is favoured, and it is exergonic because the energy is to be used elsewhere. |
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Term
| Use the dehydration of ADP to ATP to explain Gibbs Free Energy. |
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Definition
| ADP + Pi dehydrate to form ATP. After surpassing the transition state and activation energy, the potential energy has increased. So, the Gibbs Free Energy is positive (31 kJ/mol) and the reaction is endergonic (requires energy). The reaction is not favoured, so it is not spontaneous and decreases entropy. |
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Term
| What is the common myth associated with positive Gibbs Free Energy reactions that go against entropy? |
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Definition
| The common myth is that because they go against entropy, they will not continue on their own but it just needs constant energy so it will happen even though it is not favoured. |
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Term
| What is the difference between change in Enthalpy and change in Gibbs Free Energy? |
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Definition
| Enthalpy is heat and Gibbs Free energy is useful energy. The Gibbs Free will always be a little less than what the enthalpy is. |
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Term
| What are redox reactions? |
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Definition
| Redox reactions are reductions (gain of electrons, H or loss of oxygen) and oxidations (loss of electrons, H or gain of oxygen). |
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Term
| What is the anagram for redox reactions? |
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Definition
| LEO says GER. LEO = loss of electrons, oxidation GER = gain of electrons, reduction |
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Term
| Explain the reaction CH4 + 2O2 -> CO2 + 2H2O using redox reactions. |
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Definition
| CH4 is being oxidized because it is losing electrons and gaining oxygen, turning into CO2. 2O2 is being reduced, gaining electrons and H, turning into 2H2O. In this case, because CH4 is being oxidized, it is the reducing agent. 2O2 is being reduced so it is the oxidizing agent. |
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Term
| Explain oxidizing and reducing agents. |
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Definition
| Oxidizing agents accept e-/H, so they get reduced. Reducing agents donate e-/H, so they get oxidized. **It is always the opposite** |
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Term
| Explain coupled reactions. |
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Definition
reducing agent:
donates e-, gets oxidized
Na Cl
> <
Na+ Cl-
oxidized: loss of e- reduced: gain of e- |
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