56 lines
4.5 KiB
Markdown
56 lines
4.5 KiB
Markdown
[[Chemistry of Life]]
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# SUMMARY
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## Key Takeaways
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- Water is polar because the O-H bonds are polar covalent, giving oxygen a partial negative charge and each hydrogen a partial positive charge.
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- Hydrogen bonds form between the partial positive hydrogen of one water molecule and the partial negative oxygen of a neighboring molecule.
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- Hydrogen bonding produces cohesion, adhesion, and surface tension between water molecules.
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- Water's high specific heat capacity helps organisms maintain a stable, homeostatic body temperature.
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- Water's high heat of vaporization allows [evaporative cooling](https://fiveable.me/ap-bio/key-terms/evaporative-cooling), which also helps maintain body temperature.
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- Hydrophilic substances attract water; [hydrophobic](https://fiveable.me/ap-bio/key-terms/hydrophobic) substances do not, because polarity determines what mixes with water.
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| Term | Definition |
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| ---------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| adhesion | The attractive force between water molecules and other polar substances, allowing water to stick to different surfaces. |
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| cohesion | The attractive force between water molecules that causes them to stick together, resulting from hydrogen bonding. |
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| evaporative cooling | The process by which the evaporation of water removes heat from an organism or environment. |
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| heat of vaporization | The energy required to convert a liquid to a gas, enabling water to remove heat from organisms through evaporative cooling. |
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| homeostasis | The maintenance of stable internal environmental conditions in an organism despite external and internal changes. |
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| hydrogen bond | Weak attractive forces between a hydrogen atom bonded to an electronegative atom and another electronegative atom, occurring between or within biological molecules. |
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| polar covalent bonds | Chemical bonds between atoms where electrons are unequally shared, resulting in partial positive and negative charges. |
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| polarity | The unequal distribution of electrical charge in a molecule, resulting in one end being partially positive and the other partially negative. |
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| specific heat capacity | The amount of energy required to raise the temperature of a substance by one degree, allowing water to resist rapid temperature changes. |
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| surface tension | The property of water that allows its surface to resist breaking, resulting from hydrogen bonding between adjacent water molecules. |
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# Overview
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covalents are 0-0.5 difference in electronegativities
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polar covalents are 0.5 - 2
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Ionics are 2+
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hydrogen bonds are when a hydrogen atom in one molecule is highly attracted to an atom with high electronegativity in another molecule.
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hydrogen bonds are rather weak, water uses hydrogen bonds
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**properties of water:**
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1. cohesion
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2. adhesion
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3. high heat capacity
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4. high surface tension
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adhesion is a result of the polarity, as the imbalance of charge allows the molecules to bind to other things easily
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high heat capacity results from heat energy being used to break and disrupt the hydrogen bonds, inadvertently losing some of the heat
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surface tension results from hydrogen bonds
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**ph**
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ph measures how acidic or basic a solution is
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![[Pasted image 20260810212842.png]]"**==Acids==** donate protons (Hydrogens) to **==bases==**, which are hydrogen/proton acceptors. Let’s use the self ionization of water pictured above as an example. One of the water molecules is acting as an acid and donating an H+ ion (proton) to the other water molecule, which is the base. This forms a hydronium ion (H3O+) and a hydroxide ion (OH−)."
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solutions with more hydroniums than hydroxides are acidic, and the other way
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![[Pasted image 20260810213049.png]]
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$pH=-\log[H^+]$
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where $H^+$ is the hydronium concentration in the solution
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pH has an opposite, pOH
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by definition the pH + pOH of a solution will always equal 14 |