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2,3 (types of chemical bonds (weak bonds can temporarily happen when two…
2,3
types of chemical bonds
atoms share or transfer valence electrons, resulting in the atom staying together held by attractions called chemical bonds
strongest kind
covalent bond
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covalent, sharing of a pair of valence electrons by two atoms
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single bond can be represented in a structural formula, ex:H-H the line being the pair of shared electrons
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nonpolar covalent bond
electrons that are shared equally b/c the atoms have the same electronegativity (H2, and O2)
polar covalent bond
an atom is bonded to another atom that is more electronegative, the electrons of that bond do not get shared equally
ionic bonds
cations are positively charged, and anions are negatively charged
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anions, negatively charged atom
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evaporative cooling
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ex: glass of water at room temp, liquid being heated
heat of evaporation. heat of a liquid must absorb one gram to be converted from the liquid to gaseous state
b/c waters high heat of vaporization results from the strength of hydrogen bonds, that need to be broken before a molecule can leave a liquid in the form of water vapor
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evaporative cooling occurs b/c the hotter molecules the ones with greater kinetic energy, leave as a gas
ex: cooling of water stabilizes temp of lakes, ponds, and prevents from terrestrial organism from overheating
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temperature and heat
kinetic energy, energy of motion
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thermal energy, the random movement of the atoms and or molecules is associated with kinetic energy
temperature, the average kinetic energy of molecules in a body of matter.
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water: solvent of life
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aqueous solution, the solute is dissolved in water, water is the solvent
water is a versatile solvent, traceable to the polarity of the water molecule
compound does not need to be ionic to dissolve in water, compounds made up of nonionic polar molecules are water soluble
they dissolve when water molecules surround the solute molecules which then hydrogen bonds are formed with them
structure of atoms
atom, the smallest unit of matter that retains properties of an element
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acids and bases
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base, substances reduces hydrogen ion concentration of a solution (ex : ammonia acts as a base)
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pH scale
neutral aqueous solution at 25C is 7, pH less than 7 is an acidic solution, (lower number the more acidic), pH of basic is above7. And biological fluids range of pH 6-8
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Buffers,
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pH for internal cells is around 7, if the pH is changes even slightly it can be harmful b/c chemical processes of a cell are sensitive to a concentration of hydrogen and hydroxide ions
pH for human blood around 7.4 (basic), a person will not survive if blood pH goes down to 7 and or rises to 7.8 which is why there is chemical system in the blood to help maintain a stable pH
elements and compounds
element, can not be broken down to other substances by chemical changes
compounds, a substance of two or more elements that are combines in a fixed ratio
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types of elements
essential elements,(20-25%) are what organisms need for a healthy life and to reproduce
carbon, hydrogen, nitrogen, oxygen make up 96% of living matter
trace elements, are required by an organism in minute quantities
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Chemical reactions
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writing a reaction, arrows are used to show conversion. reactants to the products
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reaction can neither destroy or create atoms, but it can rearrange its electrons
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chemical reactions are reversible, so that the products become the reactant for the reverse reaction
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hydrophilic, substance with an affinity for water
ex: cotton, partial negative partial positive charges allowing it to form hydrogen bonds
hydrophobic , substance that do not have an affinity for water
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