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bioChem1100.tri-c
Chap6.energy
| Question | Answer |
|---|---|
| energy | defined at the ability to do work |
| potential energy | stored energy; gasoline in a tank |
| kinetic energy | energy of motion - water going over a dam is kinetic energy |
| heat | Energy associated with the motion of particles in a substance |
| Joule (J) | Scientific unit of enery & work - kilojoule used more often (joule is very small) Ex. heating water for tea uses 75,000 J or 75kJ of heat |
| Calorie | Latin "caloric" meaning heat - originally defined as the amount of energy need to rasie the temp. of one gram of water by 1 degree Centigrade |
| 1 calorie equals _____ Joules | 1 cal =4.184 J |
| activation energy | the energy needed to break the bonds of reacting molecules |
| What is needed for chemical reaction to take place? | The molecules of the reactants must come in contact--collide, break bonds & make new bonds |
| Heat of reaction | Heat of reaction is amount of heat absorbed or release during a reaction that takes place at constant pressure |
| Heat of reaction (equation) | (temp sign - triangle) = Hproducts minus H reactants |
| Endothermic reaction | Ex. (lab) when table salt NaCL dissolves in water, energy to break the ionic bonds between the Na+ and the Cl- is needed; the energy comes from the water and can be measured by a drop in temperature |
| Endothermic reaction - another example | Rock salt is added to the water/ice used to make ice cream because the rock salt will rob the water of its heat as it break down into Na+ and Cl- |
| Exothermic | a reaction that gives off heat Ex. "heat packs" use the heat given off by rusting iron |
| endothermic reaction - is the energy greater with the reactants or the products? | Endothermic - Energy of the products is greater-the products have absorbed the energy - ex. Water plus heat equals gas |
| Endothermic - what does curve of reaction look like? | curve of reactants starts low, activation energy climbs, then curve is slightly down--but energy is absorbed by products, so curve is higher at end |
| Exothermic reaction | Curve of reaction starts high, activation energy is reached, then heat is released, so that energy curve is lower at the end |
| specific heat | A quantity of heat that changes the temperature of exactly 1 g of a substance by exactly 1 degree Centigrade |
| Specific heat | Refers to the fact that every substance has it own characteristic ability to absorb heat |
| Specific heat (equation) | Specific heat (SH) = heat/grams x delta Temperature = calories (or joules)/ 1 gram x 1 degree Centigrad |
| Rate these by Specific heat: water, aluminum, ammonia, copper | Aluminum (lowest), copper, ammonia, water |
| Water has a high specific heat, therefore | water requires MORE energy to bring it up by 1 degree C; therefore the body can use its water to absorb or release heat to maintain constant temperature |
| Heat equation | Use the value of the specific heat of a substance to calculate heat lost or gained during a reaction |
| Heat equation - Ex. | Heat = mass x temperature change x specific heat |
| 1 Calorie (with a capital C) equal | 1000 calories; 1 Calorie is actually a kilocalorie |
| Calorimeter | Device surrounded by water which burns food substances and records the heat released during the burn; this is calculated to determine the caloric content of the food |
| Caloric value: carbohydrates | 4 kcal per 1 gram of carbohydrate |
| Caloric value - fat (lipid) | 9 kcal per 1 gram of fat |
| Caloric value - protein | 4 kcal per 1 gram of fat |
| 4 - 9 - 4 | carbos - fats - protein "carbo 54 where are you?" (4 , the 4 &5 make 9, then 4 again) |
| How many kilocalories in cake w/35 g of carbohydrate, 10 g of fat & 5 g of protein? Equation | 35 g x 4kcal/1 g; then 10 g x 9 kcal/1 gram ; then 5 g x 4 kcal/1 g |
| Equation for caloric value | Multiply # of grams (fat, etc) by standard 4 kcal/1 g then add up values |
| Matter | Anything that occupies space and has mass |
| Solid (matter) 4 characteristics | a state of matter that has its own shape and volume - definite shape may be a crystal |
| Liquid | A state of matter that takes the shape of its container by has a definite volume |
| Gas | A state of matter characterized by no definite shape or volume. Particles in gas move rapidly |
| boiling | the formation of bubbles of gas throughout a liquid |
| Dipole-dipole attraction | attractive forces in molecules occur bewtween the positive end of one molecul and negative end of another |
| Hydrogen bond | Attractive force between partially positive hydorgen atom & the strongly enlectronegative atoms F, O or N - major factor in biological molecules, DNA |
| Dispersion forces | weak dipole bonding that still enables some substances to form temporary bonds |
| Ionic bond | Ex. NaCL - between atoms - a metal & nonmetal - very strong |
| Change of state - matter | matter is converted from one state to another |
| Melting point | the temperature at which a solid becomes a lliquid (melts) it is the same temperature as the freezing point |
| Freezing point is the ______ as the melting point | Freezing point is the same temperature as the freezing point |
| Heat of fusion | during melting energy called the heat of fusion is needed to separate the particles of a solid |
| Calculate heat of fusion (equation) | heat = mass x heat of fusion |
| sublimation | solid changes directly to gas |
| What is sbublimation useful? | Because freeze-dried foods do not need refrigeration because bacteria cannot grow without moisture |
| Deposition | Gas changes directly to solid |
| Evaporation | Water molecules escape from the liquid surface and enter the gas phase |
| Boiling point (bp) | All the molecules have the energy needed to change into gas |
| Boiling | Boiling of a liquid occurs as gas bubbles form throughout the liquid, then rise to surface and escape |
| Condensation - | Water changes from vapor (gas) back to liquid form |
| Heat of vaporization | Energy needed to vaporize 1 g of liquid to gas at its boiling point |
| Heating and Cooling Curves | Diagram used to illustrate changes of state |
| On a cooling curve, what does the plateau at 100 degrees centigrade represent? | (blank) |
Created by:
walterina4327