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Transcript of Energy
Change in Energy
Every change in matter involves a change in energy
evaporation- occurs with an increased input of energy
many chemical changes also require an input of energy or release energy
Endothermic and Exothermic
endothermic- change in matter when energy is absorbed (ex. reaction of barium hydroxide and ammonium nitrate)
exothermic- change in matter when energy is released (ex. formation of water)
law of conservation of energy
Energy is transferred
System- all the parts of a chemical reaction that are being studied
Surroundings- air, beaker, etc.
energy exists in many forms: chemical, mechanical, light, heat, electrical, sound
Heat- energy transferred between objects and different temperatures, from warmer to cooler object
- ammonium nitrate stored chemical energy and ignited to release great amount of heat and energy as an exothermic reaction
kinetic energy- energy of an object that is in motion
Heat is Different From Temperature
baking is endothermic- sodium bicarbonate absorbs heat and breaks down into sodium carbonate, water vapor, and CO2
Temperature- measurement of how hot/cold, quantity
Celsius- 0 is freezing point of water
Kelvin- 0 is least amount of kinetic energy
C -> K = + 273, K -> C = - 273
Transfer of Heat
Transfer of heat does not always affect temp.
Add ice to cold water, ice will melt, but temp. might remain at zero degrees.
specific heat- amount of heat required to raise a unit of mass by 1K or 1 degree C.
Energy and Change
energy- involved in moving an object, forming a new compound, or generating light
Physical Change- such as change of state
Chemical Change- reaction of hydrogen and oxygen to produce water
Why is the reaction of hydrogen and oxygen to produce water a chemical reaction? You start with hydrogen and oxygen and end with hydrogen and oxygen. How can you tell that the change is chemical?
Think about it...
How can water undergo an endothermic change and how can water undergo an exothermic change?
Water = 4.186 J/gxK
Restate the law of conservation of energy in your own words.
How is heat different from temperature?
Convert 84 degrees C to degrees Kelvin and convert 200 degrees K to Celsius.
Should have stated somehow that energy is neither gained nor lost in a chemical reaction.
Heat is the transfer of energy between objects at different temperatures. Temperature is the measure of the average kinetic energy of particles in a system.
357 K and -73 degrees C
1. 25 degrees C to K
2. 300 K to C
3. 37 degrees C (normal body temp. to K
4. 150 K to C