Show:
Exo- or Endo-?
Kinetic or potential?
Chem. reaction
Q =?
Etc.
100
Exothermic or endothermic? COMBUSTION
Exothermic
100
Kinetic energy is energy of __________ and potential energy is _________ energy.
motion; stored
100
What is another word for "combustion?"
Fire/burning
100
What is the formula for Q, or thermal energy?
Q = m c deltaT
100
Name two fuels we tested in our "Comparing Fuels" lab.
Paraffin oil, paraffin wax, ethyl alcohol, methyl alcohol, methane, butane
200
"Exo" means ___________ and "endo" means ______.
"Exo" means OUT and "endo" means IN.
200
Is the energy that is stored in chemical bonds considered potential or kinetic energy?
Potential energy
200
Give three examples of combustion.
Answers will vary. Anything burning.
200
What does "thermal energy" mean, and what are the units we measure it in?
Thermal energy = heat. It is measured in JOULES.
200
You burned some popcorn. Oops! Was it an exothermic or an endothermic reaction?
Burning, or combusting, ANYTHING is always an exothermic reaction. It give OUT HEAT.
300
Give an example of an endothermic process.
Baking soda and vinegar reacting and getting cold, ice melting, a cold pack reacting and getting cold, etc. Anything that takes IN HEAT. (Which therefore FEELS COLD to you.)
300
Which of the following demonstrate potential energy? A car at the top of a hill, a car rolling down the hill, gasoline in the car's tank, the battery in the car's engine.
All except the car rolling down the hill. A car rolling is demonstrating kinetic energy, or energy of movement.
300
Write the equation on the board for the combustion of a fuel. Include energy.
Fuel and oxygen form carbon dioxide, water, and energy.
300
During the candle burning lab, how did you calculate "m" in the equation m c delta T?
"m" was the mass of the water.
300
What are the reactants in a combustion equation?
fuel and oxygen
400
Is fossil formation exothermic or endothermic? Explain.
Endothermic. Plants take IN energy from the sun, and this energy is stored in the bonds of the chemicals formed in plants/fossil fuels.
400
Give an example in which the energy of the sun has actually ended up inside a molecule on earth.
Photosynthesis: plants convert sunlight to the energy in the bonds of chemicals. Fossil fuel formation: same as above, except those plants got buried for millions of years.
400
Write the equation on the board for the combustion of methane (CH4) on the board. Include energy. Balance the equation.
CH4 + 2 O2 forms CO2 + 2H2O.
400
Calculate the thermal energy, or Q, for a flame that heats up 1 gram of water 10 degrees. Get the unit correct!
m c delta T: 1 gram x 4.2 x 10 degrees = 42 Joules.
400
What are two things you kept CONSTANT in your comparing fuels lab?
Time, volume of water, distance from flame to bottom of can
500
During ONE chemical reaction, chemical bonds are broken and re-formed. Since the breaking of bonds takes energy and the formation of bonds releases energy, what determines if the OVERALL reaction is endothermic or exothermic?
Add up how much energy is taken in and how much energy is given off. If more energy is given off than taken in, the reaction is exothermic. If more energy is taken in than given off, the reaction is endothermic.
500
Draw a potential energy diagram for the digestion of a potato chip in your body.
When you digest a potato chip, you are releasing energy stored in the bonds of the potato (and the grease!!), so it is exothermic. A diagram showing the lowering of the energy should be drawn, since energy is given off.
500
Write the equation on the board for the formation (not combustion) of the fossil fuel gasoline (C8H18). Include energy. You do not need to balance it.
The formation of fossil fuels is opposite of the burning of fossil fuels. So flip around the equation for combustion and you get: CO2 + H2O + energy from the sun forms C8H18 and O2.
500
When the wax in your candle burned, it seemed to disappear. Since we know matter can't disappear, what happened to it? HINT: it didn't "evaporate."
The carbon and hydrogen in the wax combined with oxygen in the air to form carbon dioxide and water, which then went into the air.
500
Which will release more energy when you burn it: methane or butane? Explain.
Since butane has a lot more chemical bonds in it, it has stored a lot more energy. So, when you burn it, it will give off more energy.