Answer:
Energy
Explanation:
Paper is oxidized in the presence of oxygen. This reaction however proceeds very slowly until energy is supplied to the system. This implies that the reaction is not spontaneous at room temperature. A spontaneous reaction takes place without any need for external supply of energy.
The need for supply of external energy must be as a result of the high activation energy required for the reaction to go to completion. If a chemical reaction has a high activation energy, it will require an external supply of energy in order for such reaction to occur.
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4.) Heat is transferred through a piece of metal by _____.
conduction
Conduction happens when both items are in close contact. In a piece of metal. In this case, the heat transfers gradually into the other ends of the object. This makes the transfer rate is slow on a long object with a low surface area.
5.) Heat from the sun travels to earth by _____.
radiation
</span>Sun energy comes from a reaction that will produce a light and heat and it is transferred to the earth by radiation. While conduction and convection need contact with the object, radiation doesn't. Radiation can travels a very long distance, that is why the heat could be delivered to the earth.
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6.) Energy in a vacuum travels by ___.
radiation
</span>One of the examples for energy travels in a vacuum would be sunlight. Sun and earth are separated by vacuum space which means there is no direct contact between earth and sun. That means conduction and convection are not possible.
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7.) In a convection current _____.
</span><span>C.)cool fluid is more dense, and therefore, sinks
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Cool fluid have lower volume, thus become denser than warm fluid. Since its density higher than the warm fluid, it will sinks and moves toward the earth. The warm fluid also rises to replace the cool fluid.
8.) Nuclear reactions occurring in the Sun _____. Select all that apply.
generate light
generate heat
fuse atoms of hydrogen to make helium atoms
Sun is bright and hot, which means it produces light and heat. The reaction should be producing energy, not absorbing energy. The reaction that produces that energy would be the fusion reaction of hydrogen into helium.
9.) Which of the following statements is true?
</span><span>C.)The sun's energy comes from the nuclear reactions of changing hydrogen into helium.
</span><span>The sun reaction is right, it is forming helium using hydrogens.
Transfer of heat in liquid mostly happens because convection which need direct contact. But the heat can transfer by radiation too, so its a bit ambiguous.
Temperature represents the average kinetic energy of the molecule and it is different with heat/thermal energy.</span>
The differences are <u>the number of neutrons</u> and the <u>atomic mass</u><u /><u />.
Copper-63 has an atomic mass of 63 amu, and has 34 neutrons.
Copper-65 has an atomic mass of 65 amu, and has 36 neutrons.
