Energy Flashcards

1
Q

What is energy

A

Energy is the ability to do work or transfer heat

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2
Q

Kinetic energy

A

energy of motion

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3
Q

Potential energy

A

the energy a motionless body has due to its position and its composition.

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4
Q

Exothermic

A

when energy leaves the system and goes out into surroundings. temperature decrease in system

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5
Q

How long does transfer of heat as energy continue?

A

until thermal equilibrium is achieved. i.e. both objects are at the same temperature.

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6
Q

System vs surrounding

A

System is being studied. Surroundings are everything around the system.

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7
Q

Endothermic

A

When energy enters the system from the surroundings. temperature of system increases.

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8
Q

Internal energy in a chemical system

A

the sum of the potential and kinetic energies inside the system. i.e. sum of energies of atoms, molecules, ions and the bonds between them. we usually measure change in internal energy. U

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9
Q

Q

A

heat absorbed or lost

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10
Q

heat enters system?

A

delta U >0 and q= +

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11
Q

heat leaves system?

A

delta U < 0 and q= -

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12
Q

does temperature change during a phase change?

A

no

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13
Q

isothermal process

A

a process where there is a change of a system but the temperature remains constant eg. phase changes

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14
Q

examples of endothermic phase changes

A

when you sweat, there’s water on your skin and heat is required for that water to evaporate. So heat is taken from your body and used to evaporate it.

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15
Q

Example of exothermic phase change

A

when muggy water condenses onto your skin, it releases energy. vapour——>water

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16
Q

Enthalpy

A

heat transferred between system and surroundings under conditions of constant pressure.

17
Q

Change in enthalpy

A

change in internal energy at constant volume

18
Q

endothermic phase changes

A

sublimation, melting/fusion, vaporisation

19
Q

exothermic phase changes

A

deposition, condensation, freezing

20
Q

First Law of Thermodynamics

A

The total internal energy of an isolated system is constant.

21
Q

state function

A

no matter which path is taken, the results are the same. eg. enthalpy

22
Q

what apparatus measures heat of combustion?

A

bomb calorimeter

23
Q

Hess’s Law

A

the overall enthalpy change of the reaction is equal to the sum of all the enthalpy changes of individual steps of the reaction.

24
Q

What is enthalpy of formation

A

the enthalpy change of a reaction when 1 mole of a compound is formed from its elements. always reported at standard conditions i.e. 1 atm and 25 degrees celcius

25
Q

Are enthalpies the same for the same compound except in different phases?

A

No, they are different according to each phase because enthalpy is a state function.