First Law of Thermodynamics

Conservation of Energy

Concept: First Law of Thermodynamics Intro

1m

Concept: First Law of Thermodynamics Concept

6m

First Law of Thermodynamics Additional Practice Problems

Select the correct statement of the first law of thermodynamics. 

a) At a temperature of 0 K the entropy of a pure crystalline solid is

b) In a spontaneous process, the entropy of the universe increases

c) Energy is conserved, or, mathematically, delta E = q + w

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On what law is the first law of thermodynamics based? Explain the sign conventions in the equation ΔU = q + w.

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Stoichiometry is based on the law of conservation of mass. On what law is thermochemistry based?

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A truck initially traveling at 60 km per hour is brought to a complete stop at a traffic light. Does this change violate the law of conservation of energy? Explain.

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Which statement would be the best interpretation of the First Law of Thermodynamics?

1. The total amount of energy in the universe is increasing.

2. The total amount of energy in the universe is constant. 

3. The total amount of matter in the universe is constant.

4. The total amount of entropy in the universe is increasing.

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Which statement(s) is/are true regarding the first law of thermodynamics?

I) Energy can be converted from one form to another, but the total amount of energy is always conserved.

II) The first law of thermodynamics defines entropy.

III) The internal energy of the system and surroundings could both increase.

 

A) I only

B) III only

C) both II and III

D) both I and III

E) all are true

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What is the first law of thermodynamics? (circle one)

The energy of the universe is conserved.

The speed of a spontaneous process is determined by the activation energy.

Mass and energy of the universe is conserved.

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The ____ law of thermodynamic states the energy is conserved in chemical processes.

  1. Second
  2. First
  3. Third
  4. Zero
  5. None of the above
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The First Law of Thermodynamics tells us that: 

a. energy must be transferred during a chemical reaction.

b. enthalpies of formation for elements must be zero.

c. all collisions of gas molecules are elastic.

d. if something loses energy, something else must gain that same amount of energy.

e. heat always flows from a hot body to a cold body.

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