Chemistry: Atoms First (2nd Edition)

Published by Cengage Learning
ISBN 10: 1305079248
ISBN 13: 978-1-30507-924-3

Chapter 2 - Exercises - Page 99c: 70

Answer

See the explanation

Work Step by Step

To show that the units for both forms are the same, let's first analyze the units for each term: 1. For the left side of the equation \(\Delta E \cdot \Delta t\): - \(\Delta E\) represents energy, which has units of joules (J). - \(\Delta t\) represents time, which has units of seconds (s). - Therefore, the units for \(\Delta E \cdot \Delta t\) are joules times seconds (J⋅s). 2. For the right side of the equation \(\frac{h}{4 \pi}\): - \(h\) is the Planck constant, which has units of joule-seconds (J⋅s). - \(\pi\) is a dimensionless constant. - Therefore, the units for \(\frac{h}{4 \pi}\) are also joules times seconds (J⋅s). Now, let's analyze the units for the second form: 1. For the left side of the equation \(\Delta x \cdot \Delta(mv)\): - \(\Delta x\) represents displacement, which has units of meters (m). - \(\Delta (mv)\) represents change in momentum, which has units of kilogram-meters per second (kg⋅m/s). - Therefore, the units for \(\Delta x \cdot \Delta (mv)\) are meters times kilogram-meters per second (m⋅kg⋅m/s), which simplifies to \(m^2 \cdot kg/s\). 2. For the right side of the equation \(\frac{h}{4 \pi}\): - As mentioned earlier, the units are joules times seconds (J⋅s). To show that these units are the same, we need to demonstrate that \(m^2 \cdot kg/s\) is equivalent to \(J \cdot s\). Recall that the units of momentum are \(kg \cdot m/s\), and since \(1 \, J = 1 \, kg \cdot m^2/s^2\), we can rewrite \(J\) as \(kg \cdot m^2/s^2\). So, \(J \cdot s = (kg \cdot m^2/s^2) \cdot s = kg \cdot m^2/s\), which matches the units of \(\Delta x \cdot \Delta(mv)\). Therefore, the units for both forms are indeed the same, confirming the equivalence of the two expressions of the Heisenberg uncertainty principle.
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