## Delta U = Q

$\Delta U=q+w$

Drew Myers 4G
Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

### Delta U = Q

When does delta U only equal to q (when does w = 0)?

Alex Chen 2L
Posts: 86
Joined: Wed Sep 18, 2019 12:21 am

### Re: Delta U = Q

When w = 0, it means the system has constant volume and no energy is being used for expansion/compression work. Therefore, the change in internal energy U only depends on the energy transferred through heat, q.

Matt F
Posts: 100
Joined: Sat Aug 17, 2019 12:17 am

### Re: Delta U = Q

As mentioned above, delta U will be equal to only q when work (w) is equal to zero. This can be seen in a closed system with constant volume, as work is typically done due to compression or expansion (changes in volume).

Kaitlyn Ang 1J
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Joined: Fri Aug 09, 2019 12:17 am
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### Re: Delta U = Q

Adding to this, you know work = 0 when $\Delta{V} = 0$ because $w = -P\Delta{V}$ so 0 for $\Delta{V}$ (aka there is no change in volume, aka the volume is constant) makes the entire work equation 0

Osvaldo SanchezF -1H
Posts: 122
Joined: Wed Sep 18, 2019 12:21 am

### Re: Delta U = Q

When there is no expansion or compression, then the system is doing no work or no work is being done on the system so therefore Work would equal to 0. This means that Delta H would only be impacted by (+/-)q.

Sydney Myers 4I
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Joined: Fri Aug 09, 2019 12:17 am

### Re: Delta U = Q

Kaitlyn Ang 1J wrote:Adding to this, you know work = 0 when $\Delta{V} = 0$ because $w = -P\Delta{V}$ so 0 for $\Delta{V}$ (aka there is no change in volume, aka the volume is constant) makes the entire work equation 0

expanding on this, work is also 0 when pressure is 0, or when the system is in a vacuum.

MeeraBhagat
Posts: 95
Joined: Sat Aug 24, 2019 12:15 am

### Re: Delta U = Q

Work=0 when volume is not changing or when pressure is zero (vacuum).

Hannah Pham
Posts: 104
Joined: Fri Aug 09, 2019 12:17 am

### Re: Delta U = Q

When W = 0 there is constant volume, in which there is no expansion or compression because that is when work is done.

Abigail_Hagen2G
Posts: 107
Joined: Fri Aug 09, 2019 12:17 am

### Re: Delta U = Q

The work is zero when there is no expansion in volume or change in pressure, because otherwise it would affect the internal energy.