# First Law of Thermodynamics

#### Sixty3

1. Homework Statement
I am looking into the first law of thermodynamics.
But I'm not sure with some parts.

2. Homework Equations
dU=Q-W What does it mean when U Q and W are negatives.
Also solids with W=0

3. The Attempt at a Solution
So the equation will change to -U=-Q+W
Does it lose it's internal energy?

Last edited:
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#### willem2

It's

$$dU = \delta Q - \delta W$$

If dU is negative that means that the system loses internal energy. The temperature goes down, or water freezing etc.

if $\delta Q$ is negative, the system supplies heat to its surroundings.

if $\delta W$ is negative, the system does negative work on its surroundings, this is the same as positive work done on the system

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