The first law of thermodynamics can be represented by the expression:$∆U=q+W.$
An ideal gas is compressed at constant temperature. 
Which row shows whether$∆U\mathit{,}\mathit{ }q$ and $W$ are negative, positive or zero during the change? 

 

What is the internal energy of an object? 

 

Describe the changes to the kinetic energy, the potential energy and the total internal energy of its molecules as ice melts into water.

Ice melts at $0°\mathrm{C}$.

 

Describe the changes to the kinetic energy, the potential energy and the total internal energy of the molecules of a block of ice as: 

The temperature of the water rises from $0°\mathrm{C}$to room temperature. 

The so-called 'zeroth law of thermodynamics' states that if the temperature of body $\mathrm{A}$ is equal to the temperature of body $\mathrm{B}$ and 

the temperature of body $\mathrm{B}$ is the same as body $\mathrm{C}$, then the temperature of body $\mathrm{C}$ equals the temperature of body $\mathrm{A}.$ 
Explain, in terms of energy flow, why the concept of temperature would be meaningless if this law was not obeyed.

. Figure shows a fixed mass of gas that undergoes a change from $\mathrm{A}$ to $\mathrm{B}$ and then to $\mathrm{C}.$

 During the change from$\mathrm{A}$ to$\mathrm{B}, 220 \mathrm{J}$of thermal energy (heat) is removed from the gas. Calculate the change in the internal energy of the gas.