Phase of the chirp signal
Take the chirp signal

$$
x(t) = e^{j\pi\alpha t^2} = e^{j\phi(t)}
$$

Where $\alpha$ is the chirp rate of the signal. You can see that the function describing the phase, $\phi(t)$, is in the form of a quadratic equation. So you can plot

$$
\phi(t) = \pi\alpha t^2
$$

and see the quadratic nature of the phase at any point in time. The actual phase-change between each sample depends on what your sample rate is.