How far has a black hole to be in order for its tidal forces to disintegrate earth? I don't know if this question can be answered to honest but I though I might try ask just in case someone can calculate that.
What I need to know here is how strong should the tidal forces be to start separating chunks of earth and therefore determine how far this force can be from a black hole.
My assumption here is a 10 solar masses black hole.  
 A: The distance at which the tidal forces froma  primary start tearing apart a satellite is known as the Roche limit. In calculating the Roche limit we assume that the yield stress of the rock making up the planet is small compared to the gravitational forces at work so it can be ignored. The question is then simply whether the gravity of the body (in this case the Earth) is stronger than the tidal forces trying to pull it apart. This makes the calculation fairly simple, and as I calculated in Roche Limits and black holes the equation for the Roche limit in terms of the primary mass $M$ is:
$$
\begin{align}
 d &= \left( 2 \frac{\frac{3M}{4\pi}}{\rho} \right) ^{1/3} \tag{1}
\end{align}$$
where $\rho$ is the density of the satellite. The Earth doesn't have a uniform density so the calculation is going to be rather rough, but we can use the average density, which is $5514$ kg/m$^3$. Ten solar masses is $1.99 \times 10^{31}$ kg, and feeding these values into equation (1) we get:
$$ d \approx 1.2 \times 10^9 \text{m} $$
For comparison this is about 0.8% of the distance from the Earth to the Sun.
Given the approximations involved in calculating this you should regard it as an order of magnitude estimate. In any case the destruction of the earth would be progressive. First the atmosphere would be torn off, then the seas and then the mantle. The iron core would be the last to go.
One last comment, you ask about a ten solar mass black hole, but the body doesn't need to be a black hole. The event horizon of a ten solar mass black hole would be about 30,000m so the earth would be torn apart well before it got anywhere near the event horizon. A ten solar mass neutron star would be just as destructive.
