Question

you have a mixture made of two substances one with a higher density than the other how could you separate the substances in the mixture

Answer 1

depends

gravity is your friend

oil and water separate quite naturally

but are they fluids??

Answer 2

if they are fluids, you can use a separatory funnel
it is a modified funnel that has a tap
so you open the tap and the fluid with higher density falls down and as the less denser fluid's bottom surface touches the tap, you shouldclose the tap
The written answer may not be very clear but, you'll get it from the figure