A magnet
I don't
Sand, marbles, and water can be a mixture.
Their physical properties
You can evaporate the water from the sugar.
No, it's heterogeneous.
I don't
Because you can separate seashells and marbles with your hands and you can't with copper sulfate
when you separate a substance from a mixture, it's a physical change... Technically, you can get it back in the mixture.
You depend on the physical state of the constituents to separate a mixture
Sand, marbles, and water can be a mixture.
Filtration, evaporation, chromatography, and distillation are some physical processes to separate a mixture.
It depends on what is in the mixture. If it's cake batter with flour, sugar, salt, butter, etc. then yeh it's basically impossible. But if it's a mixture of marbles and sand then you can easily separate those.
Their physical properties
yes
yes
It is a heterogeneous mixture because you can distinguish between the different colored marbles. The mixture is not the same throughout.
it's a mixture !