Brushing teeth with baking powder makes it white. is this true?

Minimally: This may work minimally. Nothing wrong with trying, but don't expect anything substantial. It's best to discuss tooth whitening with your own dentist who can go over all the options, as well as the pros, cons and expectations of each.

No: The act of brushing may cause your teeth to appear lighter if the brushing removed extrinsic stains. Lighting the tooth itself is usually accomplished with carbamide peroxide or hydrogen peroxide.

Probably not: Except for brushing off surface stain, baking powder should not whiten teeth.