Ferrofluid Spikes

Liquid grows sharp black spikes. Ask students to predict what will happen. Move magnet near sealed ferrofluid. Key idea: Magnetic nanoparticles align with field while surface tension resists deformation. Ask: How can a liquid make pointy shapes? Safety and cleanup: Use sealed commercial display; strong magnet teacher-handled. https://www.google.com/search?q=%22Ferrofluid+Spikes%22+science+demonstration+experiment