Experiment with Water and Ice

We have put 1 liter of pure water and ice prepared from 1 liter of clean tap water into the device. We expected that 8 minutes is enough time to warm up and melt the ice, but we were wrong. For better visibility in the photos we used few grains of KMnO₄. During the first minute was the temperature on the two bottom sensors raising similar to clean tap water. As we have mentioned, eight minutes was not enough time to melt the ice. Maybe it would be different if we melted the ice and the water during the experiment, but the goal was to observe the experiment without measurable external influences. There is also a screenshot where you can see the entire course of experiment.