A solid block floats in fresh water. The block is then placed in seawater, which is denser than fresh water.
What happens to the block?
It floats higher, with less of its volume below the surface
It floats lower, with more of its volume below the surface
It sinks, because the upthrust from seawater is smaller
It floats at the same level, because its weight is unchanged
50 exam-style questions on OCR GCSE Physics 1.3 Pressure, covering 1.3.1 Molecular motion, temperature and gas pressure, 1.3.2 Gas pressure at constant volume, 1.3.3 Compressing and expanding gases, 1.3.4 Gas volume and pressure at constant temperature, 1.3.5 Doing work on a gas, 1.3.6 The Earth's atmosphere and atmospheric pressure, 1.3.7 Atmospheric pressure and height, 1.3.8 Floating and sinking, 1.3.9 Pressure in liquids and upthrust, and 1.3.10 Pressure differences with depth. Each one has a worked solution and a mark scheme showing where the marks go.