a block of wood has a mass of 100g and measure 10cm by 1cm by 20cm. It was placed into container of water. What will happen to the block of wood

volume of the wood block is 10 x 1 x 20 = 200 cc

density of wood = mass/volume = 100 g/200 cc = 0.500 g/cc
The density of the wood is less than the density of water (1.00 g/cc) so it will float.