"Ounces" weird units, because in the imperial system (UK and many countries) and American system, they can refer to volumes or weights. If we're talking about a quantity of water, my assumption is that 10 ounces refers to 10 "fluid ounces" which is volume. To convert this to metric volume (milliliters), you multiply by 29.57, so that's about 300 ml.
I'm not sure how the mass of the water helps you, but since 1g of water = 1ml of water (isn't metric simple?), that's about 300 g of water.
Stephen La Rocque. >