Hydrometer Investigation Straw
Sand
Sealing
Wax
Estuary
Fresh
Ocean
Water
Water
Water
Students made a hydrometer by sealing the end of a straw with wax and adding some
sand until the hydrometer barely floated in fresh water. The diagram shows what the
students observed when they used the hydrometer to test water from three different
sites. Each water sample had the same temperature. Which of these explanations best
nts these observations?
salt water is denser than fresh water
O estuaries are less salty than fresh water
O oceans support more microbes than fresh water
O ocean water can freeze at lower temperatures