Salt Water vs Fresh Water

Activities to try

1. 1

   Build a reservoir graph, then zoom into the fresh-water slice

   Why it works: The water people can actually reach (surface rivers and lakes) is a sliver of a sliver: only ~3% of all water is fresh, and most of that is frozen in ice caps/glaciers or held underground, which is why usable fresh water is precious.

   1. Name each reservoir first (oceans, glaciers/ice caps, groundwater, rivers, lakes), then add its volume to a bar or pie chart one reservoir at a time; once all are added, notice that the ocean accounts for roughly 97% of the total (most of the pie, or a bar far taller than all the others combined).
   2. Zoom into the thin ~3% 'fresh water' wedge so it fills the view, then divide that fresh slice again into its parts (mostly frozen ice caps/glaciers plus groundwater, with a hair-thin sliver of rivers and lakes).
   3. Recompute or redraw the chart as reservoirs are included or excluded, so the proportions visibly change.
   4. Separately, retell the same data as 100 water drops sorting themselves into about 97 salty and 3 fresh, and note how few of the fresh drops are actually reachable surface water (fewer than 1 of the 100).
   5. State in your own words why accessible fresh water is limited, using the graph as your evidence.
2. 2

   Hands-on beaker and 100-drops demonstration

   Why it works: A physical pour-off is intended to make the 97/3 proportion and the even smaller accessible fraction tangible, reinforcing the graph evidence.

   1. Fill a 1 litre container to represent all of Earth's water, then measure out about 30 ml to stand for the fresh water, leaving the remaining ~970 ml as the salty ocean share.
   2. Set most of the fresh portion aside as 'frozen in ice caps' or 'underground', keeping only a few drops to represent the rivers and lakes we can easily use.
   3. Describe what each quantity represents and compare the reachable sliver with the whole container.
   4. Optionally re-tell the same split as 100 drops: about 97 salty, about 3 fresh, and fewer than 1 easily accessible.
3. 3

   Read and reason from a supplied chart

   Why it works: Learners can interpret proportions and comparisons from a given graph and connect them to the real distribution of Earth's water, surfacing both the salt/fresh proportion error and the belief that visible surface water holds most fresh water.

   1. Given a pie or bar chart of reservoir volumes, estimate what percentage of Earth's water is fresh.
   2. Order the reservoirs from largest to smallest by volume.
   3. Match each reservoir (oceans, ice caps/glaciers, groundwater, rivers, lakes) to whether the chart counts it as salt or fresh water, noting that some lakes and some groundwater are actually salty.
   4. From the chart, state where most fresh water is stored and explain the reasoning (teaching note: the largest single fresh store is frozen ice caps/glaciers, with groundwater the next-largest; very little is in surface rivers/lakes).
   5. Respond to the prompt: 'A friend says most of the water on Earth is fresh water we can drink. Is that right?' Explain the actual amounts and where most of Earth's water sits.