Alaska Science Camps, Fairs & Experiments

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Solution vs
Suspension

Many of Alaska's rivers contain large amounts of river silt. Of the Tanana it is said, "It's too thick to drink and too thin to plow." Many of our islands and riverbanks are made of silt that has been carried downstream for thousands and thousands of years.

When a substance is dissolved in a liquid, like sugar in coffee, the substance remains in the liquid. It is a solution.

When a substance is floating around in a liquid, held there by current or turbulence, it is a suspension. It will eventually settle if the water is still.

The Yukon is a mighty river, yet ocean boats cannot enter the mouth. Why? There has been too much silt deposited in the mouth. We often talk about the Yukon-Kuskokwim (Y-K) Delta. A delta is the land formed by the deposit of silt in a river mouth. The current has slowed as it bucks the tides, and the silt comes out of suspension and settles.

 EXPERIMENT: DISSOLVING

Heat water in a clear Pyrex container. Pour in measured amounts of sugar while stirring until it can hold no more sugar. It is now saturated with sugar. Pour the liquid off the top into another container.

As long as the water is kept at that temperature, all the sugar remains in solution.

Now cool the sugar water. What happens? What conclusions can you draw about the ability of water to hold dissolved sugar? Heat it again. Does the sugar again dissolve?

Can you taste the difference in the amount of sugar dissolved in the hot and cold water?

Pass the water containing dissolved sugar through a coffee filter. Is the sugar filtered out? By taste, compare some filtered sugar water with unfiltered sugar water.

You might try some of the above activities with salt. Is sugar the only substance that will dissolve in water?

 EXPERIMENT: SUSPENSION

 SEDIMENT SUSPENSION

Collect river water from a silty river. Let the water sit overnight. What happens to the silt? Stir it up again. Let it settle. What conclusions do you draw?

Heat the water in a clear container and keep it heated with an alcohol lamp or other heat source. Let the silt settle. Does the temperature of the water influence the amount of silt that can be held in suspension? Or is that influenced by the motion of the liquid?

Pass silty water through a coffee filter. How much of the silt passes through the filter? Let the filtered water settle for a while. Can you see the silt in the filter?

Boil silty water. Does the silt settle faster in boiled water than in cold water that hasn't been boiled?

If you are able, obtain silt samples from upstream, middle region and downstream of a large river. What are the differences? How can you explain this?

From the above experiments, what can you say is the difference between a solution (being dissolved in a liquid) and a suspension?

How are river deltas formed?

 Finding and Developing a Science Fair Project Examples of "Observe and Think" Projects 200+ Ideas for Science Fairs! Traditional Lighting Firestarting Traditional Firemaking Sharpening Fishing with Lures Rabbit Snares Spearing Fish and the Refraction of Light Chill of the Campfire Solution vs Suspension Seals & Beaver, Floating & Sinking Steaming Selecting a Birch Tree Spruce & Other Roots Spruce Gum Spear Throwing Berry Pickers Drum Frames Conclusion

A partner with the Alaska Rural Systemic Initiative

This material is based upon work supported by the National Science Foundation under Grant No. 0086194. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Contents

Camps as an Environment for Science & Culture

Culturally Relevant Science Fairs

Experiments

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