Growing With Science Blog

This week our science fun has been inspired by a book that just came out, Planting the Wild Garden by Kathryn O. Galbraith and illustrated by Wendy Anderson Halperin. See Wrapped in Foil blog for a full review.

Planting the Wild Garden is a beautifully illustrated picture book that is a delightful introduction to the ways wild seeds move around (are dispersed).

Plants can’t move once they start growing, yet we see plants almost everywhere. How did they get there? Most travel as seeds. Seeds have many different ways to spread and scatter.

In this video from the Life of Plants by David Attenborough we get to see some marvelous footage of the amazing ways seeds move. Note: there is a pop-up ad.

Activity 1. Investigate seed structure and movement through observation.

Here at Growing with Science we have a regular feature called Seed of the Week. Take a look at some of the seeds and guess how they might be transported from place to place. For example, check the Chinese elm seeds (samara) with their tiny wings. Don’t they look like they could fly?

Go outside and look for seeds, particularly in the fall. Observe them and try to figure out how their structure helps them get from place to place. Look at them through a hand lens. Toss them in the air. Blow on them. Put the seeds in a puddle. See if they will stick to your sleeve. Think about where you see seeds and how they got there.

Activity 2. Floaters

As you saw in the video, seeds like the sea bean can float from place to place. They don’t have to be in a big body of water like the ocean either. A small trickle created by a downpour of rain may be enough to float seeds away.

Gather:

• Large bowl, sink, tub or aquarium to fill with water
• Seeds or fruits to test for ability to float:   coconuts, cranberries, a pinto bean or other dried bean, etc.

Predict what will happen to each item and then test each item. Let the seeds or fruit float as long as possible to show that they might reach land without sinking. You might want to cut open a cranberry to show the seeds inside.  (Remember that cranberries are harvested by floating them in ponds). Does a cut cranberry float?

More advanced activity:

Scientists in Hawaii needed to know how plants arrived on the islands in order to protect native species and prevent introductions of invasive species. A scientist named Henry Guppy placed different seeds in jars of seawater for several months to see how long they could float. Design your own experiment to test which seeds float in your area and investigate how they do it.

Have you ever gone to the beach or the shore of a lake? Look for seeds on the shore that were carried there by water.

Activity 3. Flying Seeds

Most of us have seen seeds flying in the air at one time or another. Dandelions, milkweeds, maple keys and cottonwoods are just a few examples of trees with seeds that ride the wind.

This slide show shows how humans can help cattail seeds disperse.

Dandelion and cattail seeds fly with structures that are like tiny parachutes. If you are interested, try investigating parachutes.

Advanced:
Design an experiment to test how far a dandelion seed can fly. How would you measure it?

Maple keys are so interesting that scientists take high speed movies of them to discover the secrets of their movements. According to this study, the keys produce swirling air like mini-tornadoes while they spin. Here the seed has been dropped in oil to make the whirls easier to see.

Do you see the tiny swirls that form over the end of the “tail” part of the key? Cool!

For more about maple key science, try these links:

Whirling Wonders

NASA Maple Seed Aeronautics

Maple seed science -some of links are broken, but go to Exploring Science and Design with a Maple Seed and click on the words under the pictures to find instructions on how to make the origami and other models to test.

Animals also transport a lot of different kinds of seeds. Whenever an animal, such as a bird, eats a juicy bit of fruit like this pyracantha berry, it ingests the seeds. The seeds end up on the ground later on. Other animals, like squirrels, may bury seeds and forget where they are.

Some seeds, like burdocks, hitch a ride by being sticky or latching on the fur of mammals.

We often think of big animals moving seeds, but tiny ones move a lot of seeds, too. Check for a related post at Wild About Ants for information about ants and seed dispersal.

Finally, by far the coolest are the seeds that pop out of the pods and shoot away. Plants with this kind of dispersal include jewelweed, lupines and Scotch broom. See if you can find a plant that does this and try it out.

And don’t forget to pick up a book about seed dispersal, such as Planting the Wild Garden, to learn more and inspire your own investigations.

Reading level: Ages 4-8
Hardcover: 32 pages
Publisher: Peachtree Publishers (April 1, 2011)
ISBN-10: 1561455636
ISBN-13: 978-1561455638

Book was provided for review purposes.

This weekend let’s try some experiments with water.

1. pH of the Planet

If you are thinking big, why not participate in the International Year of Chemistry’s  Water–A Chemical Solution: A Global Experiment? The organizers are inviting students from around the world to check the pH of local water sources and then report them. Take a look at the website for details. If you want to check out the experiment, look at the .pdf file in the right sidebar labeled Worksheet- PH of Planet, which gives details about the methods.

2. Water Temperature and Density

Gather

• 3 plastic cups
• 4 zipper top plastic bags
• sharpie pen to label the bags
• large container to hold water, or sink or bathtub
• warm water – about bathtub temperature
• cold water
• ice cubes
• Digital water thermometer (optional)

A. Density and Floating – Do bags filled with warm water versus cold water float the same?

Fill your large container with room temperature water. Place a few ice cubes and some cold water in a zipper top plastic bag. Close the top and let the ice cubes mostly melt, so you have very cold water. Label the bag cold. Fill another zipper top plastic bag with warm water and label it warm. Now place the two bags in the large container. What happens? Do both bags float? Does one bag sink? Why or why not?

B. Playing with Temperature – Does pouring water change its temperature?

Label the plastic cups 1, 2 and 3. Pour some of warm water into the plastic cup labeled 1 (say about 1/2 cup or so) and the same amount into cup 2. Take the temperature of the water in both cups, if you have a digital thermometer. The temperature should be the same in both cups. If it is not, dump the cups and refill with warm water again. Once they are the same, place cup 2 aside to serve as the control.

Now quickly pour the water from cup 1 into cup 3. Pour it back and forth from on cup to the other for about two minutes. End up with all the water back in cup 1.  Now take the temperature of the water in cup 1 and cup 2 again. Are the two temperatures still the same? Why or why not?

C. Does air change density with temperature?

If you still have warm water and cold water in separate containers, try this activity with air. Fill the remaining two zipper lock plastic bags with roughly the same amount of air, but it shouldn’t be completely filled. You can blow in the air and then quickly seal it up. Now place one bag in warm water (at least bathtub temperature) and the other in cold water. What happens?

(If you got the right amount of air in, the bag in the warm water should expand noticeably).

If you do these experiments, let me know what you find out. And it have a digital water thermometer, think up some more activities with water. I’d love to hear what you come up with.

Digital thermometers for aquariums are relatively inexpensive.

As the temperatures heat up, its time to pull out the ice and do some “cool” science.

1. Ice Spikes

Have you ever seen bumps or spikes come up from the ice cubes in your ice cube tray? SnowCrystals.com has a great discussion of ice spikes, how they form and how to grow some of your own. For more pictures and a movie, try Spikes on Ice Cubes.

2. Ice cube rescues

Give your child(ren) a challenge to “rescue” ice cubes floating in a glass of water with only a piece of string and some salt. Then watch this video to see how it is done.

3. Freezing and thawing water

Freeze water in various-sized containers and then set the ice “sculptures” out to thaw. (Set them in in deep bowl indoors or outside on a sidewalk or patio where a little melt water won’t matter.) Time how long it takes various sizes and shapes to melt with a watch or clock. Does size or shape influence melting time? How?

Try freezing a water-filled water balloon (set in a bowl first). Once it is frozen, what happens when you toss it? What happens when you freeze a balloon filled with air in a bowl of water?

4. Floating and sinking

Create an ice cube boat and float it to emphasize that ice is less dense than water.

Gather:

• ice cube tray
• cold water
• pie plate or shallow bowl
• plastic wrap
• toothpicks
• triangle of paper
• clay (optional)

Fill the ice cube tray with water. Cover the tray with a tight layer of plastic wrap, which will hold up the toothpicks. Stick a toothpick in the center of each cube, enough so that there is a least one for each child. When the ice cubes are frozen, remove from the tray. Insert a small triangle of colored paper on each toothpick to make a sail, and float the ice cubes in a bowl of cold water (the colder the better). Do the boats float? Do they stay upright? If not, try adding some clay to the bottom until the ice cubes are balanced. (This may be difficult at first, if the oily clay doesn’t stick to the wet ice. I found it did work with patience.)

5. Moving on to dry ice

Dry ice (frozen carbon dioxide) is available at many grocery stores. Just remember that it is much colder than regular ice and will require special handling. Always use gloves, and tongs are a good idea too. Never put dry ice in a swimming pool!

See this Steve Spangler video for some ideas and handling suggestions.

Ice is so much fun to experiment with in the summer. Let me know if you have any other experiments to do with ice or activity tips.

For more information, try these books:

and these related subjects:

Ice Scientist: Careers in the Frozen Antarctic (Wild Science Careers) by Sara L. Latta

Pioneering Frozen Worlds by Sandra Markle