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Category: Fun Science Activity (Page 92 of 112)

Weekend Science Fun: Tree Leaf Age

April 27, 2009 / / 3 Comments

This week’s topic is, well, timely.

A few years ago my son asked how long tree leaves live. Having grown up in an area with four seasons, I always thought leaves lived from spring to autumn, when they fell off. Here in Arizona, however, we have trees that are green year around and I had no idea how long the leaves of a lemon tree, for example, might live. Then I began to wonder if trees and shrubs grow new leaves throughout the spring and summer, or whether they have short burst where all the leaves come out and that’s it.

If you’d like to find out how long the leaves live on your trees or shrubs, choose some freshly emerged leaves and mark them with acrylic marker. You can tell the young leaves because they are a lighter, brighter green color and are toward the tip of the branch.

If you don’t have a marker, you could also mark the leaves with tags or ties, anything that won’t wear or fall off or interfere with normal leaf development and photosynthesis. Record how many leaves you tag, when you tag them, and roughly where they are in the tree.

Check your leaves periodically. You might want to mark more leaves each time if you see new ones. This is a long-term project, so be patient.

We marked some of the new leaves on our lemon tree a few years ago. Our marked leaves remained on the tree through one entire year. The tree dropped a lot of leaves a couple of times, but our marked ones held on. Unfortunately, our marked leaves were lost before the experiment was finished when someone — who didn’t know about our experiment — trimmed the tree. We are going to try again this year.

Let us know what kind of tree or shrub you choose and how long the leaves last. Let me know if you think we should do a contest for the oldest leaf.

How long do you think the oldest leaf would be?

lemon tree

Weekend Science Fun: Car Movement Physics

April 19, 2009 / / 0 Comments

Anyone in your family interested in cars and physics? Even if you don’t realize it, working with the first thing can teach you a lot about the second. Today we’re going to look at Newton’s Three Laws of Dynamics using toy cars.

Gather

  • A few blocks or books
  • A few toy cars that roll
  • A small action figure or doll, or a smaller block or penny that can ride on the car
  • Piece of cardboard big enough to use as a ramp (older children can use wood)
  • Marbles
  • Plastic eggs

1.    Newton’s first law states that an object at rest stays at rest, and an object in motion stays in motion, unless acted on by an external force.

To test the object at rest part, place a small block or action figure/doll on a car (even a penny will work). Push the car, taking care not to push the object resting on it. Usually the block or doll will “stay put” by falling off, or at least falling back, while the car rolls away.

Now roll the car with the block or doll riding on it towards a barrier, such as a book or larger block. When the car hits the barrier, what happens to the rider? Does it fly forward? The rider is trying to remain in motion even after the car stops.

A child may wonder why, if an object does indeed remain in motion, does the car eventually stop rolling? Think of some other forces acting one the car that we might not see. How would you test this?

2.    Force equals mass times acceleration F=ma

Toy cars and ramps

Raise a piece of cardboard on books, blocks or a piece of furniture. Roll cars of different sizes and weights down the ramp, or add weights to cars of the same size (you can tape on pennies). Do bigger cars go farther and/or faster?

Now push the cars rather than simply letting them roll. See any difference?

Older children can actually calculate the force by weighing the cars and timing them.

3. For every action, there is an equal and opposite reaction.

Most children are more than willing to crash their toys cars into each other to test this theory.

You can save wear and tear on the vehicles by creating demolition derby vehicles out of the bottom of a plastic egg and a marble. You can decorate the egg with a sharpie marker. Place a marble under the egg and roll it away. See what happens if you add smaller, larger or more marbles under the egg. What happens when two plastic egg racers crash?

plastic egg marble car

Edit:

NASCAR Physics for the Older Set
The Science of Speed is a series of 13 videos at http://science360.gov/ that relate physics to what you see on a NASCAR race track. Just click on the circles under the “Science of Speed:” text to navigate through the videos. Topics include drafting, tire pressure, and friction and heat. Note: there are car crashes.

Thanks to Karen of Leaping From The Box for contributing the NASCAR link. If you are a NASCAR fan, try her racing blog.

For more info:

Teaching Physics with Toys: Activities for Grades K-9 by Beverley A. P. Taylor, James Poth, Dwight J. Portman

(Amazon Affiliate Link)

Weekend Science Fun: Plant Propagation

April 11, 2009 / / 6 Comments

Want to get more greenery without spending the other kind of green (money)? Let’s take a look at how plants make more plants in ways other than from seeds.

A number of plants can be grown from parts of donor plants by taking what are called cuttings. The cutting is simply a stem with some leaves attached that has been cut off the donor plant. The cutting is then placed in water or moist soil, and over time roots develop.  Once the roots develop, plants in water can be moved to soil and in no time your new plant will be growing and sending out new leaves.

Examples:

Philodendron, geranium and coleus – cuttings can be started in water.

pothos

pothos

Pothos Ivy – cuttings can be placed in water, then moved to soil after roots develop.

jade

Jade plant  – cutting start in water or soil.

cactus pad

Prickly pear – can be started by simply placing pads in the soil.

saguaro seedling

By the way, cacti can also start from seeds. This is a saguaro seedling.

spider plant

Spider plant  – take the offshoots or baby plants and place in soil.

aloe with pups

Aloe and agave- the main plants send off small plants from the roots, called pups. The pups can be separated and replanted. The pups of the above aloe are slightly reddish in color and are towards the lower right in the pot.

Potential science experiments/activities:

1.    Learn the plant parts for different species of plants. For example, is the pad of a cactus a leaf or stem? What is a node? What is a petiole?
2.    Can you start a plant from the cutting of just a leaf, or does the leaf need to be attached to a stem?
3.    Treat some cuttings with commercial root starting hormone and compare to cuttings from the same plant without hormone. How do they differ over time? Figure out how many plants grow from each treatment, what their value is, and how much the hormone cost. Is it cost effective?

Edit: We got some hormone rooting powder this weekend and were surprised to find out that it is quite hazardous. You might want to read the label before you buy it. Be sure to read and follow all the instructions.

4.    Do jade plant cuttings start better in water or moist soil? What about in moist sand or cactus mix?
5.    Under what conditions do spider plants send out offshoots? How old do they need to be to start making more spider plants? How big? Do they make more when they are healthy or when they are stressed? How would you test these questions?
6.    Do spider plants ever flower? What about pothos ivy, aloes or agaves? If they don’t flower, can they make seeds?

7. Do aloes/agaves make more pups when they are in small pots, large pots, or when they are planted in the ground? This would be a long term study.

Hope you enjoy growing new plants. Let us know how your experiments turn out, or if you have any more suggestions for experiments or activities.

Note:  Most of the plants noted above can contain irritants or toxins, so keep them out of reach of small children.

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