Monday, April 30, 2012

Mixtures: The Mistake

 Originally posted on March 11, 2010

This is a fun, open-ended lab for your students to put into practice that which they've learned about separating mixtures. Read the following story to your students (this is the original, you'll want to swap out "Home Ec" for whatever's appropriate in your school). Then, provide them with a sample of the salt and pepper mixture, a variety of tools, and let them have at it.

You may want to read the story to them the day before they'll perform the separation... gives them time to come up with a plan and gives you the opportunity to gather any materials they may wish to use that you hadn't thought to put out.

The Mistake
What kind of day was it? A day like all days - only THE SUBSTITUTE was there. The place was Home Economics and the substitute - one Mrs. Dimwitty. In her demonstration, Mrs. Dimwitty was to add salt and pepper to her baked dish. In trying to save time, Mrs. Dimwitty mixed the salt and pepper together before class. Upon reading teh recipe very closely, she discovered that the salt and pepper had to be added at different times. What an embarassment. What would she do now? All teh salt and pepper she had was in one jar - all mixed up. One of Mrs. Dimwitty's students said she could help if allowed to go to the science department. A short time later she came back with two jars - one containing salt, the other containing pepper. What a relief. The casserole would be a success.

In this lab you are to separate the salt and pepper mixture that you find in your test tube into two piles. Salt must be piled on one paper towel - pepper on another. You WILL NOT get another test tube so be careful. Don't throw anything down the drain until the end of the period. After you have separated the salt and pepper, bring them to the front desk for inspection. There should be no salt in the pepper and no pepper in the salt. After your separation has been approved, give a step by step description of what you did on the back of this sheet.

Friday, April 20, 2012

Diffusion: Perfume in the Room

 Originally posted on March 10, 2010

Place an open container of perfume (or other scented substance, such as vanilla) in a corner of the room. Have students raise their hand when they first smell the scent. Or, they could quietly note the time at which they first notice it and you can analyze the data later. You should find that students nearest the container are the first time notice it and it spreads outward from there.

To keep the results as honest as possible, don’t tell students where you’ve placed the container or what scent you’ve used.

Wednesday, April 18, 2012

Rocks: Sugar Cube Rock Cycle

Originally posted on March 9, 2010

Have your students complete the rock cycle, using sugar cubes.

You'll need:
--Sugar cubes,
--Squares of aluminum foil, folded into a "boat"
--Hammer (or other smashing device)
--Candles (birthday or Hanukkah)
--Lumps of clay
--Test tube holder

Each student begins with a sugar cube, which reprsents the original sedimentary rock. Then...
--Weathering: Crush the rock with a hammer (or heavy book)
--Erosion: Move the crushed rock into the foil boat
--Heat/Melting: Using the test tube clamp, hold the foil boat over the candle flame until it melts. (Use a lump of clay as a candle holder).
--Cooling: Set the melted sugar aside for several minutes.
--Weathering: Break the new, igneous rock into pieces.

Warning: Melting sugar smells! Forewarn your neighbors and administrators before your classes get to work, so as to avoid unnecessary calls to the fire department!

Monday, April 16, 2012

Water: Drops on a Penny

 Originally posted on March 8, 2010

How many drops of water do you think a penny can hold? Make a hypothesis as test it out... you might be surprised.

When beginning a unit or lesson on water, I like to ask my students to give me as many words as they can think of to describe water. I make a list on the board and at the end, add one or my own: sticky. Students look at me like I've lost my mind, but once they start on this experiment, they start to understand my description - the water drops stick to one another. A great introduction to the properties of adhesion, cohesion, and surface tension.

Encourage students to make up their own experiments. For example, which side holds more, heads or tails?

After going through the activity once, you can mess with your students a bit - put a little liquid soap in their water supply, or rub a little soap on the penny. The soap interferes with the surface tension and the pennies can't hold nearly as much water.

Friday, April 13, 2012

Favorite Website: Middle School Science

Originally posted on March 5, 2010

Get your printers loaded and ready to go... Middle School Science is another great website loaded with labs, lessons, and activities all ready for you to print out and take into your classroom. To find the goodies, click on the appropriate branch of science at the top of the home page (maybe it's just me, but every time I stop by the site, I start looking for them in the list in the left-hand margin and can't find them. Good reason... they're not there! They're at the top. If my head wasn't screwed on tight...).

Bonus... this year, she started a blog to go with her website. I haven't yet worked my way through the archives, but I will in the very near future. And will be subscribing to the feed as well.

Wednesday, April 11, 2012

Atoms: Rutherford's Gold Foil Experiment

Originally posted on March 4, 2010

This is an original demonstration I created to try to help my students understand Rutherford's experiment: what he expected to have happen, what actually happened, and why it was significant. The demonstration is a bit crude (and it's starting to fall apart) - there's certainly room for improvement, but I think it does help students visualize what was happening. Please let me know if you find a way to improve upon this demonstration - I would love to hear about it.

Prior to Rutherford's experiment, the going theory about the atom was Thomson's Plum Pudding model. In this model of the atom, negatively charged material is scattered throughout the atom.

In Rutherford's Gold Foil experiment, he set out to shoot a beam of atoms at a thin sheet of gold foil. Based on the Plum Pudding model, one would expect most of the atoms to bounce back because the "negative" material is scattered throughout the atom, not allowing much room for atoms to pass by.

Instead, most of the atoms went straight through the gold. The resulting conclusion was that gold atoms must be made mostly of empty space, with a large central nucleus.

To create my stunning visual aids, I collected:
*a couple dozen small (~1") styrofoam balls
*a styrofoam disk (~2" in diameter)
*2 empty cereal boxes (on the larger size)
*a very large needle (used for upholstery)

Box 1: Thomson's Plum Pudding Model
-Cut open the sides of your cereal box, I left them on as flaps, to protect the model.
-Use the needle to sting the styrofoam balls onto the thread. (I used about 4 balls per thread and about 6 threads - adjust to the size of your box accordingly)
-Tape the ends of the threads to the top and bottom of the box.

Box 2: Rutherford's Model
-Cut open the sides of your cereal box, I left them on as flaps, to protect the model.
-Use the needle to run the thread through the styrofoam disk. Instead of trying to poke the whole way through the diameter of the disk, I ran thread through two holes that were poked through the flat part of the disk (examine the above picture).
-Tape the ends of the threads to the top and bottom of the box.

To demonstrate:
Rutherford thought he was shooting atoms at something resembling Thomson's model. Use an extra styrofoam ball and toss it at Box 1. The majority of the time, the ball should bounce back, because there isn't room for it to fit through. This is what Rutherford expected to have happen.

But... that's not what happened. Instead most of the time the atom (ball) passed through. Pull up Box 2 and toss the ball at it. This time, the ball should pass through a lot of the time. The only time it will bounce back is if it hits the nucleus.

Monday, April 9, 2012

Microscopes: Water Drop Microscope

Originally posted on March 3, 2010

Cut a 1” square out of the center of an index card (the shape and size are not important, you can decide how accurate you want students to be). Place a small piece of plastic wrap over the cut-out area and tape it so it’s taut. Place a drop of water on the plastic – you want it to maintain it’s drop shape, not spread out. Look through the water drop at some small writing, newspaper pictures, etc. The curve of the water drop will magnify what you are looking at, creating a very simple microscope.

I like to have students complete this activity after they complete their microscope quiz. I give out extra credit for anyone who takes their microscope home, shows their parents and has their parents write a note letting me know what they shared.

Friday, April 6, 2012

Minerals: Cost of 2L of Gold

Originally posted on March 2, 2010

Thanks to the soda/pop industry, 2 liters is a volume students are readily able to visualize. And, 2 liter soda bottles are readily available to use as a prop.

Ask students to imagine the soda bottle filled with gold (or silver or platinum). Use the internet (or newspaper) to find the current price for gold (gold is traded, thus the price fluctuates – get up to date information) as well as the density of gold. Then do the math (work through it with your students):

2L x 1000mL/L = 2000mL

2000 mL x 19.3 g/mL (density) = 38,600g

38,6000g x 0.035 (conversion unit) ounces/g = 1351 ounces

1351 ounces x $1,695.30 (price)/ounce = $2,290,350.30

Don't you wish you had a 2L bottle filled with gold!!!

Wednesday, April 4, 2012

Air Pressure: Crush a Soda Can

Originally posted on March 1, 2010

Place a small amount of water in an empty soda can. Place the can on a hot plate and heat until the water boils. While waiting, prepare a large container of cool water. Once the water has begun to boil, use tongs to pick up the can and quickly turn it upside down and place it in the water bath. The air in the can heats up, the air molecules start moving faster and some find their way out of the can, creating an area of low pressure. Turning the can upside down into the water creates a seal in which no air molecules are able to re-enter the can. The pressure outside of the can is greater, and the can is crushed.

To see a “real life” example of this phenomena, check out what happened to this train car when it was washed with hot water and sealed before it was cool.

Monday, April 2, 2012

National Science Teachers Association

 Originally posted on February 26, 2010

If you're teaching science, consider membership in the National Science Teachers Association. Along with membership comes a subscription to a great journal. Membership is a bit pricey if you're paying out of pocket... Even if membership isn't in the works for you, check out the website for some interesting articles and check out the store - lots of great book titles there. You can always check and see if your local library can get you any of the titles you're interested in.