PART 1: THICKNESS OF AN ALUMINUM FOIL

An aluminum foil is really thin. Here is a way to find the thickness of a foil.
The density of aluminum is about d = 2.7 g/cm³. That means if you cut out a cube 1cm x cm x 1cm  of chunk aluminum, its mass is ________.

1) Cut a piece of piece of an aluminum foil 10cm by 10 cm. !!!! It has to be exactly 10cm. So make sure the edge matches the zero and that you are not using the inches side of your ruler. Be neat. Start over if you mess up. You can trace your square with a pen before cutting it.
so width = W = _______ cm and length = L = ________ cm

2) Use a sensitive scale and scale your piece to the nearest 0.01g. The best way is to compact the aluminum. mass = m = ________ g
(keep as much decimals as possible)

3) Using the mass of your sample m, its width W , its length L and, its density d  you can now find the thickness of the sample.
That is, you can now find the height of the foil. THink. I can't help you. don't ask me. try without hint.

hint:Think of the sample as being a box. You know the width, the length and you try to solve for the height H.
You know volume of a box = V = W x L x H. You also know d =  m/V. Substitute the numbers and solve for H. YOU CAN DO IT!

H = ________ cm. Convert to mm. H = _________mm.  (you should know how to convert cm to mm)
convert to micrometer. H = __________ micrometer. ( 1mm = 1,000 micrometers).

4) Why did you have to use this method to find out the thickness of an aluminum foil ? Why didn't you use a ruler ?

PART2: THE DENSITY OF AIR

Let's try to find the density of air. Take a balloon and weigh it on sensitive scale.
m1 = ________g. (to the nearest 0.01g).
Fill the balloon with air. (by inflating it !). Tie the end.
Place the balloon on the scale. now the mass is m2 = ________g.
This shows that air is matter since it has some mass. Find the mass of the air inside the balloon. m = m2 - m1 = __________g

Use a string to find the radius of the balloon: Give your balloon the shape of a sphere before. (circumference = 2 pi R ). Use your TI to find Pi.
circumference = __________ cm  so R = ________cm
Estimate the volume of the sphere V = ___________ cm³ (volume of a sphere = 4 pi R³ / 3)

Use the value of m and V to estimate the density of air. calculated d_air  = __________ g/cm³

The true value is true d_air = 1.3 10^-3 g /cm³. Are you close?
Let' s find the percentage error.
A) Find the difference between the calculate value and the true value _______ g/cm³
B) divide the number by the true value  _________ (no unit anymore).
C) multiply this number by 100 you get the percentage error. %error = _________ %.  Is it over 20% error ?
What do you think were sources of error ?

GOING FURTHER (at home - use internet / other teachers / books / friends )
Use another paper. Not enough space here. You can attach pictures but be very short. If you cut and paste from wikipedia or other sources, you will lose  points. Use your own word. This is not an English essay.

The method you used to find out the thickness of an aluminum foil is an indirect method of measurement. It is commonly used in Sciences.

A)For example, you can't see the interior of the EArth. However, you learned in Middle School that the Earth has an inner core, outer core, a lower mantle, upper mantle an a crust. Each layer is in a different state of matter/ How do we know that ? do you think we drilled up to the core ?
Search on the Internet to find out what is the tool used by Geophysicists to "see" inside the EArth.


B) We can watch a baby moving inside a womb. of course, we can't drill into a person to see the baby. Here again, an indirect method is used.
What do we use to "watch" the baby ?

C) you have a broken bone. To check on the fracture, the doctor would not dig into your flesh to measure the damage.
He has to use an indirect way of measurement. Explain and describe.

D) We know the composition of the Sun and of the other stars. We know that even before traveling in space.
How is it done? EXplain. Do some search on the Internet. Ask other teachers. not me.


F) During World War II the Nazis tried to invade England. But each time they sent a plane over there, trying to surprise the British ,  there were surprised
to always find British planes waiting for them and ready to fight. They thought British planes were too numerous and they gave up to invade England.
What the Germans didn't know is that the British were using a secret new technology called RADAR. Explain how it works and why it made a difference during WWII. Today, on the highways, the radar is used my policemen. Why ?  What RADAR stands for ?

G) A seismograph is a device used to record earthquakes. If the Earth shakes somewhere, seismic waves travel inside the earth or along the surface of the earth and you can record these waves with a seismograph, at a remote place, far from the source. If there is an EQ in California, seismographs placed on the East coast can record the quake and we can figure out its location and magnitude.
This technology was developed by the American Army during the cold war. THey were trying to spy on the communist countries because they could not  directly see what they were doing. What do you think they were trying to find out ? The Earth can shakes because of an EQ but not only. Other event can shake the ground. Like .......


H) If you want to measure the depth of an ocean you can't dive with a meter stick and measure the depth. You need to use an indirect method. What do we use  ? THis device was also developed by the army during WWII. Once the war over, the scientists could use it to study the bottom of the oceans and the oceanic ridges that separate tectonic plates.They found out that Wegener was right. right about what ?
Who was Alfred Wegener ?