1. Bimetallic Strip
The bimetallic strip is composed of 2 metals that are arranged as a sandwich.
One of those metals has a lower melting point (turns to liquid) so the molecules of that metal get excited
easier. When the molecules get excited they move faster and take up more room. As the molecules of one of
the metals began to need more space, the other metal stayed the same as it was. So one side grew and the
other side did not.
http://www.veeco.com/learning/learning_melting_elements.asp
melting points
2. Ball and Ring
In the second step when you heated the ball (and not the ring), the ball should have expanded because the
molecules need more space to live when heated. So the volume (size) of the ball increased and could no
longer fit through the ring.
For the math experts: What happens to the balls density when the volume is increased?
D = M/V
3. Convection Currents in Water
As in the above experiments, when matter is heated, the molecules are excited and need more space to live.
The volume that the substance takes up is greater, the mass of the substance doesn’t change and so its’
density lessens.
Think of the container as almost having two layers of different densities. The layer of water on the bottom
has a lower density since it is closer to the heat. The layer on top has a greater density since it begins to cool
near the surface.
The more dense cool water wants to sink, pushing the less dense warmer water to the top.
4. Convection Currents in Air
The air just above the candle is the warmest and less dense than the air around it. The cooler and more dense
air sinks to the bottom pushing the warmer air up and out the chimney.
5. Can Crusher
When water vapor, a gas, is cooled, it condenses into a liquid.
The molecules in a gas are moving much faster as a gas and take up more space. Molecules in a liquid are
moving slower and taking up less space.
Just before you dunked the can in ice water, the can was full of water vapor. The molecules of the gas were
pushing out with equal force to the air pressure pushing in.
When it condensed to liquid, the liquid takes up less space so there was more room inside the can. If you
cooled the can with the top up, air would have rushed in. However you cooled the can with the top
underwater that blocked the sir from rushing in.
Now the force from the molecules pushing out is much lower than the force of air pressure pushing in.
Name __________________________________ Period ______ Date ________________
Directions: Fill in the missing words in the paragraphs below.
In a lava lamp, the life of a lava “blob” is pretty simple. The blob heats up and
1__expands__________________, it is pushed up by 2 __buoyant__________ force, it
cools and 3 ___contracts______________ and falls back down due to
4___gravity_____________. The lava lamp works because of changes in the
5____density_______________ of the blob during its life. As the
6 _____density________________ of the "lava" changes, the buoyant force changes.
The 7 ____buoyant___________ force, is the force that allows the blob to overcome the
force of gravity.
DIRECTIONS: The boxes below represent the density of the lava and the density of the liquid in each
lamp. In the circles, write in 1, 2 or 3 depending on where these conditions would be found in the
lava lamp.
DIRECTIONS: Under each box above, draw an arrow that represents the buoyant force. Be careful,
some will not have a buoyant force.
Directions Part 1: Draw in the molecules representing the air surrounding the balloon and the
molecules of the air in the balloon. Remember a HAB rises and falls for the same reason a lava blob
rises and falls. (Density Density!)
Directions Part 2: Fill in the missing words in the paragraphs below.
The life of a hot air balloon is pretty simple. As the HAB heats up and
1 ___expands_____________, the hot air molecules move 2 ___faster________ and
some 3 ___escape____________ through the bottom. This lowers the
4 __mass__________ so it lowers the 5 ___density____________. With a lower density
than the air surrounding air, it is pushed up by 6 __buoyant____________ force. As it
cools and 7 _contracts_______________, the molecules that escaped now return, the 8
__mass______________ increases and the density
9 __increases_______________. The HAB now has no buoyant force and
10 ___gravity________________ pulls it back to Earth.
In an HAB (as in a lava lamp), as the 11 ___density______________ changes, the
buoyant force also changes.
Name ________________________________________ Period _______ Date _____________
Who am I?
1. I move faster when heated. What am I? ___MOLECULES_______________________
2. I cycle over and over because my top is heavier than my bottom. What am I?
_____CONVECTION CURRENT- WATER________________________________
3. One of my sides “grew” faster than the other. What am I? _____Bimetallic
Strip_____________________
4. Every time I try to get the group heated up, my top cools down. What am I? __convection current water________________________
5. My whole body got bigger when I was placed in the flame. What am I? __ball (in ball and
ring)________________________
6. Even though my mass didn’t change, my volume increased. What am I?
_ball_________________________ What other physical characteristic went down?
____density______________________
7. Just because all my neighbors moved farther away, our population hasn’t changed. What am I?
__mass_________________________
8. My friends say they need more space. I wonder why they need more space? _____heat
applied_________________________
9. When I grew larger my __volume______________ increased?
10. My clothes didn’t fit after I was heated. What am I? ___ball (and ring)_______________________
11. The neighbors just above me have changed and are being pushed out of town. Where am I located?
_____convection box- right above the candle_______________________________
12. Because our entire population has moved farther away, our city has grown larger. What
characteristic has increased? ___volume____________________________
13. One metal became “excited” to heat more than the other. What am I? __bimetallic
strip________________________
14. My molecules were much closer together on my top layer than my bottom layer. This caused my top
layer to tumble down. What am I? ___convection current - water_______________________
15. I am composed of composed of 2 metals that are arranged as a sandwich. What am I? ___bimetallic
strip_______________________
16. When I move faster, I spread away from my neighbors. What am I?
__molecules________________________
17. I am just along for the ride. What am I? __paper punches or smoke________________________
18. Everything was great until we started to ___heat up/boil_______________________. Now we are
so different, we just seem like we are moving in circles! What am I? _convection currentwater_________________________
19. The space we occupy has grown but the number of molecules has stayed the same. My
volume___________________ has increased, my _mass______________ has stayed the same but
my __density___________________ has decreased.