Chemistry (Celby Ruiz)
Title: Lava Lamp: By using two types of state of Matter: liquid and gas we are able to produce not only something interesting but a great reaction and mixture at the same time.
Principle(s) Investigated:
Understanding:
1. density of liquids.
2. polar/non polar compounds.
3. Buoyance
4. States of matter
5. Potential energy
HS-PS3-5.
Develop and use a model of two objects interacting through electric or magnetic fields to illustrate the forces between objects and the changes in energy of the objects due to the interaction. [Clarification Statement: Examples of models could include drawings, diagrams, and texts, such as drawings of what happens when two charges of opposite polarity are near each other.] [Assessment Boundary: Assessment is limited to systems containing two objects.]
Materials:
1. A plastic bottle (does not need a lid)
2. water
3. oil
4.alka seltzer (a few packets)
5. Food coloring
Procedure:
1. Obtain all the materials. fill an empty bottle with water ~ 1/3 of the the bottle
2. Now pour the oil to fill up container almost to the top (leave a small space for air)
3 add a few drops of food coloring (10 or so depending of size of bottle)
4. let them settle in do not shake bottle to mix (the water should be the only thing soaking in the food coloring)
5. Once your able to see the full separation of water and add half a tablet of alkazelter. start with one then two then if you can 6 and etc...
7. Observe your findings. What happens?, why?
Student prior knowledge: basic principle of density /displacements of water / difference between reaction and mixture.
Explanation: A polar molecule is made up of a negative and positive charge. While non polar molecules have an equal charge. In this case when dealing with water, a polar compound it is made up of two positively charged H+ and one -O (negative) these all interact and attract to each other. Just like a magnet all molecules bind together, pushing away the other molecules (oil). Oil in nonpolar is has no charge, which is what makes the two liquids separate and form the layers. Now why the oil floats to the top is a different explanation, This has to with density. Oil is less dense than water so although there is more oil than water in the bottle due to the low density of oil it floats to the top.
During this experiment we will witness the separation of two liquids and when it is disturbed with alka seltzer. The potential energy is activated. As the tablet sinks to the bottom it will grab some of the water molecules and bring them to the top mixing it with oil but as the carbon dioxide is released the water the merges back to the bottom, and reunites with the water molecules.
Potential energy = stored energy (in this case the tablet and water)
Citric acid and sodium bicarbonate both individually dissolve and create the carbon dioxide
HC6H7O7 + NaHCO3 —> NaC6H7O7 + H2O + CO2 (g)
Questions & Answers:
1. Why doesn't the oil attract the food coloring? - there is a difference between mixture and reaction. A reaction changes the chemical structures while a mixture just a combination or addition without a reaction or new product taking place. So an example of a mixture is food coloring with water at the same density . Compared to the water and alka seltzer is a reaction because carbon dioxide is produced.
2. What does the alka seltzer affect? The alka seltzer is what provides the energy needed in order for the two can liquids. As the potential energy from the bottle and alka seltzer reacts it sinks and reaches the bottom it dissolves and gas in generated in this case carbon dioxide as it is released it gets a hold of a water molecule and rises in the bottle so it can finally be released at the top. it now floats to the top because it is less dense than both oil and water.
3. What if we top off the bottle? nothing happens if the cap is put on the bottle but if the bottle is capped and the reaction between the water and alka seltzer is still active the pressure build up from might cause the bottle to inflate or even explode. You can test it, as the reaction is happening put your hand over the bottle for a sec or two and you'll see that pressure build up as you remove it just like opening a fresh soda can. This will now be an experiment on pressure.
Applications to Everyday Life:
students can better understand the principles of inter molecular polarity. and can also relate it to other things in every day life such as such this specific example a lava lamps or salad dressing; cooking in general.
Also future building block to learning about
1.oxidation such as rust. ex: why we grease a bicycle chain.
2. emulsifiers : ways we mix the two compounds (mayonnaise)
3. Homogenization
4. kinetic energy
Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.
Videos: youtube video
http://beam.ucla.edu/sites/default/files/docs/Lava_Lamps.pdf