Candle Beaker Demonstration (Stephen)
Author
Stephen
Principle(s) Illustrated
The main purpose of this activity it for students to develop and revise a model. It is also and excellent activity to make claims and argue based off of evidence. Numerous physical principles can be addressed (conservation of matter, energy, work, center of mass, volume, pressure, temperature, etc.)
Standards
SEPs
1. Asking questions (for science) and defining problems (for engineering)
2. Developing and using models
3. Planning and carrying out investigations
4. Analyzing and interpreting data
5. Using mathematics and computational thinking
6. Constructing explanations (for science) and designing solutions (for engineering)
7. Engaging in argument from evidence
8. Obtaining, evaluating, and communicating information
CCCs
2. Cause and effect: Mechanism and explanation. Events have causes, sometimes simple, sometimes multifaceted. A major activity of science is investigating and explaining causal relationships and the mechanisms by which they are mediated. Such mechanisms can then be tested across given contexts and used to predict and explain events in new contexts.
4. Systems and system models. Defining the system under study—specifying its boundaries and making explicit a model of that system—provides tools for understanding and testing ideas that are applicable throughout science and engineering.
5. Energy and matter: Flows, cycles, and conservation. Tracking fluxes of energy and matter into, out of, and within systems helps one understand the systems’ possibilities and limitations.
7. Stability and change. For natural and built systems alike, conditions of stability and determinants of rates of change or evolution of a system are critical elements of study.
NGSS Disciplinary core idea standards
PS1.B: Chemical Reactions
Chemical processes, their rates, and whether or not energy is stored or released can be understood in terms of the collisions of molecules and the rearrangements of atoms into new molecules, with consequent changes in the sum of all bond energies in the set of molecules that are matched by changes in kinetic energy.
Questioning Script
Prior knowledge & experience:
Students are familiar with chemical reactions, combustion, atmospheric pressure, the ideal gas law, Dalton's law of partial pressure, work, pressure, kinetic molecular theory, phase changes gravitational potential energy, and temperature.
Root question:
What will happen when the graduated cylinder is placed over the candle?
Target response:
The number of moles of gas in the cylinder decreases as water vapor condenses. This reduces the pressure in the cylinder. The atmosphere does work and applies a force over a distance to increase the height of the center of mass of the water.
Common Misconceptions:
The mass from the candle disappears
Oxygen is burned. It disappears when it burns.
The thermal expansion from the heat added by the candle is the primary cause of this phenomenon.