The following lesson plan has been modified to follow the format of a flipped classroom. This will allow students with different needs to take longer or pause the videos where they think they did not get it. During the lab, only experimentation will take place and students will have some knowledge of what it is expected not only about content, but also about lab procedure. Students will be able to try different pressures and temperatures with the simulator. Finally, we will flatten our classroom by sharing our results with the rest of the world in The International Boiling Point Project, from where we will later have a discussion.
WATER’S BOILING
POINT LAB
Summary:
This
lesson allows students to investigate water’s boiling point (physical property)
through experimentation. This lesson is modified to help students with special
needs have access to other resources to understand the boiling point better. It
could also have connections with students around the world through The
International Boiling Point Project, a worldwide project where students across
the globe measure the boiling point of water at their location and submit the
data to The International Boiling Point Project website, where everyone
participating in the project has access to the data.This will allow students to
understand that the boiling point is modified according to the altitude.
Grade:
Science - 8th Grade
Materials:
● thermometer in °C (one per group)
● 250 ml beaker (one per group)
● 500 ml graduated cylinder (one per group)
● Bunsen burner or hot plate (one per
group)
● ring stand and bracket to hold
thermometer (one per group)
● crushed ice (enough to fill one beaker
per group)
● data notebooks
● Syringe
● Clay
Background For
Teachers:
What is the boiling point?
The boiling point of pure water is highly dependent on
atmospheric pressure. At sea level distilled water boils at 100 °C; as
elevation increases, and atmospheric pressure decreases, the boiling point of
water decreases. In this lesson students will measure boiling point of water
for the elevation of ASF[2]. Students are engaged in the scientific
process, and need to follow specific experimental procedures in order to
collect accurate data, and observe the phase change of water from a liquid to a
gas. If possible, students can post data for the school on the international
website that allows comparison of water boiling point temperatures from around
the world.[3]
Web Sites
Student Prior
Knowledge:
● Ability to measure water temperature with
a thermometer.
● Ability to measure a specific water
volume with a graduated cylinder.
● Ability to use a hot plate or Bunsen
burner to boil a beaker of water.
● Understanding that boiling is the process
where a liquid is converted to a gas by increasing the energy, making the
molecules move faster.
Intended Learning
Outcomes:
1. Use Science Process and Thinking Skills
a. Observe objects and events for patterns and record both
qualitative and quantitative information.
d. Select the appropriate instrument; measure, calculate,
and record in metric units, length, volume, temperature and mass, to the
accuracy of instruments used.
e. When given a problem, plan and conduct experiments.
3. Demonstrate Understanding of Science Concepts and
Principles
a. Know and explain science information specified for
their grade level.
d. Solve problems appropriate to grade level by applying
scientific principles and procedures.
Instructional
Procedures:
Students should work in small groups (two to four students
per group). Before performing the experiment, students should have seen the boiling point video[4], 'Experiments' - Evaporation, boiling and Bubbles[5] and Science Help boiling point[6] to have a flipped classroom. Students will learn potential variables
influencing the boiling point of water: pressure, elevation, amount of water,
initial water temperature, room temperature, heating device. During class
teacher should start by asking students to write a hypothesis for the variable
that has the greatest impact on water boiling point.
Give students the following procedure on a worksheet or
lab journal for this experiment:
Experiment
Day 1: Thermometer Calibration
1. Determine elevation of the school. A GPS
or local topographic map can be used to find elevation, or a specific zip code
can be entered into the National Weather Service Forecast webpage in order to
determine elevation Forecast Error(http://forecast.weather.gov/MapClick.php)[7];
other websites are also available).
2. Thoroughly clean beaker with dish soap,
rinse well with distilled water.
3. Fill beaker with crushed ice and
distilled water. Smaller pieces of ice work better than larger pieces; The goal
is to make slush, similar to the consistency of a snow cone.
4. Insert thermometer in the slush and
record the temperature. The slush temperature can be assumed to be 0 °C.
5. Derive a correction factor based on the
slush temperature measurement and record data. For example, if the thermometer
read 0.2 °C in the slush, the correction factor is -0.2 °C, meaning 0.2 °C
should be subtracted from all subsequent water temperature measurements; and if
the thermometer read -0.2 °C in the slush, the correction factor is 0.2 °C,
meaning 0.2 °C should be added to all subsequent water temperature
measurements.
6. Remove thermometer from slush and empty
slush from beaker.
Day 2: Water Boiling Point Measurement –
Practice Run
1. Select a volume of water to boil and
record data; volume must be between 250 and 750 ml in order to post data to The
International Boiling Point Project website and each group should use the same
water volume each time the experiment is conducted.
2. Evaluate current weather conditions
(clear, partly cloudy, overcast) and record data.
3. Use graduated cylinder to measure
selected volume of distilled water and pour it into beaker.
4. Place beaker on hot plate or over Bunsen
burner.
5. Measure laboratory air temperature with
thermometer and record data.
6. Insert thermometer into the bracket
connected to the ring stand; submerge thermometer in water. Thermometer should
be suspended in the water at least 1 cm above the bottom of the beaker; it
should not touch the bottom or sides of the beaker.
7. Measure initial water temperature with
thermometer and record data.
8. Turn on hot plate or Bunsen burner to
begin heating water. If hot plates or burners have adjustable heat settings,
400-500 °C is a reasonable temperature.
9. Record temperature every minute; boiling
point is reached when the temperature reaches a constant value. It is a good
idea to have students plot data as it is collected; this allows them to
visually determine the boiling point from a graph of their data.
10. Once boiling point is reached (defined as
the point where the water temperature no longer increases, but remains constant
for 5 minutes), remove thermometer from water and turn off hot plate or Bunsen
burner. Allow time for water to cool before dumping it out of the beaker.
Days 3-5: Water Boiling Point Measurement
1. Repeat steps 2-10 from day 2. Students
should not need to graph data following the practice run, as they should now
have an understanding of the boiling point.
2. After data have been collected on days
3-5, each group should average the water boiling point for the three days. If
data are to be submitted The International Boiling Point Project website, a
class average boiling point, initial water temperature, and room temperature
should be calculated.
Extensions:
Students should make the connection between air pressure
and boiling point. At sea level, there are more molecules in a given volume of
air (higher air density) than at higher elevations. At higher air density, more
energy (more heat – higher temperature) is required for water to change phase
from a liquid to a gas, meaning more energy is required for water molecules to
evaporate. Have them practice with the simulator:
Assessment Plan:
Students should create a data graph (x-axis: time since
the hot plate or Bunsen burner was turned on, y-axis: water temperature) that
clearly presents the results of their experiment from day 2. The graph clearly
illustrates when the boiling point is reached, as the temperature will increase
until the boiling point is reached, at which temperature will remain constant
(within approximately 0.2 °C). Students should create a data table that clearly
presents the results of their experiment from days 3-5, including boiling point
temperature, initial water temperature, air temperature, weather conditions, and
average measurements for each variable (calculated from data collected by the
entire class). Each individual student should use the average measurements to
test their own hypothesis. Students should write a brief “lab report” that
provides interpretation of the results and discussion of results in relation to
their hypothesis.
[1] Anne Helmenstine. "Boiling Point of Water -
What Temperature Does Water Boil?." 2010. 16 Jan. 2014 <http://chemistry.about.com/od/howthingswork/f/boiling-point-of-water.htm>
[2] (2009). Boiling and Freezing points of pure and
salty water - Physics Van. Retrieved January 16, 2014, from http://van.physics.illinois.edu/qa/listing.php?id=1457.
[3] (2005). The International Boiling Point Project -
The Center for Innovation in ... Retrieved January 16, 2014, from
http://www.ciese.org/curriculum/boilproj/.
[4] "Determination of Boiling Point of Water -
OLabs - Amrita ... - YouTube." 2012. 16 Jan. 2014 <http://www.youtube.com/watch?v=jsoNJFv6i9E>
[5] "'Experiments' - Evaporation, boiling and
Bubbles - YouTube." 2011. 16 Jan. 2014 <http://www.youtube.com/watch?v=fnXjQW1LVLQ>
[6] (2010). Boiling Point - YouTube. Retrieved January
16, 2014, from http://www.youtube.com/watch?v=dx4XOYpj1_k.
[7] "Forecast Error - National Weather
Service." 2007. 16 Jan. 2014 <http://forecast.weather.gov/MapClick.php>
[8] "Melting and Boiling - Harcourt School." 16 Jan. 2014 <http://www.harcourtschool.com/activity/hotplate/>
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