Name: _____________________ | Class: Physics 214 |
SSN/ID: _____________________ | Section & Group: ____________ |
Objective
To determine the temperature of a liquid in degrees Fahrenheit and
Centigrade and to use the data to confirm the general relationship
between the two scales. Also, to determine the specific heat
of a metal object by measuring the amount of heat transferred from
that metal object to another, cooler body (of water). But the main
purpose of this lab is to elucidate the scientific method at work.
The idea is to make a guess (your hypothesis) based on some
underlying reasoning. Then, you perform an experiment to confirm or
deny that hypothesis and, based on the results, modify your guess
(your hypothesis), if necessary.
Equipment
See the Shockwave applets below. All data and calculations can be recorded using these sheets and your handout.
Definition
The main idea in this lab is to make a guess, or hypothesis,
for how long you think it'll take water to boil. What differentiates
Science from things like Astrology is the precision and testability of
our predictions. Both Astrologers and Physicists make predictions;
the only difference is that the Physicists' predictions are exact and
subject to objective verification.
You can make a theoretical prediction (or hypothesis) based on your theory (as opposed to an intuitive prediction based on no pre-knowledge and just whatever patterns you pick up on). You have learned enough science in this class to predict how much heat will be needed to raise the temperature of a certain mass of water from a certain temperature to boiling. The idea is to use this required amount of heat energy, and the rate at which heat energy is being pumped in, to predict how much time that process should take.
In order to get
water to boil, you have to raise its temperature to 100^{o}C
(at a pressure of 1 atmosphere).
If you know the amount of water you have, and the temperature it
starts out at (room temperature = 20^{o}C), then you can
determine just how much heat energy that mass of water will
need to get to boiling temperature. If you also know the
power, or the heating rate (remember, power is given in
units of [Watts] = [Joules/second]), you can determine just how
long it'll take to transfer the amount of heat you need to make the
water boil. This can be done by dividing the amount of heat
energy needed by the power, or heating
rate, (which is simply the amount_of_energy_transferred /
time). This is symbolized as:
[amount_of_heat_needed] [amount_of_heat_needed]
[time_required] = ----------------------- = ---------------------------
[power] [energy_transferred]/[time]
Procedure
Is there anything more exciting than watching water boil?
Energy Transferred [Joules] Heat Energy [calories] Q Heating Rate = Power = ------------------ = ---------- = ----------- = ---------- = --- time [sec] time [sec] t Q m c ΔT ==> Power = --- = -------- t t m c ΔT ==> t = ---------------- (Heating Rate)Please remember that Power (the heating rate) is just Energy/Time (either Joules/sec or calories/sec).
STOP! Record how you obtained your hypothesis on the fill-in sheet or handout and show them to your class supervisor before you proceed... |
Run | Water Amount [kg] |
Starting Temp [^{o}C] |
Heating Power [J/sec] |
Heat Energy Needed, Q [J] |
Time_{Hypothesis} [sec] |
Time_{Actual} [sec] |
Accuracy [%] |
1. | |||||||
2. | |||||||
3. |
The Shockwave Applet:
URL: http://ippex.pppl.gov/interactive/energy/boil_water.dcr
Questions
Notes
Please note that the applet shows mass in gm and shows the heating rate in two different units: both Joules/sec (Watts) and calories/sec.
Be consistent with your units! If Q is going to be in Joules, then m must be in kg, c in J/kg-^{o}C, and ΔT in centigrade degrees!
If Q is going to be in calories, then m will be in gm, c in calories/gm-^{o}C, and ΔT in centigrade degrees!