Here is a paper of my students about Thermology. The work was made using self-made instruments and completely in English(spontaneously)
Groups members: Linda Greggio, Linda Bertin, Silvia Verza, Sara Zerbetto, Caterina Fortin
ABSTRACT
Thinking to the experiments that we realized with the struments supplied by our school’s scientific laboratory and the ones that our physic teacher Alfonso D’Ambrosio gave us, we could verify experimentally the validity of the basic law of calorimetry
Q=cm∆T
in which Q is the heat energy, m the mass, c the specific heat and ∆T the change of temperature.
The results we obtained during these experiments, next to the mistake’s discussion caused by heat loss lead no to can clude that the heat energy is directly proportional to the change in temperature, which instead is inversely proportional to the mass of object or substance taken to heat energy variation, absorbed by the object with less temperature.
Materials used:
- classic bulb (not LED), scientific thermometer, polystyrene as a thermal insulation?, chronometer, rose cardstock, black cardstock;
- aluminum rod, stall Rod, scientific candle, “church” candle, scientific thermometer;
- hot plate laboratory, 2 beckers, water, scientific thermometer, chronometer
First experiment:
| Distance | 2.5 cm | 5 cm | 3.5 cm |
| Time | 1 min | 1 min | 1 min |
| Tf | 42°C | 28°C | 30.5°C |
We calculated the temperature varying the distance between the scientific thermometer and the classic bulb. We observed that:
Ti=initial temperature=25°C
Tf=final temperature
Because of the heat lass this is an exponential and not an inverse proportional that can explain Boltzmann’s Law:
P=eσAT4 → T4 α 1/r2 → T2 α 1/r
Where P is the power radiated from an object; e is the emissivity of the object’s area; σ is the Boltzmann’s constant and A the object’s area.
| Distance | 2.5 cm |
| Time | 1 min |
| Temperature | 37°C → less than without it(42°C) |
If we put an polystyrene a black cardstock we observed that:
↓
This is because black absorbs all wavelengths of lights
| Distance | 2.5 cm |
| Time | 1 min |
| Temperature | 41°C → near the temperature without it (42°C) |
If the cardstock is pink we observed that
↓
This is because pink it’s similar to white that repels light because it reflects all the colors
Second experiment
| Aluminum=a | Steel= s | |||
| distance (between the candle and the thermometer) | 2,5 cm | // | 2,5 cm | // |
| time | 1 min | 2 min | 1 min | 2 min |
| Tf | 70°C | 100°C | 100°C | 165°C |
We calculated the temperature of 2 rods heated by a scientific candle, varying the material of the rod. We observed that:
Ti: 23 °C
The temperature of the steel rod gets higher than the one of the aluminum rod. Both of them are good thermae conduct(a’s C = 880 J/Kg·K; s’s C=500J/Kg·K) but steel disperses less heat aluminum , that disperses it immediately.
| Distance | 2,5 cm | 5 cm | 10 cm | |||
| Time | 1 min | 2 min | 1 min | 2 min | 1 min | 2 min |
| Tf | 100 °C | 165 °C | 30 °C | 50 °C | 24 °C | 26 °C |
Than we calculated the temperature of the same rod of steel, heated by a scientific candle put at different distance. We observed that:
Ti: 23 °C
So we notice that the distance and the variation of temperature are inversely proportional according with the law of conduction of Fourier:
Q=λ A ∆T ∆t/L
where λ is thermal conductivity,
A is the section of the rod and L is the distance
Third experiment
| mass | 50 g | // | 150 g | // |
| time | 1 min | 2 min | 1 min | 2 min |
| Ty | 27°C | 32°C | 23°C | 25°C |
We calculated the temperature of the water in a becker on a hot peat of laboratory (preheated to 200°C) varying the water ‘ s mass we observed that :
Ti = 21°C
This prove that mass is inversely proportional to the variation of temperature, the same thing established by the basic law of the calorimetry:
m = Q/c ∆T
We conclude by saying that if we observe nature we can notice that is regulated by the physic‘s earns that are in our book. So physic‘s earns are the theoric result of what happens every day to things that around us. In final we think that with the help of the physic we can live in a better way and we can also preview the future.
Linda Greggio, Linda Bertin, Silvia Verza, Caterina Fortin, Sara Zerbetto