Heat and temperature

April

Vocabfor review

Celsius condensation conduction convection energy transfer evaporation freezing gas heat joules Kelvin kinetic energy law of conservation of energy liquid melting molecular level phase phase change potential energy pressure radiation solid specific heat sublimation temperature thermal energy work

Vocab for mastery

law of entropy thermal equilibrium thermodynamics

Non-academic vocab

closed system co-efficient component contraction decay deterioration disorder efficient expansion macroscopic medium / media relate directly

Engagement

http://jersey.uoregon.edu/vlab/Thermodynamics/index.html

*Thermal equilibrium: the state in which two bodies in physical contact with each other have identical temperatures.

*

Engagement

EXPLORATION

• Virtual Lab – Determination of Specific Heat• The amount of heat required to raise the

temperature of a solid body depends on its change in temperature (DeltaT), its mass (m), and an intrinsic characteristic of the material forming the body called specific heat (cp). The heat is calculated from the equation

• q = cp x m x ΔT

• Historically, heat (q) was measured in terms of calories. The calorie was defined as the amount of heat required to raise the temperature of 1 gram of water by 1 ⁰C from 14.5 ⁰C to 15.5 ⁰C at 1 atmosphere pressure. With this definition, the specific heat of water is 1.00 cal/(g · ⁰C ). The use of the calorie began before it was established that heat is a form of energy and 1 calorie is equivalent to 4.18 J. The joule (J) has become the more favored unit in recent years. Thus, the units for cp that we will use are J/(g · ⁰C ). The specific heat of water is then 4.18 J/(g · ⁰C ).

• PURPOSE:• To apply the experimental methods of

calorimetry* in the determination of the specific heat of a metal.

• *calorimetry: an experimental procedure used to measure the energy transferred from one substance to another as heat.

• PROCEDURE:• Perform three trials for EACH material. Record the mass of

the sample, the initial temperature (T1), the final temperature (T2), and the energy absorbed (in joules).

• Vary the mass of the sample and the length of time heating for each trial with a given material. In other words, no two trials for a given material should use both the same mass and the same flame exposure times.

• At the end of each trial, hit the "Reset" button to prepare for the next trial.

• http://www.sciencegeek.net/VirtualLabs/SpecificHeatLab.html

RESULT

Material___________

Trial #1 Trial #2 Trial #3

Mass of object, m (g)

g g g

Initial temperature of object (T1)

⁰C ⁰C ⁰C

Initial temperature of object (T2)

⁰C ⁰C ⁰C

Energy absorbed (Joules)

J J J

• Observation and data:

result

• CALCULATIONS: Show your work! You will repeat the calculations three times for each material you test.

• Calculate the temperature change, ΔT, (T2 - T1).

• Calculate the specific heat, Cp. Cp = q ÷ m ÷ ΔT

Material______________

Trial #1 Trial #2 Trial #3

ΔT, (T1 – T2) ⁰C ⁰C ⁰C

Cp j/(g · ⁰C) j/(g · ⁰C) j/(g · ⁰C)

Temperature scales

• Celsius and Fahrenheit scales• Tf=9/5 Tc + 32

• Celsius and Kelvin (or absolute) scales• T= Tc + 273.15

Phase changes

• Leg “A”: temp. of ice changes as energy is added.

• Leg “B”: temp. of ice does not change. Instead, the nature of the ice changes. The ice-and-water mixture remains at this temp. until all of the ice melts.

• Leg “C”: the water’s temp. increases as energy is added.

• Leg “D”: temp. stops rising and the water turns into steam.

• Leg “E”: the steam’s temp. increases.• During Leg “B” and Leg “D,” the energy added

or removed changes the internal energy of the substance without changing its temp. These changes in matter are called phase changes.