IB+DP+Topic+3+Thermal+Physics

3.1 Thermal concepts Evidence through experimentation: Scientists from the 17th and 18th centuries were working without the knowledge of atomic structure and sometimes developed theories that were later found to be incorrect, such as [|phlogiston] and ‍perpetual motion capabilities‍. Our current understanding relies on statistical mechanics providing a basis for our use and understanding of energy transfer in science. (1.8)
 * // Nature of science: //**

• Molecular theory of solids, liquids and gases • Temperature and absolute temperature • Internal energy • Specific heat capacity • Phase change • Specific latent heat
 * // Understandings: //**

//** Applications and skills: **// • Describing temperature change in terms of internal energy • Using Kelvin and Celsius temperature scales and converting between them • Applying the calorimetric techniques of specific heat capacity or specific latent heat experimentally • Describing phase change in terms of molecular behaviour • Sketching and interpreting phase change graphs • Calculating energy changes involving specific heat capacity and specific latent heat of fusion and vaporization

//** Aims: **// • Aim 3: an understanding of thermal concepts is a fundamental aspect of many areas of science • Aim 6: experiments could include (but are not limited to): transfer of energy due to temperature difference; calorimetric investigations; energy involved in phase changes

//** Data booklet reference: **// • Q = mc D T • Q = mL

media type="youtube" key="uYYEX5v5a9A" width="560" height="315" Can you trust your senses? 3 different temperatures of water
 * Changing States of Matter Published on 13 Feb 2013 youtube.com**

Kelvin is a temperature scale in a measure of motion/KINETIC ENERGY of gas particles. It is also known as thermodynamic temperature scale. °C + 273.15 = K

ex) What temperature of Kevin is same as 49°C =

__ 322.15 __ K

The absolute zero of temperature is –273.15 °C or 0 K. This is the lowest temperature any substance can have. At absolute zero of temperature, the substance has minimum internal energy. =Specific Heat Capacity= Research at least 5 values of specific heat capacities for some common substances that we see in our everyday life. 1. water and sea water 2. copper 3. aluminium 4. iron 5. gold 6. coconut oil 7. land/soil/marble
 * Absolute zero = 0 K**

What do you think? The specific heat capacity of sea water is __ greater __ than that of the land and so __ more __ heat energy is needed to heat it up by the same amount as the land and so it takes __ longer. __ It takes __ longer __ to cool down as well.

Each metal and each material have a different rate of heating. Gold heats up 7 times faster than aluminium. That means that everything has their own specific heat capacity and the SHC of gold is 7 times __ less/lower __ than the __ Specific Heat Capacity __ of aluminium.

The heat energy needed to raise the temperature of a substance by 1 K is called the ** HEAT CAPACITY ** of the object. The SPECIFIC HEAT CAPACITY of a substance is the heat needed to raise the temperature of 1 Kg of the substance by 1 K (or by 1 o C) Specific heat capacity is given the symbol c. The units for c are J/(kg K) or J/(kg o C).

m = mass of substance. Unit( J kg -1 K -1 or J kg -1 o C )

 * //Applications of Specific Heat Capacity in daily life//**
 * 1) Using water as heat agent in a heating system
 * 2) Cooling system of a car engine.
 * 3) Designing a cooking pot
 * body: aluminum - low specific heat capacity - heats up quickly
 * base: copper - low specific heat capacity - heat up very quickly
 * handle: plastic - high specific heat capacity - insulator
 * from** [|heatmozac.blogspot.com]

Image for **[|USGS Water Science School]**
 * What is the reason for fish's comment?**

//**Applications of Specific __Latent__ Heat Capacity**//
 * 1) We can cool down the temperature of canned drinks by adding several cubes of ice in a bucket of drinks.- A large amount of heat is absorbed when ice melts and this lowers the temperature of the drinks.
 * 2) Water has a large specific latent heat of vaporization. This property enables steam to be used for cooking by the method of steaming. When steam condenses on the food, the latent heat is released directly onto the food enables the food to be cooked at a faster rate.
 * 3) Always be very careful when opening the lid of a pot when the water in it is boiling. Water has a large specific latent heat of vaporization. When steam condenses on the skin of your arm, the very large amount of latent heat released can cause a serious burn.
 * 4) Our bodies feel cool after sweating. This is because latent heat of vapourisation is absorbed from the body when sweat evaporates. As a result, the body is cooled by the removal of heat.

The ** specific latent heat of fusion ** of a solid substance is the heat required to change one kilogram of it from solid to liquid without any temperature change. The ** specific latent heat of vaporization ** of a liquid substance is the heat required to change one kilogram of it from liquid to vapour without any temperature change. source from [|arenahanna.wordpress.com]
 * The temperature does not change even though heat is being ** absorbed by the solid particles **. This is because the heat absorbed does not increase the kinetic energy of particles but is used to overcome the force of attraction between the particles.
 * The temperature does not change even though heat is being ** absorbed by the liquid particles. ** This is because the heat absorbed does not increase the kinetic energy of particles but is used to overcome the force of attraction between the particles.

**In your notebook, take notes on Importance of Specific Heat Capacities - Please do not copy the below.**
The specific heat of a substance is an important physical property because it tells us the suitability of a given substance for a specific purpose. Aluminium vessels are used in cooking because aluminium is a light metal. Hence, for a given volume, its thermal capacity will be less than that of vessels made of steel of same volume. The high specific heat of water explains why land close to a large pond of water is likely to have a milder climate than land without a pond close by. Because of high specific heat, water on the land gets heated slowly. Land near the pond also gets heated slowly. For the same amount of heat, dry land gets heated quickly to a much higher temperature. Soil is a poor conductor, prevents the heat from going deep into the ground. Hence, the heat causes a quick rise in temperature on dry land. For same reasons, land areas far from water-cool off much faster than land near large bodies of water.

SPECIFIC LATENT HEAT OF FUSION OF ICE PRACTICAL - Always a good idea to look at this before submitting your work. media type="youtube" key="hC_NKgHF1MM" width="560" height="315" Heat capacity and Specific Heat Capacity Doc Physics

Latent Heat of Fusion of Ice (3rd Jan. 2012)
Aim: To determine the latent heat of fusion of ice.

Apparatus: goggles, balance, calorimeter, thermometer, stirring rod, 2 to 6 ice cubes, 200mL water, 100mL graduated cylinder, 250mL beaker, paper towel, balance

Method: 1. Fill the beaker with about 150mL water. Heat the water on a hot plate. You will need water that is about 10oC above room temperature. 2. Place the plastic foam cup and stirring rod on the balance together. Record the combined mass. 3. Keep the cup and stirring rod on the balance. Carefully fill the cup about half-full with the warm water. Record the combined mass. Take care not to pour water on the balance! 4. Calculate and record the mass of the warm water. Put the calorimeter on the lab counter. Stir the water carefully with the stirring rod and record the temperature. 5. Immediately add 2 to 4 ice cubes that have been dried with paper towels. 6. Stir slowly until all the ice has melted. Record the temperature of the water in the cup; it should be about 10oC below room temperature. If you need to bring the temperature down, you can add more dried ice cubes. Make sure to get a final temperature reading of the water. 7. Obtain and record the mass of the cup, stirring rod and cool water.

Results: Conclusion and evaluation:
 * || Mass(g) || Temperature( o C or K) ||
 * Calorimeter and stirring rod ||  || x ||
 * Calorimeter, stirring rod, and warm water ||  || x ||
 * Warm water ||  ||   ||
 * Equilibrium temperature ||  ||   ||
 * Calorimeter, stirring rod, and cold water ||  || x ||
 * Ice added ||  || x ||
 * = Energy lost ||= Energy gained ||= Latent heat of fusion of ice ||

Q = mcΔT m w or mi = mass/kg : mass of water or ice ΔT = o C c = SHC /Jkg -1o C -1 :4200 in water l f = SLH fusion/J kg -1 Q = Thermal Energy /J c w = 4200 +50 Jkg -1o C -1

Decrease in temperature of water = 1. Increase in P.E. of ice so it melts + Increase in K.E. of ice of it melted Heat lost by water = Heat gained by ice to melt + Heat gained by melted ice. {Q=mc __ΔT__ } = {mlf} + {m i cΔT} Decrease from start T to mixture of mw +mi m w c w (T max - T min ) = m i l f + m i c w (T min - 0)

[|Sample Data analysis, Conclusion and Evaluation] from theibguide.com

media type="youtube" key="lTKl0Gpn5oQ" width="560" height="315" The Phase Change of Water song by Mr. Edmonds Specific latent heat of Fusion and Vaporization

Thermal capacity[C]is the amount of thermal energy required to raise the temperature of a body by 1K/1 o C.
 * Thermal Capacity ** [C] ** : **

Q = Thermal energy absorbed in J.
C = heat capacity, Unit ( J K -1 or J o C )

Thermal capacity depends on the __ mass __ and the __ material __ of the object.
Q>0: Heat is added to system Q<0: Heat is removed from system

3.2 Modelling a gas Collaboration: Scientists in the 19th century made valuable progress on the modern theories that form the basis of thermodynamics, making important links with other sciences, especially chemistry. The scientific method was in evidence with contrasting but complementary statements of some laws derived by different scientists. Empirical and theoretical thinking both have their place in science and this is evident in the comparison between the unattainable ideal gas and real gases. (4.1)
 * // Nature of science: //**

//** Understandings: **// • Pressure • Equation of state for an ideal gas • Kinetic model of an ideal gas • Mole, molar mass and the Avogadro constant • Differences between real and ideal gases

//** Applications and skills: **// • Solving problems using the equation of state for an ideal gas and gas laws • Sketching and interpreting changes of state of an ideal gas on pressure– volume, pressure–temperature and volume–temperature diagrams • Investigating at least one gas law experimentally

//** Aims: **// • Aim 3: this is a good topic to make comparisons between empirical and theoretical thinking in science • Aim 6: experiments could include (but are not limited to): verification of gas laws; calculation of the Avogadro constant; virtual investigation of gas law parameters not possible within a school laboratory setting


 * // Data booklet reference: //**

Kinetic Model of an Ideal Gas
Theoretical model which particles accurate predictions: Gas is made of trillions of tiny particles. They obey Newton's laws Intermolecular forces are negligible. Molecules are spherical Negligible volume(vol. tiny compared to separation) Random motion Perfectly elastic collisions(conservation of K.E) Time taken for collision is negligible. All particles in the gas have the same mass. ||
 * **Assumption:**


 * Temperature:** Absolute temperature is proportional to average K.E of particles.


 * Pressure:**When one particle collides with container it bounces back elastically. It has a change in momentum (as direction changes) so there is a force on it (Newton's 2 Law). There is an equal and opposite force on the wall. If you add together forces of all particles(microscopic), there is pressure(microscopic). F = ΔP/ Δt

If volume decreases then collisions are more frequent so total force is greater, If temperature increases, the particles move faster so... 1. The average collision has greater force 2. Collisions more frequent Both these factors increase pressure. PHET Ideal Gas Properties Simulation media type="custom" key="11997291"
 * Conclusions:**

1. Make a constant Volume Plot a graph
 * Pressure || Temperature/K || Uncertainties ||
 * 2 || 300 ||  ||
 * 1.9 || 275 ||  ||
 * 1.70 || 258 ||  ||
 * 1.61 || 238 ||  ||
 * 1.35 || 200 ||  ||
 * 1.18 || 175 ||  ||

2. Make a constant Pressure Plot a graph
 * Temperature/K || Volume/unit(nm) || Uncertainties ||
 * 300 || 9.6 ||  ||
 * 269 || 8.4 ||  ||
 * 246 || 7.8 ||  ||
 * 217 || 7 ||  ||
 * 174 || 5.8 ||  ||
 * 143 || 4 ||  ||

3.In a constant Temperature(separate P-V device) Embed picture 1st trial 2nd trial
 * Pressure/atm || Volume/unit(ml) || Uncertainties ||
 * 0.98 || 40.9 ||  ||
 * 1.11 || 36.6 ||  ||
 * 1.2 || 34.1 ||  ||
 * 0.85 || 44.9 ||  ||
 * Pressure/atm || Volume/unit(ml) || Uncertainties ||
 * 0.70 || 54.7 ||  ||
 * 0.90 || 44.7 ||  ||
 * 0.99 || 41.2 ||  ||
 * 1.47 || 28.5 ||  ||
 * 1.60 || 26.3 ||  ||
 * 1.75 || 24.2 ||  ||

**The state of a gas**
This depends on few variables; p, V, n, T related by pV = nRT(equation of state for an ideal gas) 2 variables are delined by a line e.g. V= kT 3 variables are delined by a surface e.g. pV/T = nR when n is fixed, then p, V, T lie on the surface.

These 3 graphs show the gas laws for different values of the constant variable. graph 1 p-V graph 2 V-T graph 3 p-T

Isothermal (same temperature) Image from antonine education e.g. The lines on the pV graph are called isothermal.(lines of constant temperature)

Isochoric(=Isovolume) Isobaric media type="youtube" key="TqLlfHBFY08" width="560" height="315" Ideal Gas Law Practice Problems Tyler DeWitt youtube.com


 * Homework**: Make notes and graph on the 3 gas laws(on one side of A4).

Image from Hyperphysics [|Ideal Gas questions] from physicsLAB

__**Equation of State**__ from the gas laws.
For a fixed mass of gas, p1V1/T1 ∞ p2V2/T2, This leads to pV = nRT, The constant n is the number of moles, not the properties of the gas. 1 mole of any gas has the same volume. Therefore, R is a universal gas constant, where R = 8.314 J -1 K- 1 mol -1

z(mass) of He 2 : 4, => n=8/4=2mol pV = nRT V = (2 x 8.314 x 293)/101,000 = 0.048 m 3
 * e.g. What is the volume of 8g HE at STP.(Standard pressure and temperature: p=101,000 Pa, T= 20 o C)?**

Prescribed practical #2:
Either to i nvestigate the effect of pressure on the volume of gas or to investigate the effect of temperature on the volume of gas using the ideal gas equation. Apparatus: Rubber band, aluminum foil, ice, water bath, anti bumping granule, Ruler, opened end monometer, glass tube, thermometer, conical flask, beaker, mercury plug,retort stand, Bunsen burner. [|Sample Ideal Gas Law lab] from www.uccs.edu =[|The ideal gas] from physics.bu.edu=

For a low-density/high-temperature gas, we neglect the long-range intermolecular attraction and treat the short-range repulsion as perfect elastic. This leads to:

The Ideal Gas Model

 * 1) The gas consists of a large number of identical molecules.
 * 2) The volume occupied by molecules themselves is negligible compared to the volume of the container.
 * 3) Molecules move at constant speed in random directions between collisions.
 * 4) <span style="font-family: &#39;Lucida Grande&#39;,Geneva,Arial,Verdana,sans-serif; font-size: 20px;">Molecules experience forces only during collisions that are elastic and instantaneous.

**Ideal Gas Law:** P V = n R T where P is pressure, V is volume, n is the number of moles, T is the absolute temperature, and R = 8.31 J/(mol K) is the universal gas constant. This can be written in terms of N, the number of molecules, instead. Using N = nN A, where N A is Avogadro's number, we obtain: where the Boltzmann constant k = 1.38 x 10-23 J/K is the universal gas constant divided by Avogadro's number. Intuition for the Ideal Gas Law:
 * P V = nN A (R/ N A ) T || = N k T ||
 * <span style="font-family: &#39;Lucida Grande&#39;,Geneva,Arial,Verdana,sans-serif; font-size: 20px;">The pressure of an ideal gas is proportional to 1/V ---squeezing a gas leads to higher pressure.
 * <span style="font-family: &#39;Lucida Grande&#39;,Geneva,Arial,Verdana,sans-serif; font-size: 20px;">Pressure is caused by molecules colliding with the container walls. This leads to P ∝ T . As T → 0, the thermal energy → 0. Then there are no collisions with container walls and therefore no pressure.

[|Molecular constants] from HyperPhysics The average translational [|kinetic energy] of any kind of molecule in an ideal gas is given by KE = (3/2)kT per molecule = (3/2)RT per mole

What is the root mean square velocity of a nitrogen (N 2 ) molecule in this classroom? KE = (3/2)kT = (1/2)mv 2 = (3/2)kT

v 2 = 3kT/m

v 2 = 3(1.38 x 10 -23 J/K) (273 +20)K / {(28u) x (1.66 x 10-27 kg/u)} v=510 m/s media type="youtube" key="M2ZeA2U8Ri0" width="560" height="315" <span style="background-color: #ffffff; font-family: Roboto,arial,sans-serif; font-size: 20px;">IB Phyiscs: Applying the Ideal Gas Law & the Boltzman constant

**Real Gases**
When a real gas is compressed the forces are no longer negligible and it doesn't obey the gas laws. Real gases can liquefy. Ideal gases never liquefy. An ideal gas is very reasonable approximation.

**IB DP Thermodynamic systems - old syllabus**
This is an ideal gas in which we can consider changes to the physical macroscopic properties the gas can gain/lose thermal energy and can do work.

Thermodynamics
About movement of heat and work done. Simplest case; an ideal gas in a piston.

**__The surroundings__**
This is anything outside the system where energy can be transferred to.

**__Heat ΔH__**
ΔH is to the heat transferred as a result of temperature difference, to/from surroundings. The sign indicates the direction of hear flow.

__**Work ΔW**__
ΔW is the work done by a gas on its surrounds, or the work done on a gas by the surroundings.(Indicated by the sign) Image from umist

w= F x d (p = F/A, F = pA) w = pA x d w = pV

__**Internal Energy ΔU**__
ΔU, internal energy, only of the ideal gas not as a result of its position or movement as a system.

**Internal energy**
In an ideal gas there are no intermolecular forces. i.e. no PE For internal energy of an ideal gas is total random KE of particles.

To move the piston, we need a force F = P x A Work done an gas, W = F x d W= pAΔd, AΔd =ΔV(change in volume) Work done; __W = pΔV__

Work done on gas = p(V2 -V1) This is area under graph. The work done on/by a gas is measured by area under pV graph. This true for all processes. If volume decreases, work done on the gas. If volume increases, work done by the gas. Work done by gas is positive

This is based on the conservation of energy. Lf heat energy is added to a system, then one, two or both of the following will happen. - Internal energy will increase - Work done by the gas increases
 * First Law of Thermodynamics**

i.e. ΔQ = ΔU + ΔW, Heat added = internal energy + work done by the gas +ΔQ: Heat added to system -ΔQ: Heat removed/(taken away) from system +ΔU: Internal energy increases(Temperature increases). +ΔW: The system(gas) __DOES work ON__ the surroundings(Expands). -ΔW: The system(gas) __HAS work done ON it__(Compresses).


 * reference: Entropy is a measure of how disorganises something is.
 * [[image:nothingnerdy/IB_Thermal_formulas.png]] ||

Useful files for this unit:
[|Heat transfer exercise questions] [|PBS Space Time] Published on 26 Apr 2017 ||
 * media type="custom" key="29107501" || media type="custom" key="29590307" ||
 * Entropy (Order and Disorder) Energy BBC w/ Jim Al-Khalili HD || =[|Are You a Boltzmann Brain?] | Space Time=

<span style="display: block; display: inline !important;">[|Star Stuff] Published on 31 Jan 2017