Thermodynamics

Thermal Energy

• Thermal Energy (internal energy)-the total amount of energy in a substance-the sum of all its kinetic and potential energy. Thermal energy is the energy that a body has in the vibrations of its molecules

• element - a basic substance that can't be simplified (hydrogen, oxygen, gold, etc...)

• atom - the smallest amount of an element• molecule - two or more atoms that are

chemically joined together (H2, O2, H2O, etc...)

• compound - a molecule that contains more than one element (H2O, C6H12O6, etc...)

STATES OF MATTER

• The Four States of Matter

• Solid• Liquid• Gas• Plasma

• Element is a pure chemical substance consisting of a single type of atom distinguished by its atomic number, which is the number of protons in its atomic nucleus

• Atoms are defined by their proton count. • The element hydrogen is made from atoms

containing a single proton and a single electron. If you change the number of protons an atom has, you change the type of element it is.

• Atomic Mass- The protons and neutrons account for almost all of the mass of an atom. Atomic mass is typically calculated by adding the number of protons and neutrons together, ignoring the electrons because of their small size.

• Proton mass - 1.007316 u = 1.67262178 × 10-27 kilograms

• Neutron mass-1.008701 u = 1.674927351(74)×10−27 kg

• Carbon = 6 protons and 6 neutrons = 12.00 u

• Nitrogen

Atom Molecule

Single particle 2 particles

N (Nitrogen) N2 ( 2 Nitrogen)

Mass 14 u Mass 28 u

What is the mass in kg for N2 ?

Proton mass - 1.007316 u = 1.67× 10-27 kilogramsNeutron mass-1.008701 u = 1.67 (74)×10−27 kg

• Mass (28u) ( 1.67 x 10-27) = 4.68 x 10-26 kg

STATES OF MATTERSTATES OF MATTER

Based upon particle arrangement

Based upon energy of particles

Based upon distance between particles

Kinetic Theory of Matter

Matter is made up of particles which are in continual random motion.

STATES OF MATTERSOLIDS

-Organized structure-Strong chemical bonds holds the particles together.  -No kinetic energy -Hard to compressParticles of solids are tightly packed, vibrating about a fixed position. •Solids have a definite shape and a definite volume. •No kinetic energy

STATES OF MATTERLIQUID

Molecules have no organization

Liquids have an indefinite shape and a definite volume.

Particles of liquids are tightly packed, but are far enough apart to slide over one another.

Liquids have an indefinite shape and a definite volume.

Slow

Low KE

STATES OF MATTERGAS

Particles of gases are very far apart and move freely.

Gases have an indefinite shape and an indefinite volume.

Volume occupy all space available

Highs KE and move about randomly

Temperature and pressure depended on KE

Gasses have the weakest chemical bond.

STATES OF MATTER

SOLID LIQUID GAS PLASMA

Tightly packed, in a regular pattern

Vibrate, but do not move from place

to place

Close together with no regular arrangement.Vibrate, move

about, and slide past each other

Well separated with no regular arrangement.

Vibrate and move freely at high

speeds

Has no definite volume or shape and is composed

of electrical charged particles

TEMPERATURE

TEMPERATURE Temperature is operationally

defined to be what we measure with a thermometer.

A measure of the average kinetic energy of the particles of a substrate.

Indicates relative internal energy within a body.

Again, temperature is the quantity measured by a thermometer.

Celsius-centigrade system The scale is used in most of

the world. The Celsius scale does not have an upper limit, but it does have a lower limit. The lowest possible temperature is -273.15 º C.

º degree symbol means relative to (water)

Fahrenheit scale The Fahrenheit scale is used

in the United States .

thus one degree on the Celsius scale is 1.8 times larger than one degree on the Fahrenheit scale

Absolute zero ( -273ºC ) molecules move slowly as

the temperature lowers. At absolute zero, the molecules almost sop, which means that they cannot be cool anymore. Absolut zero can be approach it can never be attained

No Temprature, No Pressure, thus No KE

Kelvin scale The Kelvin scale is a system

that uses absolute zero as its zero point. The abbreviation for zero Kelvin is 0 K. In this scale there are no negative temperatures. A degree on the Kelvin scale (called kelvin) has the same size as a Celsius degree.

Conversions

Celsius -Fahrenheit Water freezes at 32° F and boils

at 212° F. The Fahrenheit scale has different size of degree. Example 180 degrees make up the span from freezing to boiling point of water. Only 100 degree Celsius are needed for this span on Celsius scale.

100/180=5/9 is the ration of Celsius and Fahrenheit.

Conversion

(°C ) (9/5) + 32 = °F

(°F - 32) ( 5/9) = °C

Conversions

Kelvin <-> Celsius A degree on the Kelvin scale

(called kelvin) has the same size as a Celsius degree.

Kelvin = Celsius + 273.15

T(K)=T(ºC)+273.15

Thermal Equilibrium and the Zeroth Law

Thermal equilibrium Systems are in thermal

equilibrium when they have the same temperature

Thermal equilibrium occurs when two bodies are in contact with each other and can freely exchange energy.

The Zeroth law of Thermodynamics

If two systems, A and B, are in thermal equilibrium with each other, and B is in thermal equilibrium with a third system, C, then A is also in thermal equilibrium with C.

Thermometers

Thermometers It is based on the fact that

any two systems placed in thermal contact (meaning heat transfer can occur between them) will reach the same temperature (Thermal equilibrium.)

Thermal Energy Transfer

Conduction

Convection

Radiation

Thermal Energy Transfer Conduction

Conduction- is a form of thermal energy transfer that occurs through collisions between particles of matter. Conduction occurs as higher energy particles collide with and jostle neighboring lower energy particles, gathering kinetic energy form one particle to the next. Conduction transfers heat through material directly, through contact

Convection Convection – the transfer of

thermal energy due to physical movement of material. Convection transfers thermal energy (heat) in a fluid (liquids and gasses). Thermal energy moves form a higher-temperature region to a lower-temperature region.

Buoyancy often drives the fluid’s motion

Radiation Radiation-the transfer of

thermal energy in the form of electromagnetic waves ( light and infrared). The electromagnetic waves carry the energy. Electromagnetic radiation comes form accelerating electric charges.

Ex - SUN