Heat and Temperature

Temperature

Objective Define temperature in terms of the average

kinetic energy of atoms or molecules Convert temperature readings between the

Fahrenheit, Celsius, and Kelvin Describe heat as a form of energy transfer

Temperature and Energy

All particles in a substance are moving Particles have kinetic energy Temperature is the measurement of

average kinetic energy More kinetic energy the higher the

temperature

Thermometers

Use a simple physical property Most objects expand when their

temperature rises Ordinary thermometers will use mercury or

colored alcohol which expand and contract as temperature changes

• Caused by exchange of energy from thermometer and surroundings

– Why not water?

Thermometer variations

Dial thermometers with pointers Use 2 types of metals for coil to control

arrow – coil unwinds lowering pointer

Digital thermometer Measures temperature by change in

current Change in temperature changes electric

current-it all has to do with kinetic energy

Fahrenheit, Celsius and Kelvin

Fahrenheit Scale Used in U.S. but no place else Unit of measure is degrees- oF Water freezes at 32 oF Water boils 212 oF

Celsius (centigrade) Used in most countries and in science Water freezes at 0 0C Water boils at 100 0C Difference between freezing and boiling is

divided in 100 equal parts called degrees Celsius-0 C

Degree of Celsius is 2x the degree of Fahrenheit

More Equations:

Celsius-Fahrenheit Conversion Equation

• Fahrenheit temp=(9/5 x Celsius temp) + 32.0

• Tf = 9/5t + 32.0

Fahrenheit-Celsius Conversion Equation

• Celsius Temp = 5/9(Fahrenheit temp -32.0)• t= 5/9 (Tf - 32.0 )

Kelvin Scale Based on absolute zero

• The point where the energy of an object cannot be any lower

• Equal to -273.13 0 C• Lowest point on Kelvin Scale is 0K

• No negative numbers

Another equation (it easy)-Celsius to KelvinKelvin temp = Celsius temp + 273

T= t + 273

Math Skills page 328Practice questions

• Page 328 page 1-4

Relating Temperature to Energy Transfer as Heat

Why does ice melt in your hand? Ice has lower temperature than your hand Molecules in ice are moving slower than

molecules in hand Energy transferred from fast moving

molecules of hand to slower ice molecules Ice molecules speed up which increases

kinetic energy – causes ice to melt

The transfer of energy between the particles of 2 objects due to temperature difference between the 2 objects is called

•The transfer of energy goes from hotter to colder•What happens if you hold a hot water bottle?•What happens when drinks are put into ice?•What happens when you put your hands together?

Page 330 Questions 1-7