8th Grade Chapter 21 section 2 Heat (Part 1) 8th Grade Chapter 21 section 2

Do now…Conversion Practice The temperature of the science lab is 70 F. What is this temperature in Celsius? The temperature outside is 25 C. What is this temperature in Fahrenheit?

Thermal Energy (from yesterday) Potential Energy 1) Molecules in a material exert attractive forces on each other Ex: Gravity exerts an attractive force on a ball. 2) Molecules in a material have potential energy Ex: A ball above the ground has potential energy. 3) As molecules move closer together or farther apart, potential energy changes Ex: As a ball moves closer to or farther from Earth’s surface, its potential energy changes.

Explain the difference between thermal energy and heat Objectives Students will… Explain the difference between thermal energy and heat Describe 3 ways thermal energy is transferred

Heat and Thermal Energy Heat is the transfer of thermal energy from one object to another when objects are at different temperatures. The amount of thermal energy that is transferred when 2 objects are brought into contact depends on the difference in temperature between objects. 60 degrees 20 degrees 100 degrees 60 degrees

Conduction, Radiation and Convection Transfer of thermal energy by direct contact by collisions between particles Conduction Transfer of energy by electromagnetic waves Radiation Transfer of thermal energy by the movement of particles in a gas or liquid Convection

Classifying types of energy Transfer Complete each sentence using radiation, convection or conduction 1) The sun’s rays heat sand particles by ____________. 2) Cool air pushes in to replace warm, air flow by natural _____. 3) Body heat is transferred in to the air by _______. 4) Heat from the sun warms iced tea by __________. 5) A fan pushes air molecules by forced__________.

Mini Lab: Comparing Rates of Melting Purpose: Observe the effect of ice water on melting ice. Lab procedures/directions Complete lab worksheet. Questions?

Test signed by Thursday. For Next Time…. Read pgs. 616-617 Define convection, conductor, specific heat and thermal pollution on index cards. Test signed by Thursday.

8th Grade Chapter 21 Section 2 Mini Lab Heat (Part 2) 8th Grade Chapter 21 Section 2 Mini Lab

Watch Now… Review to heat vs. temperature

Identify materials as insulators or conductors Objectives Students will… Identify materials as insulators or conductors Complete mini-lab to observe convection

Thermal Conductors vs. Thermal Insulators - Conducts heat easily -gold and copper Material contains loosely held electrons Thermal Insulators - Does not conduct heat easily -materials do not contain loosely held electrons Depend on how strongly atoms hold electrons

Heat Absorption Specific Heat- is the amount of thermal energy needed to raise the temperature of 1kg of the substance by 1 degree C. More thermal energy is needed to change the temperature of a material with a high specific heat than one with a low specific heat. Ex: sand on a beach has lower specific heat than ocean water

Thermal pollution Thermal pollution- increase in the temperature of a body of water caused by adding warmer water. Effects: organisms need more oxygen and warmer water has less dissolved oxygen=organisms die due to low oxygen. Also organisms are more sensitive to chemical pollutants, parasites and disease. Reducing: Cooling warm water produced by factories, power plants and run off.

Mini Lab: Observing Convection Purpose: Observe convection process Lab procedures/directions Safety precautions (esp. wearing goggles during experiment!) Complete lab worksheet Proper clean up Questions?

For Next Time… Khan Academy Videos Converting F to C Comparing F and C Each lab group needs to bring a pair of oven mitts or pot holders.