Slide 1 / 112 Slide 2 / 112 8th Grade Thermal Energy 2015-10-09 www.njctl.org Slide 3 / 112 Temperature, Heat and Energy Transfer · Temperature · Thermal Energy Click on the topic to go to that section · Energy Transfer · Specific Heat · Thermodynamics and Energy Conservation
Slide 4 / 112 Temperature Return to Table of Contents Slide 5 / 112 Sensing Temperature Which of the following do you think is colder, the ice cream or the tea? It is easy to tell if an object is hot or cold by touching it. How hot or cold something feels is related to temperature, but only provides a rough indicator. Slide 6 / 112 What is Temperature? To understand temperature, remember that all matter is made of molecules that are in constant motion. What kind of energy do they have if they are in motion? Even the molecules in this solid pencil are vibrating relative to a fixed position. The water molecules in this glass are in constant random motion.
Slide 7 / 112 Temperature and Kinetic Energy Temperature is directly proportional to the average kinetic energy of an object's molecules. The more kinetic energy molecules have, the higher the temperature. clip: Indiana University Slide 8 / 112 Thermal Expansion As the temperature of a substance increases, its molecules pick up speed and gain kinetic energy. This increase in kinetic energy causes the molecules to spread farther apart and the substance expands. image: National Oceanography Centre Slide 9 / 112 Thermal Contraction As the temperature of a substance decreases, its molecules slow down and lose kinetic energy. What do you think this decrease in kinetic energy causes? Compare it to what we said about warm molecules.
Slide 10 / 112 Thermal Expansion Watch this demo of a metal ball and ring to see thermal expansion. Click here to watch a metal ball and ring demo. Explain what happened to make the ball not fit. How did the person make the ball fit again? What is happening in terms of the kinetic energy of the molecules in the ball? Slide 11 / 112 Thermal Expansion The change in volume a material experiences due to temperature changes depends on the type of material and the amount of temperature change. Click here to watch what happens when things expand at different rates. Slide 12 / 112 1 All matter consists of molecules that are constantly in motion. True False
Slide 12 (Answer) / 112 1 All matter consists of molecules that are constantly in motion. True Answer False True [This object is a pull tab] Slide 13 / 112 2 Temperature is the measure of the average __________ of a substance's molecules. A mass B speed C spacing D kinetic energy Slide 13 (Answer) / 112 2 Temperature is the measure of the average __________ of a substance's molecules. A mass B speed Answer D. kinetic energy C spacing D kinetic energy [This object is a pull tab]
Slide 14 / 112 3 After a thunderstorm, the sun comes out and warms a puddle of water that is on the sidewalk. As the puddle of water gets warmer, its molecules: A speed up B slow down C take up less space D gain kinetic energy Slide 14 (Answer) / 112 3 After a thunderstorm, the sun comes out and warms a puddle of water that is on the sidewalk. As the puddle of water gets warmer, its molecules: A speed up B slow down Answer A. speed up C take up less space D. gain kinetic energy D gain kinetic energy [This object is a pull tab] Slide 15 / 112 Measuring Temperature Determining the kinetic energy associated with a substance's molecules would be difficult. Thermometers are used as a more practical way to measure an object's temperature. A thermometer usually consists of a small amount of liquid, such as mercury or colored alcohol, in a narrow tube.
Slide 16 / 112 Temperature Scales Three scales of temperature commonly used are: Fahrenheit: used primarily in the United States · Celsius: 1 degree Celsius= 3.2 degrees Fahrenheit · Kelvin: is based on absolute zero, the lowest temperature · something can have. Slide 17 / 112 Temperature Scales Slide 18 / 112
Slide 19 / 112 Slide 20 / 112 Temperature Conversions The lowest temperature an object can have is the lowest value on the Kelvin scale 0 K! One Kelvin is equal to one degree on the Celsius scale. To convert from Celsius to Kelvin use the following equation. K= °C +273 Example: Water boils at 100 °C. What is the boiling temperature of water in Kelvin? Click the pot of boiling water for the answer! The answer is 373 K. Just add 273 to 100 °C! Slide 21 / 112 4 The coldest temperature ever recorded was -89.2°C in Antarctica on July 21, 1983. Convert this temperature to °F.
Slide 21 (Answer) / 112 4 The coldest temperature ever recorded was -89.2°C in Antarctica on July 21, 1983. Convert this temperature to °F. Answer -128.6 °F 184 K [This object is a pull tab] Slide 22 / 112 5 The coldest temperature ever recorded was -89.2°C in Antarctica on July 21, 1983. Convert this temperature to Kelvin. Slide 22 (Answer) / 112 5 The coldest temperature ever recorded was -89.2°C in Antarctica on July 21, 1983. Convert this temperature to Kelvin. Answer -128.6 °F 184 K [This object is a pull tab]
Slide 23 / 112 6 If you measure the temperature of an object, its Kelvin temperature will be larger than its Celsius temperature. A never B always C sometimes D not enough information to determine Slide 23 (Answer) / 112 6 If you measure the temperature of an object, its Kelvin temperature will be larger than its Celsius temperature. A never Answer B. always B always C sometimes D not enough information to determine [This object is a pull tab] Slide 24 / 112 7 The hottest recorded temperature ever recorded was about 329 K in Death Valley, California on July 10, 1913. What is this temperature in Celsius?
Slide 24 (Answer) / 112 7 The hottest recorded temperature ever recorded was about 329 K in Death Valley, California on July 10, 1913. What is this temperature in Celsius? This is a more challenging question in that it requires students to come up with the "equation" for converting Kelvin to Celsius which is the Answer reverse of converting Celsius to Kelvin. Have a student show their work on the board or explain how they got the answer. 56°C [This object is a pull tab] Slide 25 / 112 8 The temperature in deep space is about 3 Kelvin. What is this temperature in °F ? Slide 25 (Answer) / 112 8 The temperature in deep space is about 3 Kelvin. What is this temperature in °F ? Answer about -454 °F [This object is a pull tab]
Slide 26 / 112 Thermal Energy Return to Table of Contents Slide 27 / 112 Energy in Matter Molecules in matter possess Kinetic Energy. Do you remember why molecules have kinetic energy? Which drink is likely to have molecules with MORE kinetic energy? How is kinetic energy related to an object's temperature? Slide 28 / 112 9 The hotter an object, the faster the molecules in it move. True False
Slide 28 (Answer) / 112 9 The hotter an object, the faster the molecules in it move. True False Answer TRUE [This object is a pull tab] Slide 29 / 112 Energy in Matter Molecules in matter also possess Potential Energy. This energy is based on the attractive and repelling forces that all molecules exert on each other. Recall molecules are made up of individual atoms. Each atom contains a positively charged nucleus and negatively charged electrons outside the nucleus. Proton Electron - + + - Neutron Slide 30 / 112 10 Protons and electrons A attract each other Electron Proton B repel each other C other
Slide 30 (Answer) / 112 10 Protons and electrons A attract each other Electron Proton B repel each other C other Answer A [This object is a pull tab] Slide 31 / 112 11 Opposite charges attract and like charges A attract each other B repel each other C other Slide 31 (Answer) / 112 11 Opposite charges attract and like charges A attract each other B repel each other C other Answer B [This object is a pull tab]
Slide 32 / 112 Energy in Matter When atoms and molecules interact, electrons are attracted to protons and repelled by other electrons. Atoms in a molecule are "bonded" together because their positively charged nuclei and negatively charged electrons are attracted to each other. Repelling force between electrons and electrons Attractive force between positive and negative charges Slide 33 / 112 Energy in Matter As the distance between atoms and molecules increases, the forces of attraction and repulsion decrease and the potential energy decreases. Slide 34 / 112 Energy in Matter The electrical potential energy is inversely proportional to the distance between molecules in matter. What does this inversely proportional relationship mean? The closer the molecules are together, the more potential energy they possess. The farther apart molecules are, the less potential energy they possess.
Slide 35 / 112 Energy in Matter Can you rank the amount of stored potential energy each state of matter has from highest to lowest? Think about the spacing between molecules! Solid, liquid, gas Slide 36 / 112 12 What two types of energy do molecules in matter possess? A Potential Energy B Kinetic Energy C Gravity D Thermal Energy Slide 36 (Answer) / 112 12 What two types of energy do molecules in matter possess? A Potential Energy B Kinetic Energy Answer A & B C Gravity D Thermal Energy [This object is a pull tab]
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