1. 1 Energy and Heat It Is All Around You…

2. 2 You have heard the word “ENERGY” before, but how is it defined by a scientist? Energy is defined as “the ability to do work.” the hot steam that comes from a hot iron, and this glass that is about to fall on the floor. the electricity that comes into our homes, the food we eat, …the sunlight that warms your face, Energy is all around us. Examples include…

3. 3 Five Main Forms of EnergyNuclear Electricity Chemical Heat Mechanical (Atoms In Motion)

4. 4Mechanical Did you know that a waterfall has energy? Mechanical energy is defined as “matter in motion.” How do these examples demonstrate mechanical energy?

5. 5Chemical A substance is changed from one form to another. This energy released is in the bonds of atoms.

6. 6 Electrical (examples) Static electricity is released when lightning strikes. Electrical current is the movement of electrical charges. Chemical  Electrical Mechanical  Electrical

7. 7Nuclear There is energy at the atomic level. Energy Nuclear Fission Splitting the Atom

8. 8 Heat Heat is a form of ENERGY. Atoms are constantly moving. Heat is produced with the motion of atoms.

9. 9 Heat and Kinetic Energy Energy of Motion at the Atomic Level The atoms to the left demonstrate kinetic energy because they are moving. All atoms move (vibrate) except at absolute zero (-273 o K or -459 o F) where ALL motion stops. The more heat is produced, the higher the temperature. The faster the atoms move, the more heat is produced. For more on absolute zero go to: http://www.colorado.edu/physics/2000/bec/temperature.html

10. 10Conduction Ouch! …is the transfer of heat by the direct contact of particles of matter. The heat of the boiling liquid directly contacts the metal spoon and causes the spoon to transfer the heat to the hand.

11. 11 Air above the flame heats and expands and you feel the heat transferring into your hand. Cool water is pushed down As the heated water rises… Convection …is the transfer of heat by the actual motion of a fluid (liquid or gas) in the form of currents. The heated water rises as the cooler water is pushed down. The water that was pushed down is then heated and … then rises pushing the now cooler water down. This causes a current in the water.

12. 12Radiation …is heat transfer by electromagnetic waves. MATTER is not necessary for this transfer of heat. A common type of radiation comes from the sun. Examples include – Ultraviolet Visible Light Color spectrum – (ROYGBIV) Infrared

13. 13 Specific Heat The definition of specific heat is a substance’s ability to absorb heat. –This chart lists specific heat for various materials. SubstanceSpecific Heat Air Aluminum Copper Glass Ice (-20 to 0 0 C) Iron Mercury Ocean Water Water Wood 0.25 0.22 0.09 0.20 0.50 0.11 0.03 1.00 0.42 0.93

14. 14 Calculating Heat Energy: The formula: Heat loss or gain (Q) = Mass x  Temperature(T) x Specific Heat of the material (C) In short: Q = M x  T x C

15. 15 The Problem How much heat is needed to raise the temperature of 4 grams of aluminum 5 o C? Q = M x  T x C Q = M =  T= C = ? 4 g 5 o C 0.22 (from the chart) We need to figure out “Q” so we can leave the formula as it is: Q = M x  T x C 4g X 5 o C X 0.22 cal/g o C = 4.4 calories

16. 16 A 10 gram sample of a “mystery substance” gained 16.5 calories of heat when the temperature changed 15 o C. What is the specific heat of that substance? Look on the chart to determine the “mystery substance.” Q = M =  T= C = 16.5 calories 10 g 15 o C ? We don’t want mass and temperature on the right, so we can divide both sides by “M x  T” and cancel. Q = M x  T x C M x  T M x  T … you are left with Q M x  T = C We need to figure out “C” so we have to rearrange the formula. We want “C” to be alone on one side of the equal sign. Q = M x  T x C Let’s do the math 16.5 Cal. 10g x 15 o C = 0.11 cal/g o C If you look on the chart, you find out that’s iron!

17. 17 Potential Energy… Kinetic Energy… can also be called stored energy (energy is not being used). Example: the chemical energy stored in a stack of coal. can also be called energy of motion. When this locomotive engine uses the coal, it becomes energy of motion.

18. 18 Potential Energy Which glass has the most potential energy? Because the glass on the left is on a higher table, it has more potential energy. It will hit the floor with more energy than the one on the right. What is the source of potential energy in this example? The Pull of Gravity

19. 19 Heat vs Temperature Heat is Energy –Movement of atoms –Total kinetic energy of molecular motion in a substance. –Depends on speed, number (size and mass), and type of particles. –http://fs.sdsu.edu/pisces/WeatherKit/Lesson05.php#3http://fs.sdsu.edu/pisces/WeatherKit/Lesson05.php#3 – Temperature is a measure of Energy –Thermo =heat –Meter = to measure –Measurement of the average kinetic energy of molecular motion in a substance. –Does not depend on the speed or type of particle.