1 / 17

16.1 Thermal Energy and Matter

16.1 Thermal Energy and Matter. In the 1700’s, heat was believed to be a fluid, caloric , which flowed between objects. Ben Thompson, Count Rumford, disproved this in 1798. He made cannons and noticed that brass heated while drilling (boiled water) but cooled when drilling stopped.

cynara
Download Presentation

16.1 Thermal Energy and Matter

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 16.1 Thermal Energy and Matter • In the 1700’s, heat was believed to be a fluid, caloric, which flowed between objects. • Ben Thompson, Count Rumford, disproved this in 1798. He made cannons and noticed that brass heated while drilling (boiled water) but cooled when drilling stopped. • The conclusion was heat was not a separate piece of matter, but related to the drilling due to friction.

  2. Work and Heat • The transfer of thermal energy from one object to another because of a temperature difference is heat. • Heat flows spontaneously from hot objects to cold objects (“stealing” heat).

  3. Temperature • A measure of how hot or cold an object is compared to a reference point is temperature. • Absolute zero is 0 Kelvin. • Temperature is related to the average kinetic energy of the particles in an object due to their random motions through space. • Hot objects move faster, and heat is transferred by collisions. • High energy loses in collisions, and low energy gains in collisions (parked car that is hit moves).

  4. Thermal Energy • Thermal energy depends on the mass, temperature, and phase (solid, liquid, or gas) of an object. • Thermal energy is the total potential and kinetic energy of all the particles in an object. • Thermal energy depends on mass (longer to heat bucket of water than a droplet).

  5. Phases of Matter: Solid • Definite shape • Definite volume • slow-moving

  6. Phases of Matter: Liquid • Definite volume • Indefinite shape • Faster moving than solid • Capillary action- can go against gravity • Surface tension- the surface can hold (Red Rover)

  7. Phases of Matter: Gas • Indefinite shape • Indefinite volume • Faster than liquid • Moves erratically

  8. Thermal Contraction and Expansion • A balloon on a cold day will shrink, and tires deflate. This is due to the gas moving more slowly and exerting less force, or thermal contraction. • A balloon on a hot day could pop due to thermal expansion, or an increase in volume due to increase in temperature. • Thermal expansion occurs when particles of matter move farther apart as temperature increases. • Gases expand the most. • Thermometers depend on the expansion on alcohol (red fluid rises) or coil unwinding for a stove.

  9. Specific Heat • You do not get pizza burn from the crust, but the crust is the same temperature as the cheese that can burn the roof of your mouth. • This is because crust and cheese have different specific heats. • Specific heat is the amount of heat needed to raise the temperature of one gram of a material by one degree Celsius. • The lower a material’s specific heat, the more its temperature rises when a given amount of energy is absorbed by a given mass. • Water has a high specific heat of 4.18 J/gdegreeCelsius.

  10. Specific Heat • Q = mcT • Q = heat (J) • M = mass (g) • C = specific heat (J/gdegree Celsius) • T = change in temperature (degrees Celsius)

  11. Specific Heat problems • An iron skillet has a mass of 500 g. The specific heat of iron is 0.5 J/gdegreesCelsius. How much heat must be absorbed to raise the temperature 90 degrees Celsius? • Q = mcT • Q = (500)(0.5)(90) • Q = (250)(90) • Q = 22500 J, or 22.5 kJ

  12. Specific Heat Problems • How much heat would raise 100 g of water 100 degrees Celsius? • Q = mcT • Q = (100)(4.18)(100) • Q = (418)(100) • Q = 41800 J or 41.8 kJ

  13. Specific Heat Problems • How much heat is absorbed by 70 g of iron that goes from 25 degrees Celsius to 125 degrees Celsius? • Q = mcT • Q = (70)(0.5)(125-25) • Q = (70)(0.5)(100) • Q = (35)(100) • Q = 3500 J or 3.5 kJ

  14. Specific Heat Problems • An aquarium transfers 1200 kJ heat to 75,000 g of water. What is the increase in temperature? • Q = mcT • 1200000 = (75000)(4.18)T • 1200000 = 313500T • T = 4 degrees Celsius

  15. Specific Heat Problems • To release a diamond, a jeweler must heat a 10 g ring with 24 J of heat. What was the temperature change? • Q = mcT • 24 = (10)(0.2)T • 24 = 2T • T = 12 degrees Celsius

  16. Specific Heat Problems • What mass of water will change 3 degrees Celsius when 525 J of heat is added to it? • Q = mcT • 525 = (m)(4.18)(3) • 525 = (m)(12.54) • M = 42 g

  17. Measuring Heat Changes • A calorimeter is an instrument used to measure changes in thermal energy. • A calorimeter uses the principle that heat flows from a hotter object to a cooler object until both reach the same temperature. • Thermal energy of the burning food is absorbed by the surrounding water. • Water is stirred for even distribution of heat. • The calorimeter is made of an insulator.

More Related