Chapter 1

1. Chapter 1 Matter, Energy, and Heat Basics

2. Matter • Any substance that has weight, mass, and occupies space. • Called an element when in the form of only one of the naturally occurring substances. • The atom: • Smallest particle of an element • Also considered to be matter • Can exist in any one of three physical states: • Solid, liquid, or gas

3. Solids • A substance that has definite volume and sufficient mechanical strength. • Exert all their forces in the downward direction toward either the surface on which they are resting or toward the earth.

4. A block of ice. A piece of wood. Solids

5. Liquids • Liquids have definite volumes, but do not have definite shapes. • The shape a liquid takes depends on the shape of the container that holds it.

6. Gases • Gases have neither definite volume nor definite shape. • Gas molecules have little attraction for each other; the gas will completely fill any vessel that contains it. • A gas exerts pressure in all directions against the walls of the container that holds it. • Gas laws determine the behavior of contained gases. • Boyle’s Law • Charles’ Law • Dalton’s Law

7. Gases Gas molecules exert pressure on the walls of a balloon.

8. Boyle’s Law • States that there is a definite relationship between the pressure and volume of a gas if the temperature is kept constant. • States that the pressure and volume of a gas are inversely related: • If the volume is decreased, the pressure will increase • If the volume is increased, the pressure will decrease

9. Charles’ Law • States that there is a definite relationship between the volume and temperature of a gas if the pressure is kept constant: • If the volume increases, the temperature increases • If the volume decreases, the temperature decreases • States that there is a definite relationship between the pressure and temperature of a gas if the volume is kept constant: • If the pressure increases, the temperature increases • If the pressure decreases, the temperature decreases

10. Dalton’s Law • States that the total pressure of a confined mixture of different gases is equal to the sum of the pressures of each gas in the mixture.

11. Dalton’s Law

12. First Law of Thermodynamics • States that energy cannot be created or destroyed, but can be converted from one form to another. • Simply stated, when one form of energy is generated, it is done so at the expense of another energy form.

13. Second Law of Thermodynamics • States that energy tends to degrade into low-level heat energy. • Heat energy is a byproduct of energy conversion and flows from a warmer substance to a cooler substance.

14. Work • Work is defined as the force exerted times the distance an object is moved. • Work occurs when a force moves a mass a certain distance: • If no movement results, no work is being done

15. Work

16. Power • Power is the rate of doing work, which is the amount of work per unit time. • The term horsepower (hp) is used to measure units of power: • During the 18th century, it was determined that a horse could lift 33,000 pounds to a height of 1 foot in one minute • Lifting 33,000 pounds to a height of 1 foot in 30 seconds would therefore be equal to 2 horsepower

17. British Thermal Units • Heat content is measured in British thermal units (Btu): • The Btu is defined as the amount of heat required to raise one pound of water 1 degree Fahrenheit • Raising the temperature of one pound of water from 68°F to 70°F would therefore require 2 Btu of heat energy

18. British Thermal Units

19. Temperature Scales • On the Fahrenheit temperature scale, water boils at 212 degrees and freezes at 32 degrees. • On the Celsius temperature scale, water boils at 100 degrees and freezes at 0 degrees. • Absolute zero, the temperature at which all molecular movement stops, is –460°F or –273°C • On the Rankine and Kelvin scales, absolute zero is at 0 degrees (–460°F).

20. Temperature Scales

21. Conduction • The heat transfers from one molecule to another within the substance. • Metallic substances conduct heat better than nonmetallic substances. • Good conductors of heat are typically good conductors of electricity.

22. Conduction

23. Convection • Convection is the transfer of heat by a flowing medium. • Heat transfer by convection takes place in liquids and gases, typically water and air. • The process of convection can be sped up by using fans or pumps.

24. Convection

25. Radiation • Heat that moves in the form of straight rays: • These rays produce heat when they come in contact with a surface without heating anything in their path

26. Radiation

27. Sensible Heat • Heat transfers that can be sensed with a thermometer: • Changing the temperature of air from 78°F to 72°F • Changing the temperature of water from 70°F to 75°F • Changing the temperature of steam from 220°F to 230°F • The state of the substance remains unchanged.

28. Latent Heat • In this process, heat is known to be added, but no temperature rise is measured. • It results in a change of state with no change in temperature: • Changing ice at 32°F to water at 32°F • Changing water at 212°F to steam at 212°F • Latent heat transfers cannot be measured with a thermometer.

29. Latent Heat

30. Pressure • The force that is exerted on the walls of a vessel. • Measured in force per unit area: • Atmospheric pressure is 14.7 pounds per square inch • Gauge pressure (PSIG) reads 0 psi at atmospheric pressure • Absolute pressure (PSIA) reads 14.7 at atmospheric pressure • Vacuum pressure is a reading below atmospheric pressure