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 Solids A block of ice.A piece of wood.

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 18 th 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