Honors Chemistry Unit I - Power Point 8

Temperature Conversions

Sections 1.7

Temperature ScalesTemperature ScalesThree Systems for Measuring Temperature

• FahrenheitFahrenheit

• CelsiusCelsius

• KelvinKelvin

Anders Celsius1701-1744

Lord Kelvin(William Thomson)1824-1907

Gabriel Fahrenheit1686-1736

The Three Major Temperature Scales

Notice that 1 kelvin = 1 degree Celsius1 kelvin = 1 degree Celsius

Converting Between Scales

K C C K

C F F C

+ 273.15 273.15

5 C 9 F 32 F + 32 F

9 F 5 C

T T T T

T T T T

Calculations Calculations Using Using TemperatureTemperature

• Generally require temp’s in Generally require temp’s in kelvinskelvins

• T (K) = t (˚C) + 273.15T (K) = t (˚C) + 273.15

• Body temp = 37 ˚C + 273 = 310 KBody temp = 37 ˚C + 273 = 310 K

• Generally require temp’s in Generally require temp’s in kelvinskelvins

• T (K) = t (˚C) + 273.15T (K) = t (˚C) + 273.15

• Body temp = 37 ˚C + 273 = 310 KBody temp = 37 ˚C + 273 = 310 K

Temperature ConversionsTemperature Conversions

A person with hypothermia has a body A person with hypothermia has a body temperature of 29.1°C. What is the body temperature of 29.1°C. What is the body temperature in °F? temperature in °F?

°F °F = = 9/5 (29.1°C) + 329/5 (29.1°C) + 32

= = 52.4 + 3252.4 + 32

= = 84.4°F84.4°F

Learning CheckLearning Check

The normal temperature of a chickadee is The normal temperature of a chickadee is 105.8°F. What is that temperature in °C?105.8°F. What is that temperature in °C?

1) 73.8 °C 1) 73.8 °C

2) 58.8 °C2) 58.8 °C

3) 41.0 °C3) 41.0 °C

Answer: 41 °C °C

Learning Check

Pizza is baked at 235 °C °C . What is that in °F?

1) 455 °f1) 455 °f

2) 350°C2) 350°C

3) 400°C3) 400°C

Answer: 455 °FAnswer: 455 °F

Exercise

At what temperature does C = F?

• Since °C equals °F, they both should be the same value (designated as variable x).

• Use one of the conversion equations such as:

• Substitute in the value of x for both TC and TF. Solve for x.

Solution

C F5 C

32 F9 F

T T

Solution

C F5 C

32 F9 F

T T

5 C 32 F

9 F

x x

40

So 40 C = 40 F

x