Chemistry June 20, 2008 1st Qtr

Scientific Measurements

Measurement - consist of a number and its corresponding unit
i.e. 2 minutes, 8000 millilitres, 4.5 light-years

I. English System of Measurement
i.e. inches, miles, gallons, pounds

II. Metric System, SI
> common language of all scientists

INCONVENIENT UNITS to use at all times
* meter, second, gram, etc.
Why?
i.e.
length of hair - meter is is too long for measuring length of hair
distance from Manila to Laguna - meter is too short for this distance

Metic Prefix - can make the base unit larger or smaller by adding the prefix before the base unit

link to metric prefix


3 units of Temperature:

1) Degrees Fahrenheit (°F)
2) Degrees Celsius
3) Kelvin (K)

Formulae for conversion

°C to °F (°F = 9/5 °C + 32 )

K to °C ( K = °C +273)

°F to °C (°C = 5/9 [°F-32])

i.e. a recipe calls for roasting a cut of meat at 350 degrees Fahrenheit. What is the temperature in (a) Celsius and (b) Kelvin?

formula for (a) : °F to °C (°C = 5/9 [°F-32])
F = 350

C = 5/9 (350 - 32)
C = 5/9 (318)
C = 176.67


formula for (b) : K to °C ( K = °C +273)

K = 176.67 + 273
K = 449.67

2) O C to F
F = 9/5 C + 32
F = (9/5) 0 + 32
F = 0 + 32
F = 32

3) 300 K to F
K = 300

K = C +273

300 = C + 273
300 - 273 = C
27 = C

F = 9/5 C + 32

F = 9/5 (27) + 32
F = 48.6 + 32
F = 80.6

4) 273 K to C
K = 273

K = C + 273

273 = C + 273
273-273 = C
C= 0