Chemistry - Scientific Notation, Uncertainty, and Units of Measurement

Scientific Measurement Pledge

You must estimate one digit in all of your measurements for science

You can NOT estimate more than one digit

• digit on the far right is the estimated digit

Measurements

a quantity that has both a number and a unit

examples are:

• height

• age

• temperature

Uncertainty in Measurement

calculating uncertainty helps us know which digit is estimated

a digit that must be estimated is called uncertain

• a measurement always has some degree of uncertainty

Calculating Uncertainty

1. figure out what each mark on the measuring tool represent

2. take the number from step 1 and divide it by two

3. The uncertainty of that measuring tool is ± the quotient 

Meniscus

the curvature of liquid in a graduated cylinder

• caused by capillary action

• measure the bottom of the meniscus when calculating the volume of a liquid

Water Displacement

the phenomenon where an object submerged in water pushes the water out of the way, causing the water level to rise

• we can find an object’s volume by measuring the initial and final water levels in a graduated cylinder

Scientific Notation

a method of representing very large or very small numbers

a number is written as the product of two numbers: a coefficient and 10 raised to a power

• the coefficient is always a number greater than or equal to one and less than ten

• the exponent is an integer (positive integer = indicates how many times the coefficient must be multiplied by 10) (negative integer = indicates how many times the coefficient must be divided by 10)

Multiplying Scientific Notation

• multiply the coefficients

• add the exponents

Dividing Scientific Notation

• divide the coefficients

• (exponent in the numerator) — (exponent in the denominator)

Adding or Subtracting Scientific Notation

the exponents must be the same integer

• to do this, rewrite the coefficient

• example: (5.4×10³)+(8.0×10²) = (5.4×10³)+(0.80×10³)

Units of Length

• meters (m)

• kilometers (km)

• centimeters (cm)

• millimeters (mm)

Units of Volume

• liters (L)

• milliliters (mL)

• cubic centimeters (cm³)

Units of Mass

• kilograms (kg)

• grams (g)

• milligrams (mg)