Chemistry: Measurement, Dimensional Analysis, Calculations, Density

Qualitative Observations

Changes in color and physical state

Quantitative Measurements

Involve numbers based on the SI metric system

Stating a Measurement

In every measurement there is a number followed by a unit from a measuring device

Length SI Unit

Meter (m)

Mass SI Unit

Kilogram (kg)

Time SI Unit

Seconds (s)

Temperature SI Unit

Kelvins (K)

Derived SI Units

Produced by dividing or multiplying standard SI units;
area: m�
volume: m�
density: g/cm�

Kilo

Means 1000 of that unit; 1 kilometer is 1000 meters

Centi

Means 1/100 of that unit; 1 meter is 100 centimeters

Milli

Means 1/1000 of that unit; 1 Liter is 1000 militers

Scientific Notation

A way of expressing really big numbers or really small numbers; Consists of two parts: A number between 1 and 10, and a power of 10

Standard Form to Scientific Notation

1. Place the decimal point so that there is one non-zero digit to the left of the decimal.
2. Count the number of decimal places the decimal has "moved" from the original number This will be the exponent of 10
3. If the original number was less than 1, then the exponent is negative; if the original number was greater than 1, the exponent is positive

Scientific Notation to Standard Form

1. Simply move the decimal point to the right for positive exponent 10
2. Move the decimal point to the left for negative exponent 10. (Use zeros to fill places)

Fahrenheit

Based on human body; 212� (boiling point of water); 32� (Freezing point of water)

Celsius

Based on freezing and boiling point of water; 100� (boiling point of water); 0� (freezing point of water)

Kelvin

Based on the movement of particles; 373 (boiling point); 273 (freezing point);

Temperature Calculation

K = �C + 273
(Ex:) Body Temp. = 37�C + 273 = 310 K

Dimensional Analysis Steps

1. Identify starting and ending units
2. Line up conversion factors so units cancel out
3. Multiple all top numbers and divide by each bottom number
4. Check units and answer

Mass

Amount of matter (grams, measured with a balance); Always continuously the same

Weight

Force exerted by the mass, only present with gravity (pounds or Newtons; measured with a scale)

Density

The ratio of mass to volume; An important and useful physical property; mass (g)/volume (cm�)

Density Problem Solving Method

1. List the given information
2. State the unknown.
3. Write the formula, rearrange to solve for the unknown
4. Plug in numbers with units
5. Calculate and box answer with units

Volume

The amount of space occupied by an object

Volume Displacement

A solid displaces a matching volume of water when the solid is placed in water; (With liquids, substance with highest density will sink)

Accuracy

How close you are to the actual value; Depends on the person measuring

Absolute Error Equation

| measured value ? actual value |

% Error Equation

| measured value ? actual value | / actual value ? 100

Precision

How finely tuned your measurements are or how close they can be to each other; depends on measurement tool, determined by number of significant digits