Measurements

September 20th-23rd

Types of Measurements

• Mass- triple beam balance • Length- ruler/meter stick• Volume- volumetric flask/ ruler • Temperature- thermometerc• Time- stopwatch• Density- triple beam balance and ruler/flask

Types of Units• All measurements are measured using metric

system…• Units fall into two categories: – Base- units produced by solely one measurement• Mass• Temperature• time

– Derived- units produced by the combination of more than measurement • Volume- (length X width X height)• Density – (mass/volume)

A few reminders for taking measurements…

• Always estimate one digit• The number of digits written will be the

number of sig figs the measurement has• Always include the appropriate units based on

the measurement taken.• Convert the units if needed…

Basic Conversions

• Once measurements have been taken sometimes they must be converted from one to another.

• Ladder of Conversions allows us to go from one unit to another.

Conversion ladder

Practice using the ladder

• Using the ladder complete the following conversions:

• 506 mm = ___ dm

• 7.4 kg = ____ mg

• .34 L = ____ cL

Dimensional Analysis

• A step by step process that allows you to complete basic conversions

• Requires use of a conversion factor:– A conversion factor is a fraction that allows you to

either multiply by a factor of 10 or divide by a factor a 10.

– Conversion factor allows all units to cancel so you are left with the units you are trying to reach.

Using Dimensional Analysis Example:

4.5 L = ____ mL Steps: 1)Write out the number you start with including units.2)Leave space, put an equal sign and write the units you are going to.3)Insert conversion factors

4. 5 L X = ____mL

Conversion factors for L and mL100ml or ___1L__ 1 L 1000mL

A few practice:

1) 25 g = ___kg

2) 32 cm = ___mm

3) 2.3 g/mL = ___ g/L

Regular Solid• Cube:

Length3

• Rectangular Prism: Length x width x height

• Cylinder:π r2 h

Irregular Solid

Mass/volume•Volume = volume displacement

Pour water into a graduated cylinder or beaker, add substance and measure how much the water changes.

Determining Density of a liquid

Density Practice: • What is the density of a piece of wood that has a

mass of 25.0 grams and a volume of 29.4 cm3?

• A cup of gold colored metal beads was measured to have a mass 425 grams. By water displacement, the volume of the beads was calculated to be 48.0 cm3. Given the following densities, identify the metal.

Gold: 19.3 g/mLCopper: 8.86 g/mL

Bronze: 9.87 g/mL

Honors density problem:

• A little aluminum boat (mass of 14.50 g) has a volume of 450.00 cm3. The boat is place in a small pool of water and carefully filled with pennies. If each penny has a mass of 2.50 g, how many pennies can be added to the boat before it sinks?

Homework

• Chapter Review- Tests – Monday September 28th- A – Tuesday September 29th- B

Density Pre-lab: Lab conducted September 28th and 29th