Day 12• Lab Day 13 – Measurements• Day 14 Quiz on Units and Measurements• Day 15 – Lab Density• Day 16 – Quiz Scientific Notation and Sig Figs

Units of MeasurementWhy do we need a “standard unit of Measurement?– Report Data that can be reproduced

Base Units– Time = Seconds (s)– Length = meter (m)– Mass = kilogram (kg) – Volume = space occupied by an object• Liter (L)

Derived Units

Now What are the units for the following?– Mass = ?• Grams or g

– Volume = ?• mL or cm3

= Combination of base unitsExample: Density• Density = Mass Divided by Volume– How would we write this? Use symbols.

Derived Units Continued

or

Now What are the units for the following?– Mass = ?• Grams or g

– Volume = ?• mL or cm3

Now… Insert them into the formula!

Density

So… Density is the Ratio of Mass to Volume.

Determining Volume• Here is an odd shaped Object…

• How would you find the volume if you couldn’t take any measurements?

• Water displacement that’s how…• What happens when you get into a bath tube

that is filled to the top with water?– That’s right it over flows! Why..

Water displacement

Water Displacement• Let’s take our object• And a graduated Cylinder filled with some water• … enough to cover the object• … but not completely filled (remember what

happened to the bath tube!)

Water Displacement and Volume• What would happen if we placed our object• … into the graduated cylinder?

• The Water level starts at..– 46 mL

• Ends at 66 mL• What’s the difference…– 20 mL– That’s the volume of the object

Using the Density formula answer the following questions.

• A piece of metal with a mass of 147g is placed in a 50mL graduated cylinder. The water level rises from 20mL to 41mL. What is the density of the metal?

• What is the volume of a sample that has a mass of 20g and a density of 4 g/mL?

Units• All measurements start with the base unit– Length is m or meters– Volume is L or liters– Mass is g or grams

• How ever… what if the object is less than the base unit?

• Let’s look at length or meters (m)1 meter

Units continues

• Each unit (m, L, g) is broken down into parts of 10• Lets break this meter stick into 10 parts

1 meter

1 2 3 4 5 6 7 8 9 10

• Each part is 1/10th of a meter• Each part is called a decimeter or dm• So… what is the length of this nail?– 4 dm or 4 decimeters

• This is 1 dm

• This is 1 cm• This is 1 mm

Prefixes Used with SI Units

Look at your chart on page26

Examples

Centimeter = ?– 100th of a meter or .01 or 10-2

Kilometer = ?– 1000 meters or 10 3

Millimeter– 1000th of a meter / or .001 / or 10-3

TemperatureWhat is the SI Unit of Temperature?– Kelvin (K)• 273 K = freezing point of water• 373 K = boiling point of water

What’s the difference between the two?– 100 degrees

What is Celsius?– Temperature measurement based on 0o – 100o C

We will always convert Celsius to Kelvin, unless told not to.

Converting Kelvin to CelsiusConvert - Celsius to Kelvin– oC (what you measured) + 273 K = Kelvin

Convert – Kelvin to Celsius– oK (what you measured) – 273 K = oCelsius

Convert the following to Kelvin– 357o C– -39o C

Convert the following to Celsius– 266 K– 332 K