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 Measurement Why 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 cm 3 = Combination of base units Example: 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 cm 3 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 Each part is 1/10 th 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 = ? – 100 th of a meter or.01 or Kilometer = ? – 1000 meters or 10 3 Millimeter – 1000 th of a meter / or.001 / or 10 -3

Temperature What 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 0 o – 100 o C We will always convert Celsius to Kelvin, unless told not to.

Converting Kelvin to Celsius Convert - Celsius to Kelvin – o C (what you measured) K = Kelvin Convert – Kelvin to Celsius – o K (what you measured) – 273 K = o Celsius Convert the following to Kelvin – 357 o C – -39 o C Convert the following to Celsius – 266 K – 332 K