Welcome to Chemistry 116!Welcome to Chemistry 116!

Lab Safety and Proper Procedures

Labs 1

How to print out notes

• Go to file, click on print, look for print what change from slides to handouts; then adjust how many you want per page.

• Also change color to pure black & white.

Laboratory techniques –Part 1A and B

Objectives

1. Safety rules

2. Use equipment correctly

3. Sig figs

Ruler

• Units: meter, m

Reading a ruler

• 1. Do not start at the beginning of the ruler but at 0cm

• 2. Short lines are mm

• 3. The longer lines are cm

• 4. Your last reading should always be a guess or estimate!!

Measuring Volume of a regular shaped solid

• Basic unit is cubic centimeter cm3

• Volume = length x width x height     V (cm3 ) = L (cm) x W (cm) x H (cm)

The Beaker & the Graduated Cylinder

The graduated cylinder allows you to deliver precise volumes of liquid.

The beaker is useful for transferring solutions from one vessel to another.

Volume: is the amount of space occupied by an

object• Liquids are measured with a

graduated cylinder,.

• (standard); liter

1.   Notice that the surface of the liquid has a lens-shaped curve, the meniscus.

2. With the surface of the liquid at eye level, read the measurement at the bottom of the meniscus.

Measuring Volume in a Graduated Cylinder

Measuring Volume in a Graduated Cylinder

• Step 3: Determine the scale increment:To find the scale increment, subtract the values of any two adjacent labeled graduations and divide by the number of intervals between them.

The analytical Balance

• Greater accuracy then top loader:

• Never place chemical on the balance

• Always read to correct sig figs

• 0.0001 or 0.00001 grams is considered analytical.

Measuring Volume in a Graduated Cylinder

• Step 4: Estimate the uncertain digit and obtain a reading:

Chapter 1

Measurements

Significant Figures in Calculations

Size does matter!!

Significant Figures in Measurement

The numbers reported in a measurement are limited by the measuring tool

Significant figures in a measurement include the known digits plus one estimated digit

Get rid of all leading zeroes

Numbers with decimals Numbers with out decimals

All Significant Trailing zeroes not significant

Summary Sig Figs

State the number of significant figures in each of the following:

A. 0.030 m 1 2 3

B. 4.050 L 2 3 4

C. 0.0008 g 1 2 4

D. 3.00 m 1 2 3

E. 2,080,000 bees 3 5 7

Learning Check

Significant Numbers in Calculations

A calculated answer cannot be more precise than the measuring tool.

A calculated answer must match the least precise measurement.

Significant figures are needed for final answers from

1) adding or subtracting

2) multiplying or dividing

Adding and Subtracting

1. All we care about is the right of the decimal point!!!

a. Add the numbers together

b. The answer should have the same number of decimal places as the number with the least amount of decimal places

Adding and Subtracting

25.2 one decimal place

+ 1.34 two decimal places

26.54

answer 26.5 one decimal place

Learning Check

In each calculation, round the answer to the correct number of significant figures.A. 235.05 + 19.6 + 2.1 =

1) 256.75 2) 256.8 3) 257

B. 58.925 - 18.2 =1) 40.725 2) 40.73 3) 40.7

Solution

A. 235.05 + 19.6 + 2.1 =

2) 256.8

B. 58.925 - 18.2 =

3) 40.7

Multiplying and Dividing

Round (or add zeros) to the calculated answer until you have the same number of significant figures as the measurement with the fewest significant figures.

Learning Check

A. 2.19 X 4.2 = 1) 9 2) 9.2 3) 9.198

B. 4.311 ÷ 0.07 = 1) 61.58 2) 62 3) 60

C. 2.54 X 0.0028 =

0.0105 X 0.060

1) 11.3 2) 11 3) 0.041

Lab A and B

• Light a Bunsen burner correctly

• Parts A and B on page 11– Procedures on page 4 and 5

• Pre lab 1-15

• next week lab quiz 1

Bunsen burner

                     

Step 1

                       

Shut the air control.

Step 2

                         

Shut the gas control valve, and then open it

½ way

Step 3

Put safety goggles on!

                                                                       

            

Step 4

                                                      

Open the wall valve

.

Step 5

                            

Carefully light the burner.

Always use the striker at a 45 degree angle

Step 6

                         

The initial flame is low on oxygen and not very hot.

When the hole is closed and air is excluded from

mixing with the jet of gas, a yellow, luminous

flame is produced

Step 7

                             

Open the air control until the central blue cone

forms.

Step 8

                   

The hottest part of the flame is just above the central blue cone. (There is

no combustion inside the central cone.)

Step 9

                                                     

Be sure to close the wall valve when done.