General Laboratory Techniques Dry Lab Chemistry 1105

Meter stick ► are devices used to measure length ► Measurements' at home are inches, feet, and yard (in the U.S.) ► IN THE LAB Use SI unit : m (meter) Use SI unit : m (meter) 2

3 Meter stick 1 m = cm m = mm cm = mm Middle School Science!

4 Meter stick 1 cm = m mm = m Middle School Science!

Meter stick 5 What is your reading? 7.5 cm7.55 cm

Meter stick 6 What is your reading? 7.4 cm7.40 cm The last digit is counted as a significant digit

7 Meter stick How many decimal places can you read? A: m B: m The centimeter ruler is properly read to 0.01 cm by estimating between the smallest divisions. A: m B: m The last digit is counted as a significant digit

GRADUATED CYLINDERS ► In the lab, to transfer volumes of liquids from one container to another ► They are not highly accurate 8

GRADUATED CYLINDERS When you read, you read the bottom of the meniscus as shown. This is the concave line formed when liquid adheres to the sides of the container. This is called the meniscus. 9 Read the nearest tenth of a division.

BEAKERS ► approximate measurements ► They should never be used for accurate data collection ► Lots of sizes 10

► , -300 and 400 mL and, all are ±5% all are ±5% ► 100 mL actually has a volume range of error of 5% The volume would be between 95 mL and 105 mL 95 mL and 105 mL BEAKERS 11

Erlenmeyer Flasks ► approximate measurements ► They should never be used for accurate data collection ► Lots of sizes 12

Erlenmeyer Flasks ► , -300 and 400 mL and, all are ±10% ► 100 mL actually has a volume range of error of 10% The volume would be The volume would be between 90 mL and 110 mL 13

BURETTES ► long calibrated glass tubes with a stopcock ► The stopcock is for the dispensing of liquids from the delivery tube of the burette ► A burette is designed to very accurately dispense a volume of liquid 14

BURETTES ► Burettes come in various sizes, from 0.50 mL to 100mL, with the most common being the 50.0 mL. ► These are read to ±0.01 mL Read the nearest tenth of a division. 15

BURETTES 16 Estimate the reading of any scale to the nearest tenth division. The buret has 0.1 mL divisions, so we estimate the reading to the nearest 0.01 mL mL

THERMOMETERS: MERCURY / ALCOHOL ► measure the heat energy of a substance ► average kinetic energy in the substance 17

THERMOMETERS: ► Three units of measure  Fahrenheit (°F)  Celsius (°C)  Kelvin (K) ► Fahrenheit, Celsius is the measure most of the world uses. Kelvin is absolute temperature 18

Thermometers MERCURY / ALCOHOL ► Mercury thermometers have greater ranges ► Alcohol thermometers -10°C to 110˚C. Silver is mercury Red is alcohol When picking up a thermometer, pick it up by both ends. 19

Themometers ► Calibrated and checked for accuracy ► Never use a thermometer that has air bubbles in it 20

Themometers ► How to calibrate  Prepare an ice-water bath - this is a beaker filled with ice, and then water is added to the same level as the ice.  5 minutes in the ice bath, it reads 0°C If not, a correction is required. If not, a correction is required.  If water bath is reading 2.2˚C, then the correction factor is 2.2 when using this thermometer. A reading of 22.2˚C for the room temperature would mean that it is actually 20.0˚C 21

Balances ► A balance is a device that measures the mass of a substance ► NO chemical should be placed directly on the balance pan ► Always use a weighing paper or a weighing boat Click on video 22

Solutions and Chemicals Read the label 3 times  Before you reach for it  Before you use it  After you finish and put it away 23

Chemicals ► When you remove a lid or stopper from a container Close the container with the same top ► NEVER expect the next person to do this for you ► Do not leave it off, for the convenience of the next person...if they bump the bottle it will end up on you ► Video  24

Solids ► There are as many bottle types as there are chemicals 1. Loosen lid 2. Check to see if the chemical is loose. shake it before opening it and set it back down and open it. 3. If the chemical has hardened, open the container, and with a clean spatula, loosen the chemical. 4. Tilt the bottle so the cap is in the down position and the chemical falls into the cap. 5. Then tap the amount of the sample that you want into a weighing boat or weighing paper. 25

Solids ► Any excess chemical in the cap can be returned to the bottle ► Any chemical that has been placed on a weighing boat or paper has been contaminated and should be disposed of correctly as waste. 26

Solids ► remove the lid and place the cap on the table with the top down so that the cup part of the cap is facing up ► Then, using a VERY clean spatula, take a small amount from the bottle ► gently tap the required amount into a proper container ► Do not return the excess to the original reagent bottle. Dispose of the excess properly. 27

Beaker tansfer ► LIQUIDS BEING POURED FROM A BEAKER ► Use a glass rod as the guide ► Hold the glass rod against the beaker and allow the liquid from the reagent bottle to flow along the glass rod ► See video side ways again 28

Pipette ► There are four types  To Deliver (TD)  To Contain (TC)  To Blowout (TB)  Volumetric ► Each of these comes in all the sizes ► DO NOT allow the tip of the pipette to touch the container or the other solution ► Click on Video 29

Lab report at the end of the instructions First Based on what is shown what is the accuracy Then units Then value at arrow 30

Measure Lab manual 31