Science Lab Equipment

You should know the name of each piece and its basic use.

For exact volume measurements of liquids. Pipet on the left is a Volumetric pipet. It has only one graduation for delivering one exact volume. Pipet on the right is a Mohr pipet. It has graduations for delivering any number of exact volumes.

    Pipet There are several styles of fillers used to draw liquids into a pipet. HHS chemistry students use a standard pipet bulb, described in lab techniques below.

Never draw a liquid into a pipet with your mouth.

      Pipet filler

Used in conjunction with a vacuum connection to a water faucet to speed up filtration.

Filter flask The Erlenmeyer flask is the most common flask in the HHS chemistry lab. It is used to contain reaction solutions.

Erlenmeyer flask

The rounded bottom of the florence flask makes it ideal for boiling liquids. It also makes this flask easy to tip over when sitting on the lab table.

Florence flask The volumetric flask is used to make solutions. It has a precise graduation line in the neck of the flask. A solute is placed into the flask, then the solvent is used to bring the total

Volumetric flask

volume up to the graduation.

Beakers are the most versatile glassware in the lab and can be used for just about anything. The volume graduations on beakers should be used only for "ballpark" estimates.

    Beaker

Used to make accurate measurements of liquid volumes. The bumper ring on larger cylinders is to prevent breakage if tipped over. Keep it near the top.

Graduated cylinder

This dish is used to recover dissolved solids by evaporation. While it can be heated, it should not be used for "strong" heating.

Evaporating dish

A watch glass can be used like an evaporating dish for very small amounts of liquid. It can also be used to cover beakers.

    Watch glass

When attached to the ring stand, this iron ring is used to support glassware above the lab table.

    Support ring

When attached to the ring stand, this clamp is used to hold a large test tube or Florance flask above the lab table.

    Utility clamp

Crucibles are used as a container when something requires "strong" heating.

Crucible and cover These tongs are used for picking up crucibles and crucible covers only.

        Crucible tongs

Used as a support for beakers when

    Wire gauze Used to light a lab burner. Not a toy

        Striker

placed across a support ring.

noisemaker during lab.

Used to grind solids into powers.

Mortar and Pestle

Used to hold test tubes for short periods of "gentle" heating.

Test tube holder

When lined with filter paper, used to filter suspended solids from a liquid.

Filter funnel Used for rinsing solids out of a container when filtering.

Wash bottle

Used to transfer solids from their original container to a scale for weighing.

Chemical spoon Used to close hoses by pinching them together.

Hose clamps

Dessicators are used to provide a dry environment for a crucible or substance to cool down. This is critical in quantitative work where moisture can affect mass results. A common dessicant is anhydrous calcium chloride. Colored indicator crystals are usually included to tell the user the condition of the dessicant. A gray color in the crystals usually indicates that the dessicant is dry and will absorb moisture. A pink color usually means that the dessicant is "hydrated". When this happens, the water can be removed by heating it in an oven.

Desiccator

Science Lab Techniques

measuring with a graduated cylindar measuring with a pipet measuring with an electronic balance

using filter paper and funnel using litmus paper using a magnetic stirrer

measuring with a triple-beam balance

using a laboratory burner using a calorimeter

titration

using a hotwater bath using a fume hood generating and

collecting gases

distillation

Measuring the volume of a liquid with a graduated cylindar:

The surface of a liquid confined in a cylindar curves to form what is known as a meniscus. The meniscus of most liquids curves up the sides of the container, making the center of the curve appear lower than the edges. Mercury is one of very few exceptions -

it curves down at the edges. Since reading the meniscus at the top or at the bottom of the curve will make a difference in the volume measured, it is generally agreed to always read the bottom of the curve. The smaller the container, the greater the curve of the meniscus. Pictured below is the meniscus in a 10 ml graduated cylindar. To gain experience in reading liquid volumes, click on the picture to enlarge it and read the volume in the following way:

1. The largest graduations on this graduated cylindar are numbered, representing milliliters. What whole number of milliliters are represented in the picture? answer

2. There are five graduations from one major line to the next in this picture. In other words, each milliliter is divided into tenths and each small graduation represents two tenths. What volume is represented in the picture, to the nearest tenth of a milliliter? answer

3. Both whole milliliters and tenths of milliliters can be read from the graduations in the picture. If divisions between the tenths graduations are estimated, the volume can be read to hundredths of a milliliter. What is the volume of liquid in the picture to the nearest hundredth of a milliliter? answer

As the diameter of the cylindar increases, the curve of the meniscus flattens out. See a

picture of the meniscus in a 100 ml graduated cylindar. While the curve is not as pronounced, because of its thickness, we must still read the bottom of the meniscus. What volume of liquid is represented in the picture, to three significant digits? answer

You can see that the lines drawn on the answer pictures help identify the location of the bottom of the meniscus. If reading volumes in a cylindar is going to be regularly done,

making a buret card might be worthwhile. This is a small index card with a very thick horizontal line drawn on it with a magic marker. By holding the card behind the cylindar, and immediately below the bottom of the meniscus, the volume can be easily read.

Measuring the volume of a liquid with a pipet:

Pipets are much more accurate than graduated cylindars. Reading the volume of liquid in a pipet is just like reading a graduated cylindar, however there is one additional technique

needed with a pipet. The diameter does not allow a liquid to be poured into a pipet - the liquid must be drawn into the pipet. This picture shows two of several types of pipet bulbs used to draw a liquid into a pipet. The red bulb is known as a standard pipet bulb. The black bulb is known as a safety pipet bulb. Much of the "professional" lab work today is done with automatic pipets. These are expensive little gadgets that come in many different volumes, each delivering exactly its assigned volume with one click of a button. High school chemistry students need to know the basic

techniques of pipetting, so you will be using glass pipets and the standard pipet bulb.

The standard pipet bulb requires manual dexterity that is improved by repetitive use. You may have to practice using the bulb with a pipet before you are able to accurately transfer a measured volume of liquid. The technique goes something like this:

Pour slightly more liquid than needed into a beaker using the "ballpark" graduations on the beaker. Never pipet directly from a reagent bottle.

Place the tip of the pipet below the surface of the liquid in the beaker. Squeeze the pipet bulb and press it firmly over the top of the pipet. Do not force

the bulb onto the pipet. The soft plastic collar of the bulb is tapered inside to insure a good seal as long as you keep a steady pressure between the pipet and the bulb.

Gradually release the presure of your squeeze on the bulb and allow the liquid to be drawn into the pipet. Draw more liquid than needed, but do not allow the liquid to enter the bulb.

With the tip of the pipet still below the liquid's surface, quickly remove the bulb and place your finger or thumb over the top of the pipet to prevent the solution from draining back into the container.

Record the exact volume of liquid in the pipet (remember the meniscus). (Note: this is the step that requires the most practice). To release the liquid, slowly

roll your finger to the side just enough to break the seal over the top of the pipet and allow the liquid to flow. To stop the flow of liquid, roll your finger back.

Measuring mass with an electronic balance:

The electronic balance has many advantages over other types of balance. The most obvious is the ease with which a measurement is obtained. All that is needed is to place

an object on the balance pan and the measurement can be read on the display to hundredths of a gram. A second advantage, using the Zero button on the front of the balance, is less recognized by beginning science students. Because one must never place a chemical

directly on the balance pan, some container must be used. Place the container on the balance and the mass of the container will be displayed. By pressing the Zero button at this point, the balance will reset to zero and ignore the mass of the container. You may now place the substance to be weighed into the container and the balance will show only the mass of the substance. This saves calculation time and effort. However, when the container is removed from the balance, the display will go into negative numbers until the Zero button is pressed again.

Our electronic balances also have a Unit button on the front. Pressing this button will change the units being measured. Since we have very few times when we need something other than metric units, you should not have to change the mode on the balance. Because of the Unit and Zero buttons, there are two things you must always do before placing objects onto an electric balance to be measured:

1. See that the display is reading 0.00 2. See that the unit sign in the upper right of the display shows g

When finished with the electronic balance, press the On/Off button and hold it down until the display shows OFF.

Measuring mass with a triple-beam balance:

The triple-beam balance was once the "standard" balance in the general chemistry lab. While the electronic balance has replaced it in many cases, good science students should be familiar with the triple-beam balance and how to read one. The balance is named for its three "beams". An object is placed on the pan of the balance and

tares on the beams are moved to balance the mass. As you face the balance, the back beam is graduated in 10 gram steps and the middle beam is graduated in 100 gram steps. It is very important that the tares on these two beams are in the notch for the whole number of grams and not in between notches. The front beam is a sliding scale graduated in grams. The tare on this beam can be positioned anywhere on the scale. Masses on a triple-beam balance can be read to tenths of a gram, and estimated to hundredths. Clicking on the balance picture will give you a close view of the position of the tares on the three beams. What mass is represented, to five significant digits? answer

Using a laboratory burner:

Many chemistry experiments require something to be heated. This is done with one of several types of laboratory burners. The lab burners at Howe High School use propane gas delivered through the gas outlets at student lab stations. Before attempting to light any lab burner, check to see that the jet hole between the base and the burner tube is free of obstruction. If chemicals have covered this jet, the burner will not operate properly.

After attaching the hose to the gas outlet, turn the handle on the outlet parallel to the nozzle to open the gas valve. The gas valve is turned off by turning the handle 90 degrees in either direction. Carefully check to see that you hear gas escaping from the mouth of the burner tube. When you are

sure that you have gas, bring the head of the striker over the burner and squeeze the striker handle. The spark produced will ignite the gas and your burner is lit. Adjust the air control vent so that the flame has the proper color pictured here. A yellow flame is an indication of a lack of oxygen, meaning that the air vent needs to be opened. The hottest part of the burner flame is just at the top of the bright blue inner cone. Normal heating is done with an object at the top of the light blue outer cone, while strong heating is done with an object at the top of the bright blue inner cone. To heat a container gently, move the container back and forth through the outer cone.

Filtering a precipitate from a solution:

Filtering a solid out of a liquid is done using filter paper and a filter funnel. The filter funnel is supported by the ring on a ring stand. Lay a clay triangle across the ring, then place the filter funnel into the triangle.

To prepare the filter paper, fold the paper in half , then fold it in half again.When you look at the open edge of the folded paper you will see four edges of paper. With thumb and finger, catch three of these edges. Squeeze the sides of the folded paper and a cone will form with three thicknesses of paper on one side and one thickness of paper on the other. Place this cone of paper into the filter funnel. Place a "catch container" under the stem of the filter funnel and adjust the height of the ring on the ring stand until the tip of the stem is below the mouth of the container.

Use a wash bottle and wet down the inside of the filter paper. This will help it stick to the funnel. You are now ready to filter. Carefully pour the liquid to be filtered into the mouth of the funnel. Do not let the liquid rise to the top of the filter paper. If any liquid goes over and around the paper, your procedure is ruined. Be patient, it will take time for the liquid to move through the pores of the paper. When all the original liquid has been poured into the funnel, use the wash bottle to rinse any remaining precipitate out of the original container. Do not touch or try to stir the liquid inside the filter paper. The wet paper is easily torn, which will ruin your procedure.

If the objective of your filtration is the solid-free liquid, throw the filter paper and its contents into the trash. If your objective is the solid, carefully remove the filter paper and set it in a secure place to dry.

Titration is a neutralization reaction between acid and base:

The classic lab apparatus for a titration uses a set of double burets - pictured here. One buret holds the acid, the other the base. The common procedure is to place a measured volume of the acid into a flask, then add two drops of phenolphthalein indicator. This indicator is colorless in an acid, but turns dark pink in a base. Small amounts of the base are added to the flask as it is being slowly twirled to mix the solution. At the end-point, or "neutralization", the phenolphthalein will be barely pink when viewed over a white background. For more about titration, go to this webpage.

Using litmus paper to determine acid or base:

An acid turns blue litmus paper red and a base turns red litmus paper blue. While even grade-school students know this, there is one mistake commonly made when using either litmus or pH paper strips. You should never dip the test paper into the solution being tested. While the degree to which this contaminates the solution is not great, good chemistry students know not to do it. Always use a glass stirring rod. Dip a clean stirring rod into the solution, then touch the wet stirring rod to the paper.

Using a magnetic stirrer:

A magnetic stirrer is helpful for dissolving solids in liquids. While there are several different styles, all will at least have a base with a speed-controlled spinning magnet inside and an external stirring bar. The stirring bar is placed into a flask or beaker by gently sliding it along the wall of the container. To prevent breakage, do not drop the bar onto the bottom of the container. Place the container on the stirrer base and turn the speed control knob to its lowest setting. Use just enough speed to start the bar turning in the container. The picture here shows the "vortex" that forms inside the continer. Be patient, the bar might "hop" at excess speeds, causing splashing.

If using exact volumes, as with a volumetric flask, be sure take the measurements before adding the stirring bar.

When stirring is completed, keep the stirring bar in the container by "decanting" the liquid into another container. Be sure to carefully wash the original container and the stirring bar.

Distillation:

In general chemistry, distillation can be used to remove dissolved substances from a liquid or to separate a mixture of liquids that have different boiling points.

To successful separate a mixture of liquids, you must know the boiling point of each liquid involved and be able to measure temperature changes as heat is applied. Heat is added to the mixture until it reaches the first boiling point. The temperature must be

kept at this temperature until all the first liquid is removed. The temperature is then allowed to rise to the next boiling point and the second liquid removed. The closer these boiling points are together, the more difficult it is collect pure liquids from the mixture.

One distillation apparatus is pictured at right. The picture here shows an apparatus available in this class. No matter how the apparatus is set up, the following things must be accomplished:

The original liquid is heated. The temperature is measured. The vapor is collected and condensed back into a

liquid. The new liquid is collected.

Generating and collecting gases:

A gas generating bottle is used to produce gases from a chemical reaction. The solid is placed into the bottle, then a solution is poured down the funnel. As the gas builds, it will move into the collecting tube at the top of the bottle. The picture here shows the collection of a gas that is heavier than air. This is indicated by the gas going "down" into the upright collecting container. If the gas were lighter than air, it would not go down into the container. Gases that are lighter than air must be collected by water displacement.

For water displacement, the container is filled with water then inverted into a water trough. The gas is bubbled up under the container and pushes the water out. This is a very common procedure in general chemistry labs and has only one draw-back. If the gas being generated is highly soluble in water, precise measurements of the gas produced will not be possible.

Fume Hood:

The fume hood is a safety glass-front cabinet with an exhaust fan. It is used for experiments known to produce noxious fumes or smoke. Do the following to perform an experiment in the hood:

1. Raise the door of the hood 2. Turn on the light and set up the apparatus 3. When all material for the experiment is ready, turn on the fan 4. Pull the hood door at least 1/3 way down 5. Perform the experiment 6. When finished, pull the door all the way down until all smoke and fumes are

removed 7. Turn off the fan and light, then remove the equipment to a regular lab station for

cleaning 8. Leave the hood clean

Hotwater Bath:

A hotwater bath is used in the general chemistry lab to heat something slowly and evenly. Many different types of glassware can be used to set up a hotwater bath. What glassware you use will depend on the quantity of the substance you wish to heat. All hotwater baths put the substance to be heated in a container then place that container into a container of water. Heat is then applied to the water container. The substance is heated by the water, not the burner flame.

In addition to heating slowly and evenly, water baths are also safer than direct heat. For this reason, highly volatile substances should only be heated using hotwater baths.

Calorimeter:  (chem lab 205)

The specific heats of metals can be determined by calorimetry. Calorimetry involves heating the metal to a known temperature, placing it into a measured amount of cold water in an insulated container called a calorimeter and measuring the resultant rise in temperature of the water in the calorimeter. The temperature of the water in the calorimeter will rise rapidly as heat is transferred from the hot metal to the cold water. After the water reaches a maximum temperature, it will slowly decrease.

While there are very expensive calorimeters that will absorb no heat from the reaction inside, the heat absorbed by the "coffee-cup" calorimeter shown here is negligible within the range of our measuring instruments.

An equation used in calorimetry calculations:

Light Microscopes

A microscope is an instrument that produces an enlarged image of an object. Biologists use microscopes to study things that are too small to be seen with the unaided

eye. Most microscopes are called light microscopes because they accomplish their task by using lenses to bend light rays.

Read about the contribution of Antonie van Leeuwenhoek. and Robert Hooke

  (bio lab 025) Observing an object:

Because the light rays from an object cross before reaching your eye, the image you see through most microscopes will be inverted and upside down.

Magnification: the increase of an object's apparent size.

Resolution: the power to show details clearly. Resolution allows the viewer to see two objects that are very close together as two objects rather than as one.

Compound microscopes use multiple lenses to produce an increase in magnification. If the eyepiece lens enlarges by a factor of 10 (10X) and the objective lens enlarges by a factor of 40 (40X), the total magnification is the product of the two - 400X. Resolution is controlled by the quality of the lenses being used - the better the lenses, the better the resoultion.

Basic parts of a compound light microscope:

Eyepiece (Ocular): Usually contains a 10X lens. Arm: contains the housing for the fine and coarse adjustments and connects the

base of the microscope to the nosepiece and ocular. Nosepiece: A rotating head that has the objective lenses attached to it. The lens to

be used should "click" into position when the wheel is gently turned so that it is directly over the speciman slide.

Objective: Basically a housing for a lens. Our microscopes have three objective lenses - 4X, 10X, and 40X.

Stage: The speciman slides rests on this part of the microscope. Coarse adjustment knobs: The larger of two sets of knobs located on either side

of the arm, just above the base. This adjustment is used to make large adjustments in focusing by moving the lenses up and down. Never use this adjustment when using the 40X objective.

Fine adjustment knobs: The smaller of two sets of knobs located on either side of the arm. This adjustment is used to make small adjustments in focusing. It has a limited amount of movement and is most efficiently used after focusing with the 4X objective and coarse focus, then increasing magnification and making final adjustments with the fine focus knob.

Light source: Located directly under the stage. Adjustable diaphragm: This rotating wheel on the underside of the stage allows

the user to adjust the amount of light that passes through the specimen. As a general rule, the lowest intensity of light that allows you to resolve the structure of the object you are viewing should be used.

Care and handling of the microscope:

A microscope is a delicate piece of equipment and should be treated with care. Use two hands when carrying the microscope. Place one hand around the arm of

the microscope and the other under the base for support. Carry the microscope upright and close to the body. Place the microscope flat on the table, but not too near the edge where it might

be knocked off. If it becomes necessary to clean the lenses on the microscope, ask your facilitator

for a piece of lens paper. Other materials, such as paper towel, can scratch the surface of the lens.

  (bio lab 034) Viewing specimens with a microscope:

In most instances, light must pass through any object to be viewed with a light microscope. For this reason, an object to be viewed must be fairly thin. Thick objects may be sliced into thin sections for viewing.

Many objects do not have distinct, contrasting colors. This makes seeing details

difficult. Observation may be improved by staining with a biological stain.

Natural cheek cells.

Stained cheek cells. Making a wet-mount slide:

Place a clean slide on the lab table. Handle slides at the ends, not the center, to avoid getting fingerprints in the viewing area of the slide.

Add specimen to the slide. For liquid samples, place one small drop in the center of the slide. For solid samples, place the sample in the center of the slide and

add one drop of water or stain. Hold the coverslip by the edges to avoid fingerprints. Set one edge against

the slide and lower it until it contacts the liquid. The liquid should spread across the whole area of the coverslip.

Never view a slide without a coverslip. The coverslip protects the objective lens from the liquid on the slide.

Observing protozoans and crustaceans: Small animals are often difficult to observe because of their motion. They

must be slowed if any but the lowest magnification is to be used. Several things can be done to help in this reguard.

Methyl cellulose 1.5% - a viscous material that can be mixed with the water of a wet mount to slow the animals without harming them. Use a toothpick to mix the two on the slide before adding a coverslip.

Cotton fibers - the natural cotton fibers will provide barriers to block some of the movement of the animals. Using a very small

piece of natural cotton, pull the fibers apart. Lay the cotton in the center of the slide before adding the water of the coverslip.

Well slides - microscope slides that have a depression in the center of the slide. This depression may hold a small drop of water, keeping it from spreading like on a flat slide. The disadvantage is that the animals now have more room to move up and down, instead of from side to side.

Cleanup: Unless otherwise instructed, wipe the sample and coverslip off the slide

with a paper towel when finished. Throw the paper towel and its contents away. Return the microscope slide to its container.

 

Electron Microscopes

Light microscopes are limited to about 2000X by the properties of light. Another type of microscope called an electron microscope uses a beam of electrons instead of light and magnets instead of lenses. Because of the high-energy particles involved, these microscopes cannot be used to view living specimens.

There are two types of electron microscopes:

Transmission electron microscope - TEM: transmits a beam of electrons through a very thinly sliced specimen. TEMs can magnify objects up to 1,000,000 times.

Scanning electron microscope - SEM: specimens are not sliced. The surface of the specimen is sprayed with a fine metal coating and a beam of electrons is passed over the specimen. Electrons from the metal coating are projected onto a screen or photographic plate. SEMs can magnify objects up to 300,000 times.

Go to this website to use a virtual scanning electron microscope. 

 

Lab Station Equipment

ring stand ring stand clamp support ring utility clamp test tube holder bunsen burner burner hose striker crucible tongs wire gauze

test tube brush

beaker brush clay triangle watch glass 400ml beaker 250ml beaker 250 erlenmeyer flask stirring rod test tube 10ml graduated cylinder 100ml graduated cylinder

filter funnel

An electronic balance and a triple-beam balance are always available.

If you request additional equipment for a particular experiment, that equipment should be returned to your science facilitator when you have finished with it - do not leave it at your lab station.

 

 

Lab-tray Equipment

Some experiments may be done on a "lab tray", without running water and burners. Lab-tray experiments are similar to regular lab experiments, except that they are done on a "micro" scale - using very small amounts of chemicals. These experiments are done at your student table, instead of at a lab station and usually don't require PPE. Some of this equipment is disposable and some is reusable - if you are in doubt, ask! All clean-up must be done with paper towels.

Equipment available for a lab-tray experiment includes:

plastic lab tray plastic micro-bottles and stand - to replace reagent bottles. plastic well-plates - to replace test tubes and beakers. single-serving plastic pop bottles - for standard solution

preparation. wood splints - for just about anything. paper cups baggies straws balloons

paper towels - for clean-up.