Reflection and refraction lab report answers

Reflection And Refraction Lab

Reflection and Refraction

Part 1 - Reflection

DATA TABLE:

Incident angle, θi

30

45

60

Reflected angle, θr

What can you conclude about the relationship of θi and θr? Does this verify the law of reflection?

Part 2 - Reflection:

Step I - Find the image location, circle that point and label it “I”. Measure and record the object distance do and the image distance di. What can you say about the location of the image?

Step J - Is the image real or virtual?

Part 3 - Refraction and the Refractive Index of Water:

Data Table

Experiment

Incident angle, θi

Refracted angle, θr

Index of refraction, n

1

2

3

Average value of the index of refraction, navg = _______________________.

Find the percent difference between the known value and your average experimental value.

Part 4 - Refraction and Refractive Index:

Data Table

Experiment

Incident angle, θi

Refracted angle, θr

Index of refraction, n

1

2

3

Average value of the index of refraction, navg = _______________________.

Find the percent difference between the known value of 1.49 and your average experimental value.

Physics 2

LabPaq: PK-2

A Lab Manual of 11 Experiments for Independent Study

Published by Hands-On Labs, Inc.

Physics 2: Lab Manual of Experiments for the Independent Study of Physics

Designed to accompany Physics LabPaq PK-2 081611

LabPaq® is a registered trademark of Hands-On Labs, Inc. (HOL). The LabPaq referenced in this manual is produced by Hands-On Labs, Inc. which holds and reserves all copyrights on the intellectual properties associated with the LabPaq’s unique design, assembly, and learning experiences. The laboratory manual included with a LabPaq is intended for the sole use by that LabPaq’s original purchaser and may not be reused without a LabPaq or by others without the specific written consent of HOL. No portion of any LabPaq manual’s materials may be reproduced, transmitted or distributed to others in any manner, nor may they be downloaded to any public or privately shared systems or servers without the express written consent of HOL. No changes may be made in any LabPaq materials without the express written consent of HOL. HOL has invested years of research and development into these materials, reserves all rights related to them, and retains the right to impose substantial penalties for any misuse.

Published by: Hands-On Labs, Inc.

3880 S. Windermere St. Englewood, CO 80110 Phone: 303-679-6252 Toll-free: 1-866-206-0773 Fax: 270-738-0979

www.LabPaq.com

E-mail: Info@LabPaq.com

Printed and bound in the United States of America.

ISBN: 978-1-866151-40-6

The experiments in this manual have been and may be conducted in a regular formal laboratory or classroom setting with the user providing their own equipment and supplies. The manual was especially written, however, for the benefit of independent study students who do not have convenient access to such facilities. It allows them to perform physics experiments at home or elsewhere by using LabPaq PK-2, a collection of experimental equipment and supplies specifically packaged by Hands-On Labs, Inc. to accompany this manual.

Use of this manual and authorization to perform any of its experiments are expressly conditioned upon the user reading, understanding, and agreeing to abide by all the safety precautions contained herein. Although the author and publisher have exhaustively researched all sources to ensure the accuracy and completeness of the information contained in this book, we assume no responsibility for errors, inaccuracies, omissions or any other inconsistency herein. Any slight of people, organizations, materials or products is unintentional.

Table of Contents Introduction .................................................................................................................................. 4

Important Information to Help Students Study Science ..................................................... 4 WELCOME TO THE WORLD OF SCIENCE! ................................................................................ 4

Laboratory Equipment and Techniques ........................................................................... 13 Use, Disposal, and Cleaning Instructions for Common Materials ................................... 19

HOW TO WRITE LAB NOTES AND LAB REPORTS .................................................................. 21 Lab Notes .......................................................................................................................... 21 Lab Reports ....................................................................................................................... 23 Laboratory Drawings ......................................................................................................... 27 Visual Presentation of Data .............................................................................................. 28 Computer Graphing Using MS Excel ................................................................................. 32

SAFETY CONCERNS ............................................................................................................... 40 Basic Safety Guidelines .................................................................................................... 41 Material Safety Data Sheets ............................................................................................. 46 Science Lab Safety Reinforcement Agreement ............................................................... 50

EXPERIMENTS 1. Static Electricity or Electrostatics .................................................................................... 53 2. Electric Fields ................................................................................................................... 63 3. Introduction to Electrical Circuits .................................................................................... 74 4. Resistors in Series and Parallel ...................................................................................... 87 5. Semiconductor Temperature Sensor .............................................................................. 96 6. Capacitance in a Circuit ................................................................................................. 102 7. Electric Motor ................................................................................................................. 113 8. Reflection and Refraction .............................................................................................. 119 9. Diffraction Grating ......................................................................................................... 130 10.Polarized Light ............................................................................................................... 141 11.Radioactive Decay ......................................................................................................... 147 APPENDIX Using Statistics .................................................................................................................... 154

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Introduction Important Information to Help Students Study Science

Version 09.3.05

WELCOME TO THE WORLD OF SCIENCE! Don't be afraid to take science courses. When you complete them, you will be very proud of yourself and will wonder why you were ever afraid of the “S” word – Science! After their first science course most students say they thoroughly enjoyed it, learned a lot of useful information relevant to their personal lives and careers, and only regret not having studied science sooner. Science is not some mystery subject comprehended only by eggheads. Science is simply a way of learning about our natural world and how it works by testing ideas and making observations. Learning about the characteristics of the natural world, how those characteristics change, and how those characteristics interact with each other make it easier to understand ourselves and our physical environment and to make the multitude of personal and global decisions that affect our lives and our planet. Plus, science credits on an academic transcript are impressive, and your science knowledge may create some unique job opportunities. All sciences revolve around the study of natural phenomena and require hands-on physical laboratory experiences to permit and encourage personal observations, discovery, creativity, and genuine learning. As increasing numbers of students embrace online and independent study courses, laboratory experiences must remain an integral part of science education. This lab manual’s author and publisher are science educators who welcome electronic technology as an effective tool to expand and enhance instruction. However, technology can neither duplicate nor replace learning experiences afforded to students through traditional hands-on laboratory and field activities. This does not mean that some experiments cannot or should not be replaced or reinforced by computer simulations; but any course of science study must also provide sufficient hands-on laboratory and field experiences to:

Engage students in open-ended, investigative processes by using scientific problem solving.

Provide application of concepts students have seen in their study materials which

reinforce and clarify scientific principles and concepts.

Involve multiple senses in three-dimensional rather than two-dimensional learning experiences that are important for greater retention of concepts and for accommodation of different leaning styles.

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Stimulate students to understand the nature of science including its unpredictability

and complexity.

Provide opportunities to engage in collaborative work and to model scientific attitudes and behavior.

Develop mastery of techniques and skills needed for potential science, engineering, and technology careers.

Ensure advanced placement science courses transfer to college credit.

The knowledge gained from science courses with strong laboratory components enables students to understand in practical and concrete ways their own physical makeup, the functioning of the natural world around them, and contemporary scientific and environmental issues. It is only by maintaining hands-on laboratory experiences in our curricula that the brightest and most promising students will be stimulated to learn scientific concepts and avoid being turned-off by lecture- and textbook-only approaches. Physical experimentation may offer some students their only opportunity to experience a science laboratory environment. All students – as potential voters, parents, teachers, leaders, and informed citizens – will benefit from a well-rounded education that includes science laboratory experiences, when it is time for them to make sound decisions affecting the future of their country and the world. 19th century scientist, Ira Remsen (1846-1927) on the subject of Experimentation:

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This lab manual can be used by all students, regardless of the laboratory facilities available to them. The experiments are based on the principles of micro- and small-scale science which have been successfully used in campus laboratories for decades. LabPaq’s micro- and small-scale experiments can also be performed at home, in a dorm room, or at a small learning center that lacks a formal laboratory. What are Micro- and Small-scale Experiments? You may be among the growing number of students to take a full-credit, laboratory science course through independent study, due to the development and perfection of micro-scale and small-scale experimentation techniques over the past half century. While experimentation on any scale is foundational to fully understanding science concepts, science courses in the past have required experimentation to be performed in the campus laboratory due to the potential hazards inherent in traditional experimentation. Potential hazards, increasing chemical, specimen, and science equipment costs, and environmental concerns made high schools, colleges, and universities reexamine the traditional laboratory methods used to teach science. Scientists began to scale down the quantities of materials and the size of equipment used in experiments and found reaction results remained unchanged. Over time, more and more traditional science experiments were redesigned to be performed on micro and small scales. Educational institutions eventually recognized that the scientific reaction, not the size of the reaction, facilitates learning. Successive comparative assessments have proven that students’ learning is not impaired by studying small-sized reactions. Many assessments even suggest that science learning is enhanced by small-scale experimentation. The primary pioneer and most prominent contributor to micro- and small-scale experimentation was Dr. Hubert Alyea, a chemistry professor at Princeton University, who began utilizing micro-scale experiments in the 1950s. Dr. Alyea reformatted numerous chemistry experiments and also designed many of the techniques and equipment used in micro- and small-scale science today. In the mid-1990s, Dr. Peter Jeschofnig of Colorado Mountain College pioneered the development of LabPaq’s academically aligned, small-scale experiments that can be performed at home. Hands-On Labs, Inc. has subsequently proven that students can actually perform LabPaq's rigorous science experiments at home and still achieve an equivalent, if not higher, level of learning than their campus-based peers.

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The Organization of this Lab Manual Before proceeding with your experiments, please thoroughly read and understand each section of this lab manual, so you understand what is expected of you. Introduction and How to Study Science: These sections include important information about general scientific subject matter and specific information about effectively studying science and conducting science experiments. Read these sections carefully and take them to heart! How to Perform an Experiment and Laboratory Equipment and Techniques: Adhering to the procedures described in these sections will greatly facilitate experimental activities. The laboratory techniques and equipment described primarily apply to full-scale experiments and formal laboratories; however, knowledge of these items is important to a basic understanding of science and is relevant to home-based experimentation. How to Write Lab Notes and Lab Reports: Like all serious scientists, you must record formal notes detailing your activities, observations, and findings for each experiment. These notes will reinforce your learning experiences and science knowledge and provide the basis from which you will prepare Lab Reports for your instructor. This section explains how these documents should be organized and prepared. Safety Concerns: The Basic Safety Guidelines and Safety Reinforcement Agreement are the most important sections of this lab manual and should be reviewed before each experiment. The safety sections are relevant to both laboratory and non-laboratory experimentation. The guidelines describe potential hazards as well as basic safety equipment and safety procedures designed to avoid such hazards. Required Equipment and Supplies: If you are performing these experiments in a non- laboratory setting, you must obtain the LabPaq specifically designed to accompany this lab manual. The LabPaq includes all the basic equipment and supplies needed to complete the experiments, except for minor items usually found in the average home or obtained at local stores. At the beginning of each experiment you will find a materials section listing which items are found in the LabPaq and which items you will need to provide. Review this list carefully before you begin an experiment to ensure you have all required items. Experiments: The experiments included in this lab manual were specifically selected to accompany related course materials for a traditional academic term. These experiments emphasize a hands-on, experimental approach for gaining a sound understanding of scientific principles. The lab manual’s rigorous Lab Report requirements help reinforce and communicate your understanding of each experiment’s related science principles and strengthen your communication skills. This traditional, scientific method approach to learning science reflects the teaching philosophy of the authors, Hands-On Labs, Inc., and science educators around the globe.

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HOW TO STUDY SCIENCE It is unfortunate that many people develop a fear of science somewhere early in life. Yes, the natural sciences are not the easiest subjects to learn; but neither are they the hardest. Like in any other academic endeavor, if you responsibly apply yourself, conscientiously study your course materials, and thoughtfully complete your assignments, you will learn the material. Following are some hints for effectively studying science and any other subject, both on or off campus. Plan to Study: You must schedule a specific time and establish a specific place in which to seriously devote yourself to your studies. Think of studying like you would think of a job. Jobs have specific times and places in which to get the work done, and studying should be no different. Just as television, friends, and other distractions are not permitted on a job, they should not be permitted to interfere with your studies. If you want to do something well, you must be serious about it, and you cannot learn when you are distracted. Only after you have finished your studies should you allow time for distractions. Get in the Right Frame of Mind: Think positively about yourself and what you are doing. Put yourself in a positive frame of mind to enjoy what you are about to learn, and then get to work. Organize any materials and equipment you will need in advance so you don't have to interrupt your work later. Read your syllabus and any other instructions and know exactly what your assignment is and what is expected of you. Mentally review what you have already learned. Write down any questions you have, and then review previous materials to answer those questions. Move on, if you haven't found the answer after a reasonable amount of time and effort. The question will germinate inside your mind, and the answer will probably present itself as you continue your studies. If not, discuss the question later with your instructor. Be Active with the Material: Learning is reinforced by relevant activity. When studying, feel free to talk to yourself, scribble notes, draw pictures, pace out a problem, or tap out a formula. The more physically active things you do with your study materials, the better you will learn. Have highlighters, pencils, and note pads handy. Highlight important data, read it out loud, and make notes. If there is a concept you are having problems with, stand up and pace while you think it through. Try to see the action taking place in your mind. Throughout your day, try to recall things you have recently learned, incorporate them into your conversations, and teach them to friends. These activities will help to imprint the related information in your brain and move you from simple knowledge to true understanding of the subject matter.

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Do the Work and Think about What You Are Doing: Sure, there are times when you might get away with taking a shortcut in your studies, but in doing so you will probably shortchange yourself. The things we really learn are the things we discover ourselves, which is why we don't learn as much from simple lectures, passive videos, or someone simply telling us the answers to our questions. Discovery learning – figuring things out for ourselves – is the most effective and long-lasting form of learning. When you have an assignment, don't just go through the motions. Enjoy your work, think about what you are doing, be curious, ask yourself questions, examine your results, and consider the implications of your findings. These critical thinking techniques will improve and enrich your learning process. When you complete your assignments independently and thoroughly, you will be genuinely knowledgeable and can be very proud of yourself. How to Study Independently There is no denying that learning through any method of independent study is very different from learning through classes held in traditional classrooms. It takes a great deal of personal motivation and discipline to succeed in a course of independent study where there are no instructors or fellow students to give you structure and feedback. These problems are not insurmountable, and meeting the challenges of independent study can provide tremendous personal satisfaction. The key to successful independent study is having a personal study plan and the personal discipline to stick to that plan. Properly Use Your Learning Tools: The basic tools for web courses and other distance learning methods are often similar, consisting of computer software, videos, textbooks, and study guides. Check with your course instructor to make sure you acquire all the materials you will need. You can obtain these items from campus bookstores, libraries, or the Internet. Related course lectures and videos may even be broadcast on your local public and educational television channels. If you choose to do your laboratory experimentation independently, you will need the special equipment and supplies described in this lab manual and contained in its companion LabPaq. For each study session, first work through the appropriate sections of your course materials, because these serve as a substitute for classroom lectures and demonstrations. Take notes as you would in a regular classroom. Actively work with any computer and text materials, carefully review your study guide, and complete all related assignments. If you do not feel confident about the material covered, repeat the previous steps until you do. It is wise to always review your previous work before proceeding to a new section to reinforce what you’ve previously learned and prepare you to better absorb new information. Actual experimenting is among the last things done in a laboratory session.

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Plan to Study: A normal science course with a laboratory component may require you to spend as many as 15 hours a week studying and completing your assignments. To really learn new material requires at least three hours of study time each week for each hour of course credit taken. This applies as equally to independent study as it does to regular classroom courses. On a school campus science students are usually in class for three hours and in the laboratory for two to three hours each week. Then, they still need at least nine hours to read their text and complete their assignments. Knowing approximately how much time is required will help you formulate a study plan at the beginning of the course. Schedule Your Time Wisely: The more often you interact with study materials and call them to mind, the more likely you are to reinforce and retain the information. It is much better to study in several short blocks of time rather than in one long, mind-numbing session. Accordingly, you should schedule several study periods throughout the week or during each day. Please do not try to do all of your study work on the weekends! You will burn yourself out, you won't learn as much, and you will probably end up feeling miserable about yourself and science too. Wise scheduling can prevent such unpleasantness and frustration. Choose the Right Place for Your Home Laboratory: The best place to perform at-home experiments will be determined by the nature of the individual experiments. However, this place is usually an uncluttered room where a door can be closed to keep out children and pets; a window or door can be opened for fresh air ventilation and fume exhaust; there is a source of running water for fire suppression and cleanup; and there is a counter or tabletop work surface. A kitchen usually meets all these requirements. Sometimes the bathroom works too, but it can be cramped and subject to interruptions. Review each experiment before starting any work to help you select the most appropriate work area. Because some of the equipment and supplies in your LabPaq may pose dangers to small children and animals, always keep safety in mind when selecting a work area, and always choose an area where you cannot be disturbed by children or pets. Use a Lab Partner: While the experiments in the LabPaq can be performed independently, it is often fun and useful to have a lab partner to discuss ideas with, help take measurements, and reinforce your learning process. Whether your partner is a parent, spouse, sibling, or friend, you will have to explain what you are doing, and in the process of teaching another, you will better teach yourself. Always review your experiments several days ahead of time so you have time to line up a partner if needed. Perform Internet Research: Students in today’s electronic information age are often unaware of how fortunate they are to have so much information available at the click of a mouse. Consider that researchers of the past had to physically go to libraries, search through card catalogs for possible sources of information, and wait weeks to receive books and journals that may not contain the information they needed. Then they had to begin their search all over again! Now you can find information in a matter of minutes.

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Since most courses today include online components, it is assumed that you have reasonable computer skills. If you make ample use of those skills and include online research as part of your study routine, you can greatly enhance your depth of learning as well as improve your grades. Keep a web browser open as you review your course materials and laboratory assignments. When you encounter words and concepts that you have difficulty fully understanding, perform a quick web search and review as many sites as needed until the definition or concept is clear in your mind. Web searches are especially valuable in science. For example, if you have difficulty with a concept, you can usually perform an image search that will help visually clarify the object of interest. Perform a text search to find descriptions and information from leading scientists at famous institutions all over the world. For unfamiliar terms, enter the word “define” plus the unfamiliar term into your search engine and a myriad of differently phrased definitions will be available to help you. This lab manual lists numerous respected websites that you may find useful, and you will undoubtedly find many more on your own. Rely only on trusted government and educational institutions as sources for valid research data. Be especially skeptical of and double-check information garnered from personal blogs and wiki sites like wikipedia.org, where anyone, regardless of their expertise or integrity, can post and edit information. As students all over the world are finding, the worldwide web is a treasure trove of information, but not all of it is valid! Finally, while website links in this lab manual were valid at the time of printing, many good websites become unavailable or change URLs. If this happens, simply go to one of the other sites listed or perform a web search for more current sites. HOW TO PERFORM AN EXPERIMENT Although each experiment is different, the process of preparing, performing, and recording an experiment is essentially the same. Read the Entire Experiment before You Start: Knowing what you are going to do before you do it will help you organize your work and be more effective and efficient. Review Basic Safety: Before beginning work on any experiment, reread the lab manual’s safety sections, try to foresee any potential hazards, and take appropriate steps to prevent safety problems. Organize Your Work Space, Equipment, and Materials: It is hard to organize your thoughts in a disorganized environment. Assemble all required equipment and supplies before you begin working.

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Outline Your Lab Notes: Outline the information needed for your Lab Notes and set up any required data tables before the experiment, to make it easier to enter observations and results as they occur. LabPaq CDs normally include a Report Assistant containing .rtf files of each experiment’s questions and data tables. These files can be copied and pasted into your Lab Notes to facilitate your compilation of data and text information. Perform the Experiment According to Instructions: Follow all directions precisely in sequential order. This is not the time to be creative. Do not attempt to improvise your own procedures! Think About What You Are Doing: Stop and give yourself time to reflect on what has happened in your experiment. What changes occurred? Why? What do they mean? How do they relate to the real world of science? This step can be the most fun and often creates "light bulb" experiences of understanding. Clean Up: Always clean your laboratory space and laboratory equipment immediately after use. Wipe down all work surfaces that may have been exposed to chemicals or dissection specimens. Blot any unused chemicals with a paper towel or flush them down the sink with generous amounts of water. Wrap dissection specimens in newspaper and plastic and place them in a sealed garbage can. Discard used pipets and other waste in your normal trash. Return cleaned equipment and supplies to their LabPaq box and store the box out of reach of children and pets. Complete Your Work: Complete your Lab Notes, answer the required questions, and prepare your Lab Report. If you have properly followed all the above steps, the conclusion will be easy.

Why Experimental Measurements Are Important:

We measure things to know something about them, to describe objects, and to understand phenomena. Experimental measurement is the cornerstone of the scientific method; thus, no theory or model of nature is tenable unless the results it predicts are measurable and in accordance with the experiment.

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Your primary tasks in a science laboratory course are to create experimentally measured values, compare your results to accepted theoretical or measured values, and gain a full understanding of scientific concepts. This is true for experiments done both inside and outside of a formal laboratory. Each experiment is predicated upon a theory of scientific principle and represents a test of that theory through experimentation, observation, measurements, and analysis.

Laboratory Equipment and Techniques While many of these techniques and equipment are most applicable to specific science disciplines in formal laboratory facilities, knowledge of these items is often required for the study of other science disciplines and when working in a home laboratory. Dispensing Chemicals: To avoid contamination when pouring liquid chemicals from a reagent (ree-ey-juhnt) bottle with a glass stopper, hold the stopper in your fingers while carefully pouring the liquid into the desired container. When pouring from a screw-cap bottle, set the cap down on its top so that it does not become contaminated or contaminate anything. Be certain to put the correct cap on the bottle after use. Never pour excess chemicals back into a reagent bottle, because this may contaminate the reagents. If any liquid spills or drips from the bottle, clean it up immediately. To obtain samples of a powdered or crystalline solid from a container, it is best to pour the approximate amount of solid into a clean, dry beaker or onto a small piece of clean, creased paper for easy transport. Pour powders and crystals by tilting the container, gently shaking and rotating the solids up to the container lip, and allowing the solids to slowly fall out. If you pour too much solid, do not put any solid back in the container. Also, never put wooden splints, spatulas, or paper into a container of solids to avoid contamination. Dropping Chemicals: In micro-scale science, you use only small drops of chemicals, and it is extremely important that the drops are uniform in size and carefully observed. To ensure uniformity of drop size, use scissors to cut off the tip of the pipet perpendicular to the pipet body; cutting at an angle will distort drop sizes. Turn the pipet upside down so the dispensing chamber behind the dropper is full of liquid. Then hold the dropper in front of your eyes so you can carefully observe and count the number of drops dispensed as you slowly squeeze the pipet.

You can see the incorrect (left) and correct (right) way to dispense drops. The pipet should be held in a vertical position at eye level to ensure drops are uniform in size and the correct drops are dispensed.

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Heating Chemicals: Heat solid and liquid chemicals with great care to prevent explosions and accidents.

Liquids in Beakers: To heat liquids in beakers or flasks, ensure that these containers are well supported above the heat source. Generally, the beaker or flask is placed on wire gauze supported by an iron support attached to a stand. The heat source is placed under the beaker or flask. Liquids in Test Tubes: When heating liquids in test tubes, always use a test tube holder. Evenly heat the test tube contents by carefully moving the test tube back and forth in the flame. Heat the test tube near the top of the liquid first; heating the test tube from the bottom may cause the liquid to boil and eject from the tube.

Heating Sources for Small-scale Techniques: For micro- and small-scale science experimentation, the most commonly used heat sources are alcohol burners, candles, and burner fuel. Alcohol burners can be a problem because their flame is almost invisible, and they cannot be refilled while hot. Candles, while effective for heating small quantities of materials, tend to leave a sooty, carbon residue on the heated container that obstructs observations. Sterno and similar alcohol based fuels are very volatile and cannot be safely shipped; however, the Glycol-based fuel used in LabPaqs is safe to ship. Chafing dish (i.e., burner fuel) is actually the best of these alternatives because it has a visible flame, is easily extinguished, and does not leave excessive flame residue. Regardless of the type of burner used, never leave an ignited heat source unattended. Mass Measurement Equipment: Note that weighing scales are often called balances since weights are calculated using balance beams. Triple and quadruple beam balances are the most common measuring equipment found in laboratories. However, with today's precision technology, digital top-loading balances are becoming increasingly popular.

Triple and Quadruple Beam Scale: These balances typically include a hanging pan and vary in their degree of accuracy. After the scale has been set at zero, the object to be weighed is placed in the hanging pan, and balancing weights are added or subtracted by moving a pointer across a horizontal bar scale. When exact scale is achieved, the pointer indicates the object’s mass. Digital Top Loading Balance: This scale is initially zeroed by pressing the zero button. If your are using weighing paper or a small beaker, first tare the paper or beaker by placing it on the scale and pressing the tare button. This will produce a zero reading, and the weight of the paper or beaker will be excluded from the weighing process. Hanging Spring Scales: Measurements are taken by suspending the item from a scale, often within a container. Spring scales are not easily tared, so the container weight should be separately calculated and subtracted from the combined weight of the item and the container.

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The Non-digital Analytical Balance: This instrument is very delicate, and the instructions for its use are quite detailed. Because of its extreme sensitivity, weighing on the analytical scale must be carried out in a closed chamber that is free from drafts. This instrument is seldom used by first-year science students.

Volume Measurement Equipment: To obtain accurate measurements from any glass volume measurement container, such as a beaker or graduated cylinder, you must identify and correctly read a curved surface known as the meniscus. The meniscus of water and water- based solutions concaves downward and is read at the very bottom of its curve. A mercury meniscus is convex and is read at the very top of its curve. There is no meniscus issue associated with plastic containers. Filtration Equipment: Gravity filtration is used to remove solid precipitates or suspended solids from a mixture. It works like a small funnel or spaghetti strainer, except that it is lined with fine, conical filter paper to trap the solids. After pouring a mixture into the filter from a beaker, use a special spatula, called a rubber policeman, to scrape any remaining solids from the beaker wall into the conical filter paper. Then, use a wash bottle to rinse residue from both the beaker and rubber policeman into the filter cone to ensure that all the mixture's particles pass through the filter. Suction filtration uses a vacuum to suck a mixture through a filter. It is much faster than but not always as efficient as gravity filtration. The required vacuum is usually created by the aspirator of a laboratory water faucet. Bunsen Burner: This old, tried-and-true heat source relies on the combustion of natural or bottled gas. To achieve the best flame, you must properly adjust the burner's gas inlet valve and air vent. Open the valves only halfway before lighting the burner. The safest way to light the burner is to bring a lighted match to the flame opening from the side, not the top. When the burner is lit, close the air vent and adjust the gas inlet valve until the flame is approximately 10 cm high. The flame should be luminous and yellow. Next, open the air vent until the flame becomes two concentric cones. The outer cone will be faintly colored and the inner cone will be blue. The hottest part of the flame is at the tip of the blue cone. Graduated Cylinder: Graduated cylinders are available in a wide range of sizes. To read a volume in a graduated cylinder, hold the cylinder at eye level so the contents level and you can directly view the meniscus. Looking at a meniscus from below or above will create parallax and cause a false reading. Always read any scale to the maximum degree possible, including an estimate of the last digit. Buret: Burets are long, graduated tubes usually used in titration. They have a stopcock or valve on the bottom that allows you to dispense liquids in individual drops and accurately measure the quantity dispensed. Use caution when opening the stopcock to ensure that only one drop is dispensed at a time. Pipet: Pipets are small tube-type containers with openings at one end if made of plastic or at both ends if made of glass. They come in a range of volumes and are generally used to transfer specific amounts of liquids from one container to another.

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Berel Pipet: These soft and flexible pipets are made of polyethylene plastic and are extensively used in LabPaqs. They have long, narrow tips and are used to deliver chemicals and to collect products. Berel pipets come in different sizes, and their tips can have different diameters and lengths. You can modify them to serve diverse purposes such as chemical scoops, gas generators, or reaction vessels. Volumetric Flask: Volumetric flasks are pear-shaped flasks with long necks used for the preparation of solutions whose concentrations need to be very accurate. Flasks come in a variety of sizes ranging from a few milliliters to several liters, and their volume levels are precisely marked. When the liquid level inside a volumetric flask is such that the meniscus lines up with the calibration mark on the neck, the volume of the liquid is exactly as stated. Unlike volumetric flasks, the markings on beakers, Erlenmeyer flasks, and most other laboratory containers are very good approximates but are not intended to be exact and precise volume measurements. Wash Bottles: These plastic squeeze bottles produce a small stream of water that can be easily dispensed as needed (e.g., washing out residue from a container). The bottles usually contain distilled or deionized water and are typically used to top off the last few milliliters of a vessel and avoid overfilling. In micro- and small-scale experimentation, plastic pipets are used for similar functions. Tissue Culture Well Plates: These microplates are plastic trays containing numerous shallow wells arranged in lettered rows and numbered columns. Similar to test tubes and beakers, you can use the wells to observe reactions, to temporarily store chemicals during experiments, and to hold pipets. The most commonly used plates are 24-well and 96-well. Distilled Water and Deionized Water: Tap water frequently contains ions that may interfere with the substances you are studying. To avoid such interference, use distilled or deionized water any time water is needed for dilution of concentration or the preparation of experimental solutions. Wash used glassware with soap, rinse with tap water, and rinse again with distilled water.

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© Hands-On Labs, Inc. LabPaq PK-2 19

Use, Disposal, and Cleaning Instructions for Common Materials These procedures are not repeated for each experiment, because it is assumed students will always refer to them before beginning any experiment. Properly cleaning the laboratory after experimentation is a safety measure! Instrument Use

Small quantities of chemicals are usually packaged in thin stem pipets. The drop size dispensed from small dropper bottles is different from that of the pipets. Most experiments require pipet-sized drops. It may be necessary to squeeze a few drops of chemical from a dropper bottle into a well plate, and then use a clean, empty pipet to suck up and drop the chemical.

Once dispensed, do not return chemicals to their dropper bottles as this could cause

contamination. To avoid over-dispensing, squeeze out only a few drops of chemicals into a well plate at a time. Squeeze out more as needed.

To use burner fuel, unscrew the cap, light the wick, and place the can under a burner

stand. Extinguish the fuel by gently placing the cap over the flame to deprive it of oxygen. Leave the cap sitting loosely on top of the wick when you are not using the fuel in order to avoid unnecessary evaporation and ensure an ample supply of fuel for all experiments. Allow the fuel to cool completely before tightly screwing on the cap for storage. If you screw the cap on while the fuel is still hot, you may create a vacuum that will make it very difficult to reopen the fuel can in the future.