chemistry worksheet #1

Pathways to Chemistry

Chemistry for college, middle and high school, homeschooled students, teachers and parents.

General Chemistry 1 Worksheets

Please click on a worksheet. An Answer Key link can be found on the worksheet page.

Matter and Measurement in Chemistry

Atoms, Ions, and Moles

Chemical Reactions and Mass

Reactions in Aqueous Solution

Thermochemistry

Electronic Structure of Atoms

Periodic Trends and Ionic Compounds

Covalent Bonds and Lewis Dot Structures

Bonding Models for Covalent Compounds

Gases: Properties and Behavior

Printable Chemistry Worksheets

Free pdf Worksheets to Download or Print

• Chemical Laws
• Periodic Table
• Projects & Experiments
• Scientific Method
• Biochemistry
• Physical Chemistry
• Medical Chemistry
• Chemistry In Everyday Life
• Famous Chemists
• Activities for Kids
• Abbreviations & Acronyms
• Weather & Climate
• Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
• B.A., Physics and Mathematics, Hastings College

This is a collection of chemistry worksheets in pdf format. The answers to the questions are available on separate worksheets so you can fill them out and then check your work. Please feel free to download these to your computer, print them, and use them as hand-outs.

• Metals, Nonmetals, and Metalloids Worksheet
• Metric to English Conversions Worksheet
• Metric to English Conversions Answers
• Metric to Metric Conversions Worksheet
• Metric to Metric Conversions Answers
• Temperature Conversions Worksheet
• Temperature Conversions Answers
• Temperature Conversions Worksheet #2
• Temperature Conversions Answers #2
• Moles to Grams Conversions Worksheet
• Moles to Grams Conversions Answers
• Formula or Molar Mass Worksheet
• Formula or Molar Mass Worksheet Answers
• Practicing Balancing Chemical Equations - Worksheet
• Balancing Chemical Equations - Answers
• Practicing Balancing Chemical Equations - Worksheet #2
• Balancing Chemical Equations - Answers #2
• Practicing Balancing Chemical Equations - Worksheet #3
• Balancing Chemical Equations - Answers #3
• Balancing Equations - Worksheet #4
• Balancing Equations - Answer Key #4
• Common Acid Names & Formulas - Worksheet
• Acid Names and Formulas - Answers
• Practice Calculations with Moles - Worksheet
• Mole Calculations - Answers
• Acid & Base pH - Worksheet
• Acid & Base pH - Answers
• Gas Laws Answers
• Gas Laws Answers - Shown Work
• Limiting Reagent - Worksheet
• Limiting Reagent - Answers
• Calculating Molarity - Worksheet
• Calculating Molarity - Answers
• Balancing Redox Reactions - Worksheet
• Balancing Redox Reactions - Answers
• Printable Element Crossword
• Printable Element Crossword - Answers
• Chemical Names to Chemical Formulas - Worksheet
• Chemical Names to Chemical Formulas - Answer Key
• Chemical Formulas to Chemical Names - Worksheet
• Chemical Formulas to Chemical Names - Answer Key
• Chemistry Element Word Search

Printable Periodic Tables

Here are some printable periodic tables to help you out, also in pdf format.

• Color Printable Periodic Table - Pretty much everything you need that can fit on a page and still be readable. Color table with atomic numbers, element symbols, element names, atomic weights, periods, and groups. [ 2013 Edition ] [ 2012 Edition ]
• Black/white Printable Periodic Table - Black/white table with atomic numbers, element symbols, element names, atomic weights, periods. [ 2013 Edition ] [ 2012 Edition ]
• Blank Printable Periodic Table - Fill in the boxes yourself.
• Electron Configuration Periodic Table - Periodic table that lists the electron configurations for each element.
• Color Printable Periodic Table - Color table with atomic numbers, element symbols, atomic weights, periods, and groups. (no names)
• Basic Printable Periodic Table - Black/white table with atomic numbers, element symbols, atomic weights, periods. (no names)
• Basic Periodic Table with Element Names - Black/white table with element symbols, names, atomic numbers, and periods. (no weights)
• Basic Periodic Table with Element Names (color) - Color periodic table with element symbols, names, atomic numbers, periods, and groups. (no weights)

The atomic weights given on these tables are the most recent (2007) values as accepted by the IUPAC.

Printable Scientific Method Flow Chart

This is a flow chart of the steps of the scientific method, available as a PDF file:

• Scientific Method PDF

Also available is a PDF of a pie chart of the elemental composition of the human body .

• Printable Periodic Tables (PDF)
• Printable Periodic Table of the Elements With Oxidation States
• A List of Common General Chemistry Problems
• How to Use a Periodic Table of Elements
• Chemical Element Charges Table
• How to Balance Equations - Printable Worksheets
• Basic Printable Periodic Table of the Elements
• Printable Color Periodic Table of the Elements
• Chemistry 101 - Introduction & Index of Topics
• Printable Periodic Tables - 2015 Edition
• 20 Practice Chemistry Tests
• Printable Chemistry Worksheets - Chemical Names and Formulas
• Periodic Table of the Elements - Oxidation Numbers
• Overview of High School Chemistry Topics
• Color Periodic Table of the Elements - Valence Charge
• Here's How to Download the Periodic Table With Electron Configurations

If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

To log in and use all the features of Khan Academy, please enable JavaScript in your browser.

Chemistry library

Welcome to the chemistry library, unit 1: atoms, compounds, and ions, unit 2: mass spectrometry, unit 3: chemical reactions and stoichiometry, unit 4: more about chemical reactions, unit 5: electronic structure of atoms, unit 6: periodic table, unit 7: chemical bonds, unit 8: gases and kinetic molecular theory, unit 9: states of matter and intermolecular forces, unit 10: chemical equilibrium, unit 11: acids and bases, unit 12: buffers, titrations, and solubility equilibria, unit 13: thermodynamics, unit 14: redox reactions and electrochemistry, unit 15: kinetics, unit 16: studying for the ap chemistry exam, unit 17: meet the chemistry professional.

Free Printable Chemistry worksheets

Chemistry-focused, free printable Science worksheets for educators to help students discover the fascinating world of chemical reactions, elements, and compounds. Enhance learning experiences with Quizizz!

Recommended Topics for you

• endothermic and exothermic processes
• periodic table
• stoichiometry
• heat transfer and thermal equilibrium
• states of matter and intermolecular forces
• organic chemistry
• chemical equilibrium
• acid base reactions
• atoms and molecules
• alkanes cycloalkanes and functional groups
• chemical bonds
• solutions and mixtures
• alkenes and alkynes
• acids and bases
• redox reactions and electrochemistry
• solids liquids and gases
• equilibrium constant and reaction quotient
• electrolysis and faradays law
• electronic structure of atoms
• elements and compounds

10th - 12th

11th - 12th

Explore Worksheets by Grade

• kindergarten

Explore Chemistry Worksheets by Topics

Explore worksheets by subjects.

• Social studies
• Social emotional
• Foreign language
• Reading & Writing

Explore printable Chemistry worksheets

Chemistry worksheets are an essential tool for teachers to engage their students in the fascinating world of science. These educational resources provide a structured and organized approach to learning various chemistry concepts, from the periodic table to chemical reactions, and everything in between. By incorporating chemistry worksheets into their lesson plans, teachers can ensure that students gain a thorough understanding of the subject matter, while also developing their critical thinking and problem-solving skills. Furthermore, these worksheets cater to different learning styles, making it easier for teachers to differentiate instruction and meet the diverse needs of their students. In conclusion, chemistry worksheets are a valuable asset for teachers looking to create an engaging and effective science curriculum.

Quizizz is an innovative platform that offers a wide range of educational resources, including chemistry worksheets, to help teachers create interactive and engaging learning experiences for their students. In addition to worksheets, Quizizz provides teachers with a plethora of other offerings such as quizzes, flashcards, and interactive games, all designed to reinforce key concepts and make learning fun. By incorporating Quizizz into their lesson plans, teachers can easily track student progress and identify areas where additional support may be needed. Furthermore, the platform is compatible with various devices, making it accessible to students both in the classroom and at home. With Quizizz, teachers can transform their science curriculum into an exciting and immersive learning experience that students will love.

WorkSheets Buddy

Download Math, Science, English and Many More WorkSheets

CBSE Worksheets for Class 10 Chemistry

CBSE Worksheets for Class 10 Chemistry: One of the best teaching strategies employed in most classrooms today is Worksheets. CBSE Class 10 Chemistry Worksheet for students has been used by teachers & students to develop logical, lingual, analytical, and problem-solving capabilities. So in order to help you with that, we at WorksheetsBuddy have come up with Kendriya Vidyalaya Class 10 Chemistry Worksheets for the students of Class 10. All our CBSE NCERT Class 10 Chemistry practice worksheets are designed for helping students to understand various topics, practice skills and improve their subject knowledge which in turn helps students to improve their academic performance. These chapter wise test papers for Class 10 Chemistry will be useful to test your conceptual understanding.

Board: Central Board of Secondary Education(www.cbse.nic.in) Subject: Class 10 Chemistry Number of Worksheets: 25

CBSE Class 10 Chemistry Worksheets PDF

All the CBSE Worksheets for Class 10 Chemistry provided in this page are provided for free which can be downloaded by students, teachers as well as by parents. We have covered all the Class 10 Chemistry important questions and answers in the worksheets which are included in CBSE NCERT Syllabus. Just click on the following link and download the CBSE Class 10 Chemistry Worksheet. CBSE Worksheets for Class 10 Chemistry can also use like assignments for Class 10 Chemistry students.

• CBSE Worksheets for Class 10 Chemistry Acids, Bases And Salts Assignment 1
• CBSE Worksheets for Class 10 Chemistry Acids, Bases And Salts Assignment 2
• CBSE Worksheets for Class 10 Chemistry All Chapters Assignment
• CBSE Worksheets for Class 10 Chemistry Carbon And Its Compound Assignment
• CBSE Worksheets for Class 10 Chemistry Carbon And Its Compounds Assignment
• CBSE Worksheets for Class 10 Chemistry Chemical Reactions And Equations Assignment 1
• CBSE Worksheets for Class 10 Chemistry Chemical Reactions And Equations Assignment 2
• CBSE Worksheets for Class 10 Chemistry Chemical Reactions And Equations Assignment 3
• CBSE Worksheets for Class 10 Chemistry Metals And Non-Metals Assignment 1
• CBSE Worksheets for Class 10 Chemistry Metals And Non-Metals Assignment 2
• CBSE Worksheets for Class 10 Chemistry Periodic Classification of element Assignment 1
• CBSE Worksheets for Class 10 Chemistry Periodic Classification of element Assignment 2
• CBSE Worksheets for Class 10 Chemistry Metals and Non-Metals
• CBSE Worksheets for Class 10 Chemistry SA1 Assignment 1
• CBSE Worksheets for Class 10 Chemistry SA2 Assignment 2
• CBSE Worksheets for Class 10 Chemistry Assignment 1
• CBSE Worksheets for Class 10 Chemistry Assignment 2
• CBSE Worksheets for Class 10 Chemistry Assignment 3
• CBSE Worksheets for Class 10 Chemistry Assignment 4
• CBSE Worksheets for Class 10 Chemistry Assignment 5
• CBSE Worksheets for Class 10 Chemistry Assignment 6
• CBSE Worksheets for Class 10 Chemistry Assignment 7
• CBSE Worksheets for Class 10 Chemistry Assignment 8
• CBSE Worksheets for Class 10 Chemistry Assignment 9
• CBSE Worksheets for Class 10 Chemistry Assignment 10
• CBSE Worksheets for Class 10 Chemistry Assignment 11

Advantages of CBSE Class 10 Chemistry Worksheets

• By practising NCERT CBSE Class 10 Chemistry Worksheet , students can improve their problem solving skills.
• Helps to develop the subject knowledge in a simple, fun and interactive way.
• No need for tuition or attend extra classes if students practise on worksheets daily.
• Working on CBSE worksheets are time-saving.
• Helps students to promote hands-on learning.
• One of the helpful resources used in classroom revision.
• CBSE Class 10 Chemistry Workbook Helps to improve subject-knowledge.
• CBSE Class 10 Chemistry Worksheets encourages classroom activities.

Worksheets of CBSE Class 10 Chemistry are devised by experts of WorksheetsBuddy experts who have great experience and expertise in teaching Maths. So practising these worksheets will promote students problem-solving skills and subject knowledge in an interactive method. Students can also download CBSE Class 10 Chemistry Chapter wise question bank pdf and access it anytime, anywhere for free. Browse further to download free CBSE Class 10 Chemistry Worksheets PDF .

Now that you are provided all the necessary information regarding CBSE Class 10 Chemistry Worksheet and we hope this detailed article is helpful. So Students who are preparing for the exams must need to have great solving skills. And in order to have these skills, one must practice enough of Class 10 Chemistry revision worksheets . And more importantly, students should need to follow through the worksheets after completing their syllabus.  Working on CBSE Class 10 Chemistry Worksheets will be a great help to secure good marks in the examination. So start working on Class 10 Chemistry Worksheets to secure good score.

CBSE Worksheets For Class 10

Share this:.

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Leave a Comment Cancel reply

Notify me of follow-up comments by email.

Notify me of new posts by email.

Lembar Aktivitas 1.6 dan 1.7

Loading ad...

Dwi Agusningtyas

• Google Classroom
• Microsoft Teams
• Download PDF

Chemistry Worksheet Class 11 on Chapter 1 Some Basic Concepts of Chemistry with Answers - Set 1

Chemistry is defined as the branch of science that studies the composition, structure, and properties of matter, as well as the changes that matter undergoes under various conditions and the laws that govern these changes.

Chemistry, as fundamental science, is used in every aspect of a person’s life, from the food consumed to the products used. The advancement of chemical science has altered the foundation of current medicine. Marvel drugs such as penicillin and streptomycin have been developed as a result of ongoing chemistry research.

Download PDF of Class 11 Chemistry Chapter 1 Some Basic Concepts of Chemistry– Set 1

Download PDF

CBSE Class 11 Chemistry Worksheet Chapter 1 Some Basic Concepts of Chemistry – Set 1

Q1. At the same temperature and pressure, an equal volume of gases contains the same number of ____.

a.) Molecules

b.) Electrons

c.) Protons

d.) Particles

Q2. The gas law that relates the volume of a gas to the number of molecules of the gas is ____.

a.) Gay–Lussac’s law

b.) Avogadro’s law

c.) Boyle’s law

d.) Charle’s law

Q3. The mass % of carbon in CO 2 is ____.

Q4. The empirical formula of benzene is ____.

b.) C 6 H 6

c.) C 3 H 3

d.) C 2 H 2

Q5. What is the mole fraction of the solute in a 1.00 molal aqueous solution?

a.) 0.00177

Q6. State the number of significant figures in each of the following numbers:

ii.) 0.00368

iv.) 3.63 × 10 4

Q7. What are the laws of chemical combination?

Q8. What are the applications of Avogadro’s law?

Q9. Calculate the number of Cl – ions in 100ml of 0.001 M HCl solution.

Q10. Perform the following calculations and express the results to the proper number of significant figures:

i.) 144.3m 2 + (254 m × 8.4 m)

ii.) (4.05 × 10 2 mL) – (0.0225 × 10 2 mL)

iii.) (3.50 × 10 2 cm) (4.00× 10 6 cm)

Q11. Write the balanced chemical equations for the following reactions:

i.) Manganese dioxide and concentrated hydrochloric acid.

ii.) Sodium thiosulphate and iodine.

iii.) Copper and dilute nitric acid.

iv.) Sulphur dioxide and hydrogen sulphide.

Q12. Will the molarity of a solution at 50℃ be the same, less or more than the molarity at 25℃?

Q13. Boron occurs in nature in the form of two isotopes having atomic mass 10 and 11. What are the percentage abundances of two isotopes in a sample of boron having an average atomic mass of 10.8?

Q14. How is mole related to the following?

ii.) Volume

iii.) The number of molecules of a substance

Q15. What is cheaper?

40% HCl at the rate of ₹6 per kg or 80% H 2 SO 4 at the rate of ₹3.5 per kg required to neutralise 7 kg of KOH.

Q16. A tennis ball was observed to travel at a speed of 96 miles per hour. Calculate the speed of the ball in metres per second.

Q17. Write short notes on

i.) Limiting reagent

ii.) Avogadro hypothesis

iii.) Dalton’s atomic theory

Q18. Carbon and oxygen are known to form two compounds. The carbon content in one of these compounds is 42.9%, while in the other, it is 27.3%. Show that the data are in agreement with the law of multiple proportions.

Q19. Balance the following equations by partial equation method:

i.) NaOH + Cl 2 → NaCl + NaClO 3 + H 2 O

ii.) C + H 2 SO 4 → CO 2 + SO 2 + H 2 O

iii.) P 4 + HNO 3 → H 3 PO 4 + NO 2 + H 2 O

Butyric acid contains only C, H, and O. A 4.24 mg sample of butyric acid is completely burnt. It gives 8.45 mg of carbon dioxide and 3.46 mg of water.

a.) What is the mass percentage of each element in butyric acid?

b.) Determine its empirical formula.

c.) The molecular mass of butyric acid was determined by the experiment to be 88𝜇. What is the molecular formula?

Download PDF to access answers of the Chemistry Worksheet for Class 11 Chemistry Chapter 1 Some Basic Concepts of Chemistry Set – 1. Download PDF

• Class 11 Chemistry Chapter 1 Some Basic Concepts of Chemistry MCQs
• Important Questions for Class 11 Chemistry Chapter 1 Some Basic Concepts of Chemistry
• Chemistry Concept Questions and Answers
• CBSE Class 11 Chemistry Practical
• Significant Figures Chemistry
• Laws of Chemical Combination for Elements and Compounds
• Mole Concept
• Empirical Formula & Molecular Formula

• Share Share

Register with BYJU'S & Download Free PDFs

Register with byju's & watch live videos.

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons

Margin Size

• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

Mathematics and Measurements 1 (Worksheet)

• Last updated
• Save as PDF
• Page ID 90888

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

\( \newcommand{\Span}{\mathrm{span}}\)

\( \newcommand{\id}{\mathrm{id}}\)

\( \newcommand{\kernel}{\mathrm{null}\,}\)

\( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\)

\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\)

\( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

\( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vectorC}[1]{\textbf{#1}} \)

\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

Name: ______________________________

Section: _____________________________

Student ID#:__________________________

Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

“Anything worth measuring is worth measuring well.”

Source unknown

To determine if a runner broke the world’s record for a marathon, you must carefully measure the time that passed between the start and finish of the race and compare it to the record time for that marathon. Since time can be measured and expressed as an amount, it is called a quantity. Ten seconds, two minutes, and five hours are examples of quantities of time. Other familiar quantities that are important in chemistry include mass (similar to the more familiar weight), length, volume, and density.

The International System of Units

In 1960, a group of scientists from many fields and many countries agreed upon a set of metric units that would serve as a standard for scientific communication. This standard set of units is known as the International System of Units and is abbreviated SI (the abbreviation is derived from the French spelling le Systeme International d’ Unites ). Seven quantities are the foundation for SI, and each has a base unit in which that quantity is expressed. Table 1 lists the base units for length, mass, volume, temperature, time and chemical amount, along with their abbreviations and their relationships to common United States units.

Table 1: Seven fundamental units in the SI system. All other units can be decomposed to these units

Table 2: SI Base Units Equivalents

The three SI base units for mass, volume and length in Table 1 were chosen because they correspond to magnitudes which are convenient for everyday measurement. They are well suited for measurements on a scale that we can directly relate to. However, chemists often work with tiny quantities such as those used to express the diameter of a hydrogen atom or huge quantities such as the number of particles in a kilogram of carbon. These numbers are beyond the range of our senses and cannot be conveniently expressed in standard notation in SI units. Thus, the system of scientific notation is used to express very small and very large quantities. Scientific notation is a method of expressing numbers as a product of two factors. The first factor is a number that is greater than or equal to 1 but less than 10. The second factor is 10 raised to a power. The power of 10, or exponent, is positive for numbers greater than 10 and negative for numbers less than 1. Table 2 gives examples showing both the ordinary decimal form and the exponential form for some quantities. Notice how scientific notation eliminates the need to write a long list of zeros in very small and very large numbers. Table 2. Examples of Quantities Expressed in Scientific Notation

Metric Prefixes

To further simplify the expression of measured quantities, scientists use prefixes with metric units to represent powers of ten. The following Tables list metric prefixes with a range of 25 orders of magnitude and those frequently used in chemistry. Notice that each prefix has an abbreviation and an equivalent power of ten. You should know those prefixes in bold face italics and their associated powers of ten listed in Table 3. You may need to memorize them if you can't remember them.

Table 3. Commonly used prefixes and Equivalent Powers of Ten. Know the bold italics.

Mathematical Operations in Scientific Notation

Addition and subtraction.

To add or subtract numbers that are expressed in scientific notation, use the “enter exponent” key on your calculator to express the power of ten. It is usually labeled “EE” or “EXP.” Do not use the 10 x or y x key for scientific notation exponents. The calculator usually will express the result in scientific notation automatically. For example: 3.25 x 10 3 + 4.66 x 10 4 = Calculator key sequence: 3 . 2 5 EE 3 + 4 . 6 6 EE 4 = Result: 4.985 x 10 4

Multiplication

To multiply numbers that are expressed in scientific notation, use your calculator. For example: (3.1 x 10 2 ) x (5.2 x 10 4 ) = Calculator key sequence: 3 . 1 EE 2 ¥ 5 . 2 EE 4 = Result: 1.612 x 10 7

To divide numbers that are expressed in scientific notation, again, let your calculator do the work. For example: (7.5 x 10 2 ) / (5.9 x 10 –4 ) = Calculator key sequence: 7 . 5 EE 2 ÷ 5 . 9 EE 4 +/– = Result: 1.271... x 10 6

To raise a number expressed in scientific notation to a power, use the yx key on your calculator. For example: (2.5 x 10 2 ) 3 = Calculator key sequence: 2 . 5 EE 2 yx 3 = Result: 1.5625 x 10 7

Measured Quantities and Significant Figures

There is a degree of uncertainty in every measurement, and this uncertainty, by convention, is reflected in the last recorded digit of any measured quantity. If several people measure the same distance with a ruler, their measurements will probably differ in the last digit. However, these measurements will cluster around the true value. Some will be equal to the true value, some will be higher, and some will be lower. The average of a series of measurements is generally considered to be the most accurate value. The number of significant figures in a measurement is the total of the number of digits known with certainty plus the one uncertain digit. The digits known with certainty are those that can be read precisely from the measuring instrument. The last digit recorded in any measured quantity—the uncertain digit—is estimated. When a measurement is written in scientific notation, the first factor represents the significant digits in the measured quantity. The second factor, the power of ten, represents the magnitude of the measurement, or the number of decimal places, and therefore has nothing to do with the number of significant figures in the quantity. If the three-significant-figure measured quantity 134 pounds is written in scientific notation as 1.34 x 10 2 pounds, the number of significant figures cannot change, so this must also have three significant figures. The following rules summarize the conventions used by chemists when working with measured quantities:

• The last digit expressed in a measured quantity is the uncertain, or estimated, digit.
• Zeros that serve as place holders in ordinary decimal notation are not significant. For example, the measured quantity 0.001 m has one significant figure. This becomes more apparent when we write the quantity in scientific notation: 1 x 10 –3 m.
• When adding and subtracting numbers representing measured quantities, the number of decimal places in the sum or difference are limited by the number of decimal places in the measured quantity that has the least number of decimal places. For example: 0.152 g + 0.26 g = 0.41 g.
• When multiplying and/or dividing numbers representing measured quantities, the number of significant figures in the result is the number of significant figures in the factor with the least number of significant figures. For example: (1.5 x 10 2 ) x (1.350 x 10 3 ) = 2.0 x 10 5 .