Chemistry Chapter 2 Measurements and Calculations
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Questions and Answers

What is a logical approach to solving problems by observing and collecting data called?

scientific method

What is the use of the senses to obtain information?

observing

What does observation involve?

making measurements and collecting data

What are the two types of data?

<p>qualitative and quantitative</p> Signup and view all the answers

Numerical information, for example, a mass of copper ore is 25.7 grams, is what kind of data?

<p>quantitative</p> Signup and view all the answers

Non-numerical information, such as 'the sky is blue,' is what kind of data?

<p>qualitative</p> Signup and view all the answers

What does experimenting involve?

<p>carrying out procedure under controlled conditions to make observations and collect data</p> Signup and view all the answers

What is a specific portion of matter in a given region of space that has been selected for study during an experiment?

<p>system</p> Signup and view all the answers

What are statements that apply to a range of information called?

<p>generalizations</p> Signup and view all the answers

Scientists use generalizations about data to formulate a _____________, or a testable statement.

<p>hypothesis</p> Signup and view all the answers

What does testing a hypothesis require?

<p>experimentation that provides data to support or refute a hypothesis or theory</p> Signup and view all the answers

What are controls?

<p>during testing, the experimental conditions that remain constant</p> Signup and view all the answers

What are variables?

<p>any condition that changes during experimental testing</p> Signup and view all the answers

If testing reveals that predictions were not correct, the hypothesis must be _______ or ________.

<p>discarded; modified</p> Signup and view all the answers

A __________ in science is more than a physical object; it can be an explanation of how phenomena occur.

<p>model</p> Signup and view all the answers

What is one important model in chemistry and what does it state?

<p>the atomic model of matter that states that matter is composed of tiny particles called atoms</p> Signup and view all the answers

If a model successfully explains many phenomena, it may become part of a ________.

<p>theory</p> Signup and view all the answers

What is a theory?

<p>a broad generalization that explains a body of facts or phenomena</p> Signup and view all the answers

When is a theory considered successful?

<p>If they can predict the results of many new experiments</p> Signup and view all the answers

Measurements are ______ information that represent _________.

<p>quantitative; quantities</p> Signup and view all the answers

A ___________ is something that has magnitude, size, or amount.

<p>quantity</p> Signup and view all the answers

Units of measurement compare what is to be measured with a previously defined size. Nearly every measurement is a number plus a _______.

<p>unit</p> Signup and view all the answers

Scientists all over the world have agreed on a single measurement system called Le Systeme International d'Unites, abbreviated?

<p>SI</p> Signup and view all the answers

The SI system was adopted in 1960 by who?

<p>General Conference on Weights and Measurements</p> Signup and view all the answers

How many base units does SI have?

<p>7</p> Signup and view all the answers

SI units are defined in terms of?

<p>standards of measurement</p> Signup and view all the answers

What are the standards?

<p>objects or natural phenomena that are of constant value</p> Signup and view all the answers

In the U.S. the ____________ plays the main role in maintaining standards and setting style conventions.

<p>National Institute of Standards and Technology</p> Signup and view all the answers

Name and put in order the stages in the scientific method.

<p>observing, formulate hypothesis, test, theorize, and publish results</p> Signup and view all the answers

Prefixes are added to the names of the SI base units to represent?

<p>quantities that are larger or smaller than the base units</p> Signup and view all the answers

Mass is?

<p>a measure of the quantity of matter</p> Signup and view all the answers

What is the SI standard unit for mass?

<p>kilogram</p> Signup and view all the answers

_______ are used for the mass of small objects; 1 _______ is about the mass of a paper clip.

<p>grams; gram</p> Signup and view all the answers

For smaller objects, the ________ is used.

<p>mg</p> Signup and view all the answers

One milligram is ______ of a gram or ____________ of a kilogram.

<p>1/1000; 1/1000000</p> Signup and view all the answers

Mass is the measure of the amount of matter. ____________ is a measure of the gravitational pull on matter.

<p>weight</p> Signup and view all the answers

Mass is determined by?

<p>comparing the mass of an object with a set of standard masses on two sides of a balance</p> Signup and view all the answers

Unlike weight, mass does not depend on?

<p>gravity</p> Signup and view all the answers

Mass is measured on instruments such as?

<p>balance</p> Signup and view all the answers

Weight is typically measured on a?

<p>spring scale</p> Signup and view all the answers

The weight of an object on the Moon is about?

<p>1/6</p> Signup and view all the answers

What is the standard unit for length?

<p>meter</p> Signup and view all the answers

To express longer distances the _____ is used.

<p>km</p> Signup and view all the answers

To express shorter distances the ___________ is used; and is equal to _______ of a meter.

<p>cm; 1/100</p> Signup and view all the answers

Combinations of SI base units form?

<p>derived units</p> Signup and view all the answers

Derived units are produced by?

<p>multiplying or dividing standard units</p> Signup and view all the answers

_______, Pa, is given to combination kg/m(s^2).

<p>pascal</p> Signup and view all the answers

________ the amount of space occupied by an object; the derived SI unit of volume is _____

<p>volume; m^3</p> Signup and view all the answers

When chemists measure volumes of liquids and gases, they often use a non-SI unit called ____ which is equivalent to 1 decimeter.

<p>liter</p> Signup and view all the answers

__________ is the ratio of mass to volume, or mass divided by volume.

<p>density</p> Signup and view all the answers

The ratio of mass to volume is?

<p>constant</p> Signup and view all the answers

Density is one property that can help identify a?

<p>substance</p> Signup and view all the answers

The density varies with?

<p>temperature</p> Signup and view all the answers

Density usually decreases with?

<p>increasing temperature</p> Signup and view all the answers

_______ a ratio derived from the equality between two different units that can be used to convert from one unit to the other.

<p>conversion factor</p> Signup and view all the answers

Because conversion factors are equal to 1, they can be multiplied by other factors in equations without changing the?

<p>validity of the equations</p> Signup and view all the answers

________ is a mathematical technique that allows you to use units to solve problems involving measurements.

<p>dimensional analysis</p> Signup and view all the answers

When you want to use a conversion factor to change a unit in a problem in the following way: ______________________

<p>quantity sought= quantity given x conversion factor</p> Signup and view all the answers

You can derive conversion factors if you know the relationship between the _______________ and ___________.

<p>unit you have; unit you want</p> Signup and view all the answers

____________ refers to the closeness of measurements to the correct or accepted value of the quantity measured.

<p>accuracy</p> Signup and view all the answers

____________ refers to the closeness of a set of measurements of the same quantity made in the same way.

<p>precision</p> Signup and view all the answers

The accuracy of an individual value or of an average experimental value can be compared quantitatively with?

<p>correct or accepted value by calculating the percentage error</p> Signup and view all the answers

_______________________ is calculated by subtracting the accepted value from the experimental value, dividing the difference by the accepted value, and then multiplying by 100.

<p>percentage error</p> Signup and view all the answers

The percentage error has a __________ value if the accepted value is greater than the experimental value.

<p>negative</p> Signup and view all the answers

The percentage error has a __________ value if the accepted value is less than the experimental value.

<p>positive</p> Signup and view all the answers

____________ in a measurement consist of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated.

<p>significant figures</p> Signup and view all the answers

Zeros appearing between non-zero digits are?

<p>significant</p> Signup and view all the answers

Zeros appearing in front of all non-zero digits are?

<p>insignificant</p> Signup and view all the answers

Zeros at the end of a number and to the right of a decimal point are?

<p>significant</p> Signup and view all the answers

Zeros at the end of a number but to the left of a decimal point may or may not be?

<p>significant</p> Signup and view all the answers

If the digit following the last digit to be retained is greater than 5, then the last digit should be?

<p>increased by 1</p> Signup and view all the answers

If the digit following the last digit to be retained is less than 5, then the last digit should?

<p>stay the same</p> Signup and view all the answers

If the digit following the last digit to be retained is 5, followed by nonzero digit(s), the last digit should?

<p>be increased by 1</p> Signup and view all the answers

If the digit following the last digit to be retained is 5, not followed by nonzero digit(s) and preceded by an odd digit, then the last digit should be?

<p>increased by 1</p> Signup and view all the answers

If the digit following the last digit to be retained is 5, not followed by nonzero digit(s) and the preceding significant digit is even, then the last digit should?

<p>stay the same</p> Signup and view all the answers

When adding or subtracting decimals, the answer must have the ______ number of digits to the ______ of the decimal point as there are in the measurement having the fewest digits to the ______ of the decimal point.

<p>same; right; right</p> Signup and view all the answers

For multiplication or division, the answer can have no more significant figures than are in the measurement with the ____________ number of significant figures.

<p>fewest</p> Signup and view all the answers

_____________ numbers are written in the form M x 10^n, where the factor M is a number greater than or equal to 1 but less than 10.

<p>scientific notation</p> Signup and view all the answers

In scientific notation M x 10^n. Determine M by moving the decimal point to the _________ to the left or right so that only one _________ digit remains to the left of the decimal point.

<p>original treatment; nonzero</p> Signup and view all the answers

Example of addition using scientific notation.

<p>4.2 x 10^4 kg + 0.79 x 10^4 kg = 4.99 x 10^4 kg rounded to 5.0 x 10^4 kg</p> Signup and view all the answers

Example of multiplication using scientific notation.

<p>5.23 x 10^6 um by 7.1 x 10^-2 um = 3.7 x 10^5 um^2</p> Signup and view all the answers

Example of division using scientific notation.

<p>5.44 x 10^7 g / 8.1 x 10^4 mol = 6.7 x 10^2 g/mol</p> Signup and view all the answers

What are the steps to solving such types of problems?

<p>analyze, plan, solve, check work</p> Signup and view all the answers

Explain 4 steps in solving a problem.

<ol> <li>Read the problem at least twice and analyze the information. 2. Develop a plan for solving the problem. 3. Substitute data and necessary conversion factors into the plan you have developed. 4. Examine the answer to determine whether it is reasonable.</li> </ol> Signup and view all the answers

When two quantities are __________ to each other if dividing by one another gives a constant value.

<p>directly proportional</p> Signup and view all the answers

Direct proportion can be expressed as?

<p>y=kx</p> Signup and view all the answers

Inverse proportion can be expressed as?

<p>xy=k</p> Signup and view all the answers

Which mass is the largest? 0.200g; 0.020kg; 20.0mg; 2000ug

<p>0.020kg</p> Signup and view all the answers

What contains 3 significant digits?

<p>20.2 mL</p> Signup and view all the answers

Theory differs from hypothesis in that a theory?

<p>has been subjected to experimental testing</p> Signup and view all the answers

All measurements in science?

<p>have some degree of uncertainty</p> Signup and view all the answers

When numbers are multiplied or divided, the answer can have no more?

<p>significant figures than are in the measurement that has the smallest number of significant figures.</p> Signup and view all the answers

Which of the following is not part of the scientific method? making measurements, introducing bias, making an educated guess, analyzing data

<p>introducing bias</p> Signup and view all the answers

The accuracy of a measurement is?

<p>how close it is to the true value</p> Signup and view all the answers

A measurement of 23465 mg converted to grams equals ________.

<p>23.465 g</p> Signup and view all the answers

A metal sample has a mass of 45.65 g. The volume of the sample is 16.9 cm^3. The density of the sample is?

<p>2.70 g/cm^3</p> Signup and view all the answers

A recipe for 18 cookies calls for 1 cup of chocolate chips. How many cups of chocolate chips are needed for 3 dozen cookies? What kind of proportion, direct or indirect, did you use to answer this question?

<p>2 cups; direct proportion</p> Signup and view all the answers

Which contains exact numbers? There are 12 eggs in a dozen; the accident injured 21 people; the circumference of the Earth at the equator is 40000 km.

<p>There are 12 eggs in a dozen; the accident injured 21 people</p> Signup and view all the answers

Study Notes

Scientific Method

  • Involves a logical problem-solving approach: observing, collecting data, formulating hypotheses, testing, and formulating theories based on data.
  • Key elements: observation, experimentation, and theorizing.

Types of Data

  • Data can be classified as qualitative (non-numerical) or quantitative (numerical).
  • Examples:
    • Quantitative: mass of an object (e.g., 25.7 grams).
    • Qualitative: descriptive information (e.g., "the sky is blue").

Experimentation

  • Experiments are conducted under controlled conditions to collect data.
  • Systems refer to specific portions of matter selected for study.

Hypotheses and Theories

  • A hypothesis is a testable statement based on generalizations about data.
  • Successful theories can predict outcomes of new experiments and explain a range of phenomena.

Measurements

  • Quantitative information represents quantities and is distinct from general quantities.
  • SI (International System of Units) is the standard measurement system globally, adopted in 1960.

Units of Measurement

  • SI has 7 base units, such as meters for length and kilograms for mass.
  • Prefixes modify the size of units to indicate larger or smaller quantities.

Mass and Weight

  • Mass measures the amount of matter, while weight measures the gravitational pull on that matter.
  • Mass is determined using a balance, and it remains constant regardless of gravity.

Length and Volume

  • The standard unit for length is the meter; kilometers measure longer distances, while centimeters measure shorter ones.
  • Volume commonly uses liters for liquids and gases; derived SI unit is cubic meters.

Density

  • Density is the ratio of mass to volume, a constant property that can help identify substances, varying with temperature.

Conversion Factors and Dimensional Analysis

  • Conversion factors relate different units and can be used in dimensional analysis to solve measurement problems.
  • Dimensional analysis ensures units are consistent and helps derive conversion factors.

Accuracy and Precision

  • Accuracy refers to how close a measurement is to the true value; precision refers to consistency in measurements.
  • Percentage error quantifies accuracy, calculated by the difference between experimental and accepted values.

Significant Figures

  • Significant figures reflect precision in measurements, including all known digits plus one estimated digit.
  • Rules govern the treatment of zeros in significant figures and rounding based on the following digits.

Mathematical Operations with Measurements

  • When adding/subtracting, results must match the least number of decimal places in the measurements; multiplication/division limits results to the least number of significant figures.

Scientific Notation

  • Numbers in scientific notation are expressed as M x 10^n, simplifying large values and facilitating calculations.

Problem Solving in Science

  • Steps: analyze the problem, plan a solution, substitute values, and verify the answer.
  • Direct and inverse proportions describe relationships between quantities, essential for solving problems.

Common Measurement Conversions

  • Conversions include mass from milligrams to grams (1 mg = 1/1000 g) and common mass comparisons.

Exact Numbers and Measurements

  • Exact numbers have no uncertainty; examples include counts (12 eggs in a dozen) versus measured values (e.g., an accident statistic).
  • Every scientific measurement has some degree of uncertainty, affecting the accuracy and precision of experimental results.

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