Chemistry Chapter 1: The Central Science
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Questions and Answers

What defines 'matter' in the context of chemistry?

  • Only substances that can undergo chemical changes
  • Anything that has mass and occupies space (correct)
  • Anything that can change state and form
  • Any observable phenomenon in the physical world

Which of the following best describes a substance?

  • A combination of multiple types of atoms
  • Has a definite composition and distinct properties (correct)
  • Can be easily separated into simpler components
  • Always exists in a liquid state

Which of the following is a correct representation of a molecular model?

  • Molecular formula like NaCl
  • A numeric representation of molecular weights
  • An equation showing reactants and products
  • A visual model using different colors for each element (correct)

Which of the following statements correctly defines an element?

<p>Cannot be separated into simpler substances by chemical means (C)</p> Signup and view all the answers

The term 'chemical reaction' is associated with which of the following?

<p>Changes in the arrangement of atoms and molecules (B)</p> Signup and view all the answers

What happens to the state of matter when heat is added to a solid?

<p>It melts into a liquid. (A)</p> Signup and view all the answers

Which temperature scale is considered the absolute scale?

<p>Kelvin (A)</p> Signup and view all the answers

What is the equivalent of 28°C in Kelvin?

<p>298 K (A)</p> Signup and view all the answers

Which of the following describes the relationship for calculating density?

<p>Mass divided by volume. (A)</p> Signup and view all the answers

How is 1 liter defined in terms of volume?

<p>Equal to a cubic decimeter. (D)</p> Signup and view all the answers

Which of the following substances is classified as a compound?

<p>Baking soda (D)</p> Signup and view all the answers

What type of mixture is formed when sugar is dissolved in water?

<p>Homogeneous (D)</p> Signup and view all the answers

Which statement is true about mixtures?

<p>Their components retain distinct identities. (C)</p> Signup and view all the answers

What is the defining characteristic of gases as a state of matter?

<p>Particles assume the shape of their container. (A)</p> Signup and view all the answers

Which of the following is a characteristic of a heterogeneous mixture?

<p>Distinct identities of components (B)</p> Signup and view all the answers

What classification does aluminum foil belong to?

<p>Substance, element (C)</p> Signup and view all the answers

Which of the following examples represents a heterogeneous mixture?

<p>Sugar mixed with iron filings (C)</p> Signup and view all the answers

Which of the following describes the particles in a solid state of matter?

<p>Particles are held together closely in an orderly fashion. (D)</p> Signup and view all the answers

How many significant figures are in the measurement 250 mL?

<p>2 (D)</p> Signup and view all the answers

When performing addition and subtraction, what determines the number of decimal places in the final answer?

<p>The number with the least digits to the right of the decimal point. (C)</p> Signup and view all the answers

If you multiply 1.4 by 8.011, what is the correct final answer when considering significant figures?

<p>11 (B)</p> Signup and view all the answers

What is the mass of three pennies minted after 1982, each with a mass of 2.5 g, and how does the nature of exact numbers affect significant figures?

<p>7.5 g, unlimited significant figures. (A)</p> Signup and view all the answers

What rounding rule should you apply to a number less than 5 when rounding?

<p>Round down. (A)</p> Signup and view all the answers

What distinguishes a chemical property from a physical property?

<p>Chemical properties require changes in identity of a substance. (B)</p> Signup and view all the answers

Which of the following is an example of a physical change?

<p>Ice melting into water. (C)</p> Signup and view all the answers

What is an extensive property?

<p>A property that reflects the size of an object. (A)</p> Signup and view all the answers

Which of the following statements about significant figures is true?

<p>Zeros between non-zero digits are always significant. (D)</p> Signup and view all the answers

In the context of measurements, which of the following is considered an inexact number?

<p>A measured length using a ruler. (A)</p> Signup and view all the answers

How many significant figures are in the number 0.004560?

<p>4 (D)</p> Signup and view all the answers

What happens to a substance after a chemical change?

<p>The original substance no longer exists in its initial form. (C)</p> Signup and view all the answers

Which property can change while leaving the substance's identity intact?

<p>Temperature. (D)</p> Signup and view all the answers

What is the correct rounded result of the addition $105.5 L + 10.65 L$?

<p>116.2 L (B)</p> Signup and view all the answers

In the context of measurements, what does precision refer to?

<p>The reproducibility of measurements (C)</p> Signup and view all the answers

If a student’s measurements are both accurate and precise, what does this mean?

<p>The measurements are close to the true value and close to each other. (D)</p> Signup and view all the answers

What is the term for a fraction that expresses the same quantity in different ways?

<p>Conversion factor (B)</p> Signup and view all the answers

What is the average weight of Student A’s measurements?

<p>0.333 g (D)</p> Signup and view all the answers

Which student’s results are described as neither precise nor accurate?

<p>Student B (D)</p> Signup and view all the answers

In dimensional analysis, what is the purpose of using conversion factors?

<p>To change one measure to another (B)</p> Signup and view all the answers

What is the volume calculated from the dimensions $1.0267 cm, 2.508 cm, 12.599 cm$ rounded to the smallest number of significant figures?

<p>32.44 cm³ (B)</p> Signup and view all the answers

Flashcards

Chemistry

The study of matter and the changes it undergoes.

Matter

Anything that has mass and occupies space.

Substance

A form of matter with a definite, constant composition and distinct properties.

Element

A substance that cannot be broken down into simpler substances by chemical means.

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Compound

A substance formed from two or more elements.

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Mixture

A combination of two or more substances.

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Molecular Formula

A representation of a molecule using chemical symbols and subscripts to show the number of each type of atom.

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Molecular Models

Visual representations of molecules. They can be "ball-and-stick" or "space-fill".

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Compound

Two or more elements chemically combined in fixed ratios.

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Mixture

A physical combination of two or more substances without changing their identities.

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Homogeneous Mixture

A mixture with a uniform composition throughout.

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Heterogeneous Mixture

A mixture with a non-uniform composition.

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Solid

State of matter with particles close together and fixed positions, maintaining shape.

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Liquid

State of matter with particles close together but able to move, taking the shape of the container.

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Gas

State of matter with particles far apart and moving freely, filling the entire container.

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Element

A substance made up of only one type of atom.

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Physical Separation

A process used to separate substances that does not involve a chemical reaction.

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States of matter

Solid, liquid, and gas are the fundamental forms that matter exists in. They can change from one state to another without altering the underlying chemical makeup.

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Interconversion of states

The process of changing between solid, liquid, and gas states, only requiring a change in energy (heat).

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SI base units

A standardized system of measurement units used globally in science and engineering.

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Mass

The amount of matter in an object. It's different from weight, which is the force of gravity on an object.

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Temperature (Celsius)

A measure of how hot or cold something is, based on the freezing and boiling points of water.

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Temperature (Kelvin)

An absolute temperature scale where zero Kelvin represents the absence of heat.

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Temperature (Fahrenheit)

A temperature scale commonly used in the United States.

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Volume

The amount of space occupied by an object.

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Density

A measure of how much mass is contained within a given volume.

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Significant Figures

Used to indicate the precision of a measured value.

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Significant Figures in Addition/Subtraction

The answer has the same number of digits after the decimal point as the measurement with least amount of digits after the decimal point.

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Significant Figures in Multiplication/Division

The answer has the fewest number of significant figures of any of the numbers in the calculation.

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Exact Numbers

Numbers that have an infinite number of significant figures

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Rounding Rules

If the digit is less than 5 round down. If the digit is 5 or greater round up.

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Multiple Step Calculations

Calculations with several steps may require retaining extra digits to prevent accumulating rounding error in the final result.

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Accuracy

How close a measurement is to the true or accepted value.

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Precision

How closely measurements of the same thing are to one another.

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Significant Figures

The number of digits in a measurement that are reliable or meaningful.

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Conversion Factor

A fraction expressing the same quantity in two different units.

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Dimensional Analysis

A problem-solving method using conversion factors to change one measure to another.

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Rounding

Adjusting a number to a specified number of decimal places or significant figures.

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Physical Property

A characteristic that can be observed or measured without changing the substance's chemical composition

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Chemical Property

A property that describes how a substance reacts with other substances to form new substances.

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Physical Change

A change in a substance's physical properties (like its appearance) without changing its chemical composition.

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Chemical Change

A change in which one or more substances are transformed into new substances with different properties.

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Extensive Property

A property that depends on the amount of matter present.

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Intensive Property

A property that is independent of the amount of matter present.

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Exact Numbers

Numbers obtained from defined quantities or by counting.

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Inexact Numbers

Numbers that are measured and have some degree of uncertainty.

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Significant Figures

Used to express the uncertainty in measured values.

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Significant Figures Rule 1

Non-zero digits are always significant.

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Significant Figures Rule 2

Zeros between non-zero digits are significant.

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Significant Figures Rule 3

Leading zeros (to the left of non-zero digits) are not significant.

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Significant Figures Rule 4

Trailing zeros (after non-zero digits) to the right of the decimal point are significant.

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Significant Figures Rule 5

Trailing zeros (after non-zero digits) to the right of the decimal point are not significant if there is no decimal point.

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Study Notes

Chapter 1: Chemistry: The Central Science

  • Chemistry is the study of matter and the changes matter undergoes.
  • Matter is anything that has mass and occupies space.

1.1 The Study of Chemistry

  • Chemistry involves familiar terms: molecules, atoms, and chemical reactions.
  • A familiar chemical formula is Hâ‚‚O.
  • Molecules can be represented in different ways, including molecular formulas and molecular models. Molecular models can be "ball-and-stick" or "space-fill". Each element is represented by a particular color.

Table 1.1: Colors of Elements Commonly Used in Molecular Art

  • Elements are represented by different colors (e.g., hydrogen is white, carbon is black, nitrogen is blue, oxygen is red, fluorine is yellow-green, sodium is light gray, sulfur is yellow, chlorine is lime green, bromine is orange, iodine is purple).

1.2 The Scientific Method

  • Observation: Natural phenomena and measured events. If consistent, a law can be stated.
  • Hypothesis: A tentative explanation to explain the observations
  • Experiment: Tests the hypothesis by manipulating one variable.
  • Model (Theory): Based on accumulated experiments. Explains existing data and predicts new events.
  • Observations do not always support the hypothesis, revision may happen

1.3 Classification of Matter

  • Matter can be either a substance or a mixture of substances.
  • A substance can be an element or a compound.
    • Substances have a definite (constant) composition and distinct properties.
    • Examples: sodium chloride, water, oxygen.
  • Elements cannot be separated into simpler substances by chemical means.
    • Examples: iron, mercury, oxygen, hydrogen.
  • Compounds are two or more elements chemically combined in definite ratios. Compounds cannot be separated by physical means.
    • Examples: salt, water, carbon dioxide.
  • Mixtures have a varying composition and their components retain their identities. Mixtures can be separated by physical means.
    • Examples: sugar/iron, sugar/water.
  • Mixtures can be homogeneous (uniform composition throughout, e.g., sugar dissolved in water) or heterogeneous (non-uniform composition, e.g., sugar mixed with iron filings).

States of Matter

  • Solids have particles close together in an ordered fashion with little freedom of motion; solid samples don't conform to their container.
  • Liquids have particles close together but not rigidly in position; particles move past each other; liquid samples conform to the shape of the container they are in.
  • Gases have particles randomly spread apart and have complete freedom of movement; gas samples occupy the entire volume of the container.

1.3 Scientific Measurement

  • SI base units: Used to measure quantitative properties of matter.
    • Length: meter (m)
    • Mass: kilogram (kg)
    • Time: second (s)
    • Electric current: ampere (A)
    • Temperature: kelvin (K)
    • Amount of substance: mole (mol)
    • Luminous intensity: candela (cd)

SI Prefixes

  • Prefixes are used to indicate multiples or fractions of SI units.

1.4 Properties of Matter

  • Quantitative Measurements: Expressed using numbers. Example: 25 mL of water.
  • Qualitative Observations: Expressed using a property. Example: yellow color.
    • Physical properties: Observable without changing the substance. Example: color, melting point, states of matter
    • Physical changes: Identity of the substance stays the same. Changes in state of matter, melting and freezing.
    • Chemical properties: properties that are determined by the chemical changes observed, example: flammability, acidity, corrosiveness, reactivity. Chemical changes are when original substance is altered
  • Extensive properties depend on the amount of matter. Examples include mass, length.
  • Intensive properties do not depend on the amount of matter. Examples include density, temperature, color.

1.5 Uncertainty in Measurement

  • Exact numbers: Have defined values. Example: counting numbers, conversion factors.
  • Inexact numbers: Obtained by methods other than counting. Example: measured values.
  • Significant figures: Used to express uncertainty in inexact numbers.

Guidelines for Significant Figures

  • Non-zero digits are significant.
  • Zeros between non-zero digits are significant.
  • Zeros to the left of the first non-zero digit are not significant.
  • Zeros to the right of the last non-zero digit are significant if a decimal point is present. Otherwise, they are not significant.

Calculations with Measured Numbers

  • Addition/Subtraction: Result has same number of digits after the decimal place as the number with the fewest digits after the decimal.
  • Multiplication/Division: Result has the same number of significant figures as the number with the fewest significant figures.

Multiple-Step Calculations

  • Retain one or more extra digits in preliminary steps to reduce rounding error.

1.6 Using Units and Solving Problems

  • Conversion Factors: Fractions expressing the same quantity in different units.
  • Dimensional analysis: Employing conversion factors to change units.

Notes on Problem Solving

  • Carefully read the problem.
  • Identify given information and what is asked for.
  • Recall relevant formulas, constants, conversion factors.
  • Check for appropriate units and significant figures.
  • Evaluate your result for reasonableness.

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Chapter 1 Chemistry: The Central Science PDF

Description

Explore the foundational concepts of chemistry in Chapter 1, where matter, molecules, and the scientific method are introduced. Understand the significance of chemical formulas and the visual representation of elements in molecular models. This quiz will challenge your knowledge of basic chemistry principles and terminology.

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