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Questions and Answers
Which of the following elements is represented by the symbol 'Pb'?
Which of the following elements is represented by the symbol 'Pb'?
What percentage of the Earth’s crust by mass is comprised of only five specific elements?
What percentage of the Earth’s crust by mass is comprised of only five specific elements?
What does the Law of Constant Composition state about compounds?
What does the Law of Constant Composition state about compounds?
Which type of mixture has a uniform composition throughout?
Which type of mixture has a uniform composition throughout?
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Which of the following is an example of a physical property?
Which of the following is an example of a physical property?
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Which of the following is NOT a type of property of matter?
Which of the following is NOT a type of property of matter?
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What type of property is mass considered to be?
What type of property is mass considered to be?
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What happens during a chemical change?
What happens during a chemical change?
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Which element is represented by the symbol 'Ag' and is derived from Latin?
Which element is represented by the symbol 'Ag' and is derived from Latin?
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Which process can be used to separate a mixture based on differences in boiling points?
Which process can be used to separate a mixture based on differences in boiling points?
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What distinguishes a heterogeneous mixture from a homogeneous mixture?
What distinguishes a heterogeneous mixture from a homogeneous mixture?
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What are elements commonly represented by?
What are elements commonly represented by?
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Which of the following is a characteristic of intensive properties?
Which of the following is a characteristic of intensive properties?
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Why is the ability to burn considered a chemical property?
Why is the ability to burn considered a chemical property?
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When ice melts to form water, what type of change is occurring?
When ice melts to form water, what type of change is occurring?
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What is a method you would use for separating a solid from a liquid in a mixture?
What is a method you would use for separating a solid from a liquid in a mixture?
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What is the primary focus of chemistry?
What is the primary focus of chemistry?
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Which state of matter is represented by water vapor?
Which state of matter is represented by water vapor?
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What distinguishes an element from a compound?
What distinguishes an element from a compound?
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Atoms are described as what in the context of matter?
Atoms are described as what in the context of matter?
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Which of the following statements about substances is correct?
Which of the following statements about substances is correct?
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Which best describes a compound?
Which best describes a compound?
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What term is used for groups of atoms connected together in nature?
What term is used for groups of atoms connected together in nature?
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Which statement regarding the classification of matter is inaccurate?
Which statement regarding the classification of matter is inaccurate?
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What is the purpose of dimensional analysis in measurements?
What is the purpose of dimensional analysis in measurements?
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When performing dimensional analysis, why is it important to set up a ratio of comparison?
When performing dimensional analysis, why is it important to set up a ratio of comparison?
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Which of the following is an example of a conversion factor?
Which of the following is an example of a conversion factor?
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What happens when you apply multiple conversions in dimensional analysis?
What happens when you apply multiple conversions in dimensional analysis?
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What is a common misconception about dimensional analysis?
What is a common misconception about dimensional analysis?
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What is the primary focus of measuring precision in scientific experiments?
What is the primary focus of measuring precision in scientific experiments?
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In the context of significant figures, which statement is true regarding zeroes at the beginning of a number?
In the context of significant figures, which statement is true regarding zeroes at the beginning of a number?
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When performing addition or subtraction with significant figures, how should the final result be rounded?
When performing addition or subtraction with significant figures, how should the final result be rounded?
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Which of the following best describes accuracy in measurements?
Which of the following best describes accuracy in measurements?
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How should significant figures be handled when multiplying two measured values?
How should significant figures be handled when multiplying two measured values?
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If a mass is measured as 2.2405 g with an uncertainty of ±0.0001 g, how many significant figures are present?
If a mass is measured as 2.2405 g with an uncertainty of ±0.0001 g, how many significant figures are present?
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Which two types of errors can affect the accuracy of measurements?
Which two types of errors can affect the accuracy of measurements?
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Which of the following statements about significant figures is incorrect?
Which of the following statements about significant figures is incorrect?
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What is the base unit for mass in the metric system?
What is the base unit for mass in the metric system?
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Which of the following prefixes represents a factor of $10^{12}$?
Which of the following prefixes represents a factor of $10^{12}$?
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What is the equivalent of 1 milliwatt (mW) in watts?
What is the equivalent of 1 milliwatt (mW) in watts?
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Which metric system prefix denotes a factor of $10^{6}$?
Which metric system prefix denotes a factor of $10^{6}$?
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What unit of temperature is not part of the metric system?
What unit of temperature is not part of the metric system?
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Which prefix is used to denote a factor of $10^{-2}$?
Which prefix is used to denote a factor of $10^{-2}$?
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The unit for measuring the amount of a substance in the metric system is called?
The unit for measuring the amount of a substance in the metric system is called?
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What is the meaning of the prefix Giga (G) in the metric system?
What is the meaning of the prefix Giga (G) in the metric system?
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Which of the following represents units of volume in the metric system?
Which of the following represents units of volume in the metric system?
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What prefix corresponds to a factor of $10^{15}$?
What prefix corresponds to a factor of $10^{15}$?
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Study Notes
Chemistry: The Central Science - Chapter 1
- Chemistry is the study of matter, its properties, and the changes it undergoes.
- Chemistry underpins the fundamental understanding of many science-related fields.
- Matter is anything that has mass and takes up space.
Classifications of Matter
- Matter exists in three states: solid, liquid, and gas.
- Matter can be classified by its composition: elements or compounds.
- Elements consist of only one type of atom.
- Compounds contain two or more different types of atoms bonded together.
- Mixtures can vary in composition throughout a sample (heterogeneous) or have the same composition throughout the sample (homogeneous).
- A homogeneous mixture is also called a solution.
Representing Elements
- Chemists use symbols to represent elements.
- Symbols are typically one or two letters; the first is always capitalized.
- Some element symbols are derived from Latin or Greek names.
Elements and Composition
- There are currently 118 named elements.
- The five primary elements that comprise 90% of the Earth's crust by mass are: Aluminum, Iron, Calcium, Silicon, and Oxygen.
- Three elements make up 90% of the human body by mass; Oxygen, Carbon, and Hydrogen.
- Oxygen plays a crucial role in both the Earth's crust and the human body.
Compounds and Composition
- Compounds have a definite composition.
- The relative number of atoms of each element in a compound remains consistent in any sample (Law of Constant Composition).
Mixtures
- Mixtures exhibit the properties of their constituent substances.
- Mixtures can have varying compositions (heterogeneous) or uniform composition throughout the sample (homogeneous).
- Homogenous mixtures are also called solutions.
- Mixtures can be separated based on physical properties—methods like filtration, distillation, and chromatography.
Making a Decision (Classifying Matter)
- The flowchart on page 11 outlines a structured method for classifying matter as homogenous mixtures, heterogeneous mixtures, elements, or compounds.
Properties of Matter
- Properties are characteristics of a substance.
- Physical properties can be observed without changing the substance's identity (e.g., color, odor, density, melting point, boiling point, and hardness).
- Chemical properties describe how a substance reacts to form a new substance (e.g., flammability, ability to rust, oxidation).
- Intensive properties are independent of the amount of substance (e.g., density, boiling point).
- Extensive properties depend on the amount of substance (e.g., mass, volume).
Physical and Chemical Changes
- Physical changes alter a substance's physical properties but do not change its composition (e.g., changes of state, temperature, or volume).
- Chemical changes produce new substances with different properties (e.g., combustion, oxidation, and decomposition).
Separating Mixtures
- Mixtures can be separated using techniques based on physical properties of the components.
- Examples include filtration, distillation, and chromatography.
Energy
- Energy is the capacity to do work or transfer heat.
- Work is energy transferred when a force causes an object's displacement.
- Heat is the energy used to change an object's temperature.
- Force is a push or pull on an object.
Two Fundamental Forms of Energy
- Kinetic energy is the energy of motion and depends on an object's mass and velocity.
- Potential energy is stored energy based on an object's position relative to other objects.
Units of Measurement
- Numbers are critical in chemistry, with many topics being quantitative.
- Units of measurement are essential in science.
- Quantities are measured and calculated using units.
- Uncertainty exists in measurements. Significant figures indicate the precision of a measurement and are used in calculations.
- Dimensional analysis converts values from one unit to another using conversion factors.
Units of Measurement-SI Units
- SI units are a standard system of measurement.
- Different base units exist for each measurable quantity.
Units of Measurement-Metric System
- The metric system uses base metric units for quantities like mass, length, time, temperature, amount of substance, volume.
- Prefixes are used to adjust base units to convenient sizes for common usage (e.g., liters).
Significant Figures
- All digits in a measured value are significant, including the uncertain ones.
- Significant figures are essential to avoid overstating the accuracy of answers in calculations.
- When performing calculations, follow rules regarding significant figures in addition/subtraction and multiplication/division.
- Measurement has uncertainty. The last reported digit is reliable, but not perfectly accurate.
Significant Figures Rules
- Non-zero digits are significant.
- Zeros between non-zero digits are significant.
- Leading zeros are not significant.
- Trailing zeros are significant if a decimal point is present.
Significant Figures in Calculations
- The least precise measurement affects the precision of the answer.
- Results from addition/subtraction to the decimal place of the least precise measurement.
- Results from multiplication/division with the same number of significant figures as the least precise measurement.
Dimensional Analysis
- Dimensional analysis uses conversion factors based on equalities to change units in calculations.
- These factors are set up as ratios, allowing units to cancel out leaving the desired unit.
- Multiple conversions are possible, but each conversion must be an equality.
Density
- Density is the mass per unit volume of a substance (mass ÷ volume).
- Common units include grams per milliliter (g/mL) and grams per cubic centimeter (g/cm³).
Energy Units
- The Joule (J) is the SI unit of energy that describes the power of a substance (rate of energy consumption or production).
- Other energy units exist and were historically used (e.g., Calories).
Uncertainty in Measurements
- Measuring devices have varying degrees of accuracy.
- Measured numbers always have uncertainty.
- The last reported digit is an estimate, and not exact.
Numbers Encountered in Science
- Exact numbers arise from counting or definitions.
- Inexact (measured) numbers have inherent uncertainty due to limitations of instruments & measuring techniques (e.g., human error).
- Uncertainties exist in measured numbers.
Precision Versus Accuracy
- Precision is how closely measurements agree with each other.
- Accuracy is how closely measurements agree with the true value.
- Standard deviation is often used in experiments to assess accuracy and precision
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Description
Test your knowledge of fundamental chemistry concepts, including elements, properties of matter, and mixtures. This quiz covers essential topics like the Law of Constant Composition and distinguishes between physical and chemical changes. Perfect for students in introductory chemistry courses.
