Chemistry Chapter 1: The Central Science

Podcast

Play an AI-generated podcast conversation about this lesson

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?

Cannot be separated into simpler substances by chemical means Signup and view all the answers

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

Changes in the arrangement of atoms and molecules Signup and view all the answers

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

It melts into a liquid. Signup and view all the answers

Which temperature scale is considered the absolute scale?

Kelvin Signup and view all the answers

What is the equivalent of 28°C in Kelvin?

298 K Signup and view all the answers

Which of the following describes the relationship for calculating density?

Mass divided by volume. Signup and view all the answers

How is 1 liter defined in terms of volume?

Equal to a cubic decimeter. Signup and view all the answers

Which of the following substances is classified as a compound?

Baking soda Signup and view all the answers

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

Homogeneous Signup and view all the answers

Which statement is true about mixtures?

Their components retain distinct identities. Signup and view all the answers

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

Particles assume the shape of their container. Signup and view all the answers

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

Distinct identities of components Signup and view all the answers

What classification does aluminum foil belong to?

Substance, element Signup and view all the answers

Which of the following examples represents a heterogeneous mixture?

Sugar mixed with iron filings Signup and view all the answers

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

Particles are held together closely in an orderly fashion. Signup and view all the answers

How many significant figures are in the measurement 250 mL?

2 Signup and view all the answers

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

The number with the least digits to the right of the decimal point. Signup and view all the answers

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

11 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?

7.5 g, unlimited significant figures. Signup and view all the answers

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

Round down. Signup and view all the answers

What distinguishes a chemical property from a physical property?

Chemical properties require changes in identity of a substance. Signup and view all the answers

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

Ice melting into water. Signup and view all the answers

What is an extensive property?

A property that reflects the size of an object. Signup and view all the answers

Which of the following statements about significant figures is true?

Zeros between non-zero digits are always significant. Signup and view all the answers

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

A measured length using a ruler. Signup and view all the answers

How many significant figures are in the number 0.004560?

4 Signup and view all the answers

What happens to a substance after a chemical change?

The original substance no longer exists in its initial form. Signup and view all the answers

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

Temperature. Signup and view all the answers

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

116.2 L Signup and view all the answers

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

The reproducibility of measurements Signup and view all the answers

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

The measurements are close to the true value and close to each other. Signup and view all the answers

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

Conversion factor Signup and view all the answers

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

0.333 g Signup and view all the answers

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

Student B Signup and view all the answers

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

To change one measure to another 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?

32.44 cm³ Signup and view all the answers

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 H₂O.
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.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

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.