Chemistry Basics and Measurements

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Questions and Answers

Which of the following correctly defines chemistry?

The study of living organisms.

The study of celestial bodies and their movements.

The study of matter and its interactions. (correct)

The study of human behavior and mental processes.

Which of the following is a characteristic feature of a homogeneous mixture?

It has a uniform composition throughout. (correct)

It contains multiple phases of matter.

The components are easily distinguishable.

It can be separated by physical means.

What is the Kelvin equivalent of 25 degrees Celsius?

32 K

300 K

273 K

298 K (correct)

What does the atomic number of an element represent?

The total number of protons in the nucleus. Signup and view all the answers

How do you calculate the mass number of an atom?

By adding the number of protons to the number of neutrons. Signup and view all the answers

Which of the following best describes an isotope?

Atoms that are chemically identical but have different mass numbers. Signup and view all the answers

What is the relationship between atomic mass unit (amu) and grams?

1 amu is equivalent to 1/12 of the mass of a carbon-12 atom. Signup and view all the answers

Which of the following represents a cation?

A sodium ion ($Na^+$). Signup and view all the answers

What is the likely charge of an ion formed by an element in group 1 of the periodic table?

1 Signup and view all the answers

Which of the following best describes the difference between ionic and molecular compounds?

Ionic compounds consist of charged ions held together by electrostatic forces, while molecular compounds consist of molecules formed by covalent bonds. Signup and view all the answers

Which of the following statements accurately defines Avogadro's number?

6.0221 Signup and view all the answers

How can the empirical formula of a compound be determined from percent composition?

By converting the percent composition to moles and simplifying the ratios. Signup and view all the answers

What is the main difference between molar mass and molecular weight?

Molecular weight is a unitless quantity while molar mass has units of g/mol. Signup and view all the answers

Study Notes

Chemistry Definition

Chemistry studies the composition, structure, properties, and reactions of matter

Matter & Non-Matter

Matter has mass and takes up space
Non-matter lacks mass and does not occupy space

SI Units of Measurement

Length: meter (m)
Mass: kilogram (kg)
Time: second (s)
Temperature: Kelvin (K)
Amount of substance: mole (mol)
Electric current: ampere (A)
Luminous intensity: candela (cd)

SI/Metric Unit Prefixes

Kilo (k): 1000
Hecto (h): 100
Deka (da): 10
Deci (d): 0.1
Centi (c): 0.01
Milli (m): 0.001
Micro (µ): 0.000001
Nano (n): 0.000000001

Scientific Notation

Expressing very large or very small numbers using powers of 10

Density & Calculations

Density: mass per unit volume
Formula: Density = Mass/Volume

Dimensional Analysis

Converting between different units using conversion factors

Temperature Conversions

Celsius to Fahrenheit: °F = (°C × 9/5) + 32
Fahrenheit to Celsius: °C = (°F - 32) × 5/9
Kelvin to Celsius: K = °C + 273.15
Celsius to Kelvin: °C = K - 273.15

Matter Classifications

Pure substances: elements and compounds
Mixtures: homogeneous and heterogeneous

Homogeneous vs. Heterogeneous Mixtures

Homogeneous: uniform composition
Heterogeneous: non-uniform composition

States of Matter

Solid: fixed shape and volume
Liquid: fixed volume, but takes the shape of its container
Gas: no fixed shape or volume, expands to fill its container

Phase Changes

Solid to liquid: melting
Liquid to solid: freezing
Liquid to gas: vaporization
Gas to liquid: condensation
Solid to gas: sublimation
Gas to solid: deposition

Physical and Chemical Changes

Physical change: alters the form or appearance of a substance, but not its chemical composition
Chemical change: results in the formation of new substances with different chemical properties

Physical and Chemical Properties

Physical property: can be observed without changing the substance's composition
Chemical property: describes how a substance reacts with other substances

Atomic Structure

Composed of protons, neutrons, and electrons
Protons: positive charge, located in the nucleus
Neutrons: no charge, located in the nucleus
Electrons: negative charge, located in the electron cloud surrounding the nucleus

Atomic Number

Number of protons in an atom's nucleus, defining the element

Chemical Symbols

One or two letters representing an element

Isotopes

Atoms of the same element with different numbers of neutrons
Same atomic number, but different mass numbers

Average Atomic Mass

Weighted average of the masses of all naturally occurring isotopes of an element

Ions

Atoms that have gained or lost electrons
Cations: positively charged ions
Anions: negatively charged ions

Polyatomic Ions

Groups of atoms with an overall charge

Ionic Compounds

Formed by the electrostatic attraction between oppositely charged ions

Molecular Compounds

Formed by the sharing of electrons between atoms

Mole & Avogadro's Number

Mole: a unit of amount of substance
Avogadro's number: 6.022 × 10^23 particles per mole

Atomic Weight, Molecular Weight, & Molar Mass

Atomic weight: mass of one atom of an element
Molecular weight: mass of one molecule of a compound
Molar mass: mass of one mole of a substance

Percent Composition

Percentage by mass of each element in a compound

Empirical & Molecular Formulas

Empirical formula: simplest whole-number ratio of atoms in a compound
Molecular formula: actual number of atoms of each element in a molecule

Finding Empirical & Molecular Formulas

Empirical formula from percent composition: convert percentage to mass, then to moles, and find the simplest whole-number ratio of moles
Molecular formula from empirical formula: calculate the molar mass of the empirical formula, and divide the molar mass of the compound by the molar mass of the empirical formula to determine the multiplier for the empirical formula

Practice Problems

Chapter 1 (Page 50): 9, 11, 13, 19, 25, 29, 39, 45, 57, 65, 67, 75, 81, 87, 89, 93, 95, 97
Chapter 2 (Page 107): 7, 19, 25, 29, 33, 39, 41, 47
Chapter 3 (Page 151): 1, 5, 9, 13, 17, 19, 25, 27, 31, 39, 43

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Description

Test your knowledge on fundamental chemistry concepts including matter, SI units, and density calculations. This quiz will also cover scientific notation and temperature conversions, helping you solidify your understanding of essential measurement principles in chemistry.