CHEM 1411 – GENERAL CHEMISTRY I VERIFIED ANSWERS
AND QUESTIONS - MOST RECENT EDITION 2026
1. What is chemistry?
ANSWER : Chemistry is the scientific study of matter, its properties,
composition, structure, and the changes it undergoes.
2. Define matter.
ANSWER : Matter is anything that has mass and occupies space.
3. What are the three states of matter?
ANSWER : The three states of matter are solid, liquid, and gas (plasma is
sometimes considered a fourth).
4. Distinguish between a physical property and a chemical property.
ANSWER : A physical property can be observed without changing the
substance's chemical composition (e.g., color, density). A chemical property
describes the ability of a substance to undergo a chemical change (e.g.,
flammability, reactivity).
5. What is a physical change?
ANSWER : A physical change alters the form or appearance of matter but does
not change its chemical composition (e.g., melting ice, cutting wood).
6. What is a chemical change?
ANSWER : A chemical change produces one or more new substances with
different chemical compositions (e.g., burning wood, rusting iron).
7. Define element.
ANSWER : An element is a pure substance that cannot be broken down into
simpler substances by ordinary chemical means.
8. Define compound.
ANSWER : A compound is a pure substance composed of two or more elements
chemically combined in definite proportions.
9. What is a mixture?
, ANSWER : A mixture is a combination of two or more substances that are not
chemically combined and can be separated by physical means.
10. Distinguish between homogeneous and heterogeneous mixtures.
ANSWER : A homogeneous mixture (solution) has a uniform composition
throughout. A heterogeneous mixture does not have a uniform composition (e.g.,
sand in water).
11. What are the SI base units for length, mass, and time?
ANSWER : Meter (m) for length, kilogram (kg) for mass, and second (s) for time.
12. What is the SI unit for temperature?
ANSWER : Kelvin (K).
13. Convert 25°C to Kelvin.
ANSWER : K = °C + 273.15, so 25 + 273.15 = 298.15 K.
14. What is significant figures?
ANSWER : Significant figures are the digits in a measurement that are known
with certainty plus one estimated digit. They indicate the precision of a
measurement.
15. How many significant figures are in 0.00450?
ANSWER : Three significant figures (4, 5, and 0). Leading zeros are not
significant; the trailing zero after 5 is significant.
16. What is accuracy vs. precision?
ANSWER : Accuracy refers to how close a measurement is to the true value.
Precision refers to how close repeated measurements are to each other.
17. Define density.
ANSWER : Density is the mass per unit volume of a substance: d = m/V.
Common units are g/mL or g/cm³.
18. A sample has a mass of 45.0 g and a volume of 15.0 mL. What is its
density?
ANSWER : d = m/V = 45.0 g / 15.0 mL = 3.00 g/mL.
19. What is dimensional analysis (factor-label method)?
ANSWER : Dimensional analysis is a problem-solving technique that uses
conversion factors (fractions equal to 1) to convert between units.
20. Convert 5.00 km to meters.
ANSWER : 5.00 km × (1000 m / 1 km) = 5000 m = 5.00 × 10³ m.
UNIT 2: Atoms, Molecules, and Ions
, 21. State Dalton's Atomic Theory.
ANSWER : Dalton's theory states: (1) Matter is composed of atoms. (2) All
atoms of an element are identical. (3) Atoms of different elements are different.
(4) Atoms combine in whole-number ratios to form compounds. (5) Atoms are
rearranged, not created or destroyed, in chemical reactions.
22. What is the Law of Conservation of Mass?
ANSWER : Matter cannot be created or destroyed in a chemical reaction; the
total mass of reactants equals the total mass of products.
23. What is the Law of Definite Proportions?
ANSWER : A compound always contains the same elements in the same mass
ratio regardless of where the sample came from.
24. What subatomic particles make up an atom and where are they located?
ANSWER : Protons (positive, in nucleus), neutrons (neutral, in nucleus), and
electrons (negative, in electron cloud surrounding the nucleus).
25. What is the atomic number?
ANSWER : The atomic number (Z) is the number of protons in the nucleus of an
atom and identifies the element.
26. What is the mass number?
ANSWER : The mass number (A) is the total number of protons plus neutrons in
the nucleus of an atom.
27. Define isotopes.
ANSWER : Isotopes are atoms of the same element (same number of protons)
that have different numbers of neutrons, giving them different mass numbers.
28. What is atomic mass?
ANSWER : Atomic mass is the weighted average mass of all naturally occurring
isotopes of an element, expressed in atomic mass units (amu).
29. How many protons, neutrons, and electrons are in ¹⁴C?
ANSWER : Carbon-14: 6 protons, 8 neutrons (14 − 6), and 6 electrons (neutral
atom).
30. What is a cation? An anion?
ANSWER : A cation is a positively charged ion (lost electrons). An anion is a
negatively charged ion (gained electrons).
31. What is the periodic table?
AND QUESTIONS - MOST RECENT EDITION 2026
1. What is chemistry?
ANSWER : Chemistry is the scientific study of matter, its properties,
composition, structure, and the changes it undergoes.
2. Define matter.
ANSWER : Matter is anything that has mass and occupies space.
3. What are the three states of matter?
ANSWER : The three states of matter are solid, liquid, and gas (plasma is
sometimes considered a fourth).
4. Distinguish between a physical property and a chemical property.
ANSWER : A physical property can be observed without changing the
substance's chemical composition (e.g., color, density). A chemical property
describes the ability of a substance to undergo a chemical change (e.g.,
flammability, reactivity).
5. What is a physical change?
ANSWER : A physical change alters the form or appearance of matter but does
not change its chemical composition (e.g., melting ice, cutting wood).
6. What is a chemical change?
ANSWER : A chemical change produces one or more new substances with
different chemical compositions (e.g., burning wood, rusting iron).
7. Define element.
ANSWER : An element is a pure substance that cannot be broken down into
simpler substances by ordinary chemical means.
8. Define compound.
ANSWER : A compound is a pure substance composed of two or more elements
chemically combined in definite proportions.
9. What is a mixture?
, ANSWER : A mixture is a combination of two or more substances that are not
chemically combined and can be separated by physical means.
10. Distinguish between homogeneous and heterogeneous mixtures.
ANSWER : A homogeneous mixture (solution) has a uniform composition
throughout. A heterogeneous mixture does not have a uniform composition (e.g.,
sand in water).
11. What are the SI base units for length, mass, and time?
ANSWER : Meter (m) for length, kilogram (kg) for mass, and second (s) for time.
12. What is the SI unit for temperature?
ANSWER : Kelvin (K).
13. Convert 25°C to Kelvin.
ANSWER : K = °C + 273.15, so 25 + 273.15 = 298.15 K.
14. What is significant figures?
ANSWER : Significant figures are the digits in a measurement that are known
with certainty plus one estimated digit. They indicate the precision of a
measurement.
15. How many significant figures are in 0.00450?
ANSWER : Three significant figures (4, 5, and 0). Leading zeros are not
significant; the trailing zero after 5 is significant.
16. What is accuracy vs. precision?
ANSWER : Accuracy refers to how close a measurement is to the true value.
Precision refers to how close repeated measurements are to each other.
17. Define density.
ANSWER : Density is the mass per unit volume of a substance: d = m/V.
Common units are g/mL or g/cm³.
18. A sample has a mass of 45.0 g and a volume of 15.0 mL. What is its
density?
ANSWER : d = m/V = 45.0 g / 15.0 mL = 3.00 g/mL.
19. What is dimensional analysis (factor-label method)?
ANSWER : Dimensional analysis is a problem-solving technique that uses
conversion factors (fractions equal to 1) to convert between units.
20. Convert 5.00 km to meters.
ANSWER : 5.00 km × (1000 m / 1 km) = 5000 m = 5.00 × 10³ m.
UNIT 2: Atoms, Molecules, and Ions
, 21. State Dalton's Atomic Theory.
ANSWER : Dalton's theory states: (1) Matter is composed of atoms. (2) All
atoms of an element are identical. (3) Atoms of different elements are different.
(4) Atoms combine in whole-number ratios to form compounds. (5) Atoms are
rearranged, not created or destroyed, in chemical reactions.
22. What is the Law of Conservation of Mass?
ANSWER : Matter cannot be created or destroyed in a chemical reaction; the
total mass of reactants equals the total mass of products.
23. What is the Law of Definite Proportions?
ANSWER : A compound always contains the same elements in the same mass
ratio regardless of where the sample came from.
24. What subatomic particles make up an atom and where are they located?
ANSWER : Protons (positive, in nucleus), neutrons (neutral, in nucleus), and
electrons (negative, in electron cloud surrounding the nucleus).
25. What is the atomic number?
ANSWER : The atomic number (Z) is the number of protons in the nucleus of an
atom and identifies the element.
26. What is the mass number?
ANSWER : The mass number (A) is the total number of protons plus neutrons in
the nucleus of an atom.
27. Define isotopes.
ANSWER : Isotopes are atoms of the same element (same number of protons)
that have different numbers of neutrons, giving them different mass numbers.
28. What is atomic mass?
ANSWER : Atomic mass is the weighted average mass of all naturally occurring
isotopes of an element, expressed in atomic mass units (amu).
29. How many protons, neutrons, and electrons are in ¹⁴C?
ANSWER : Carbon-14: 6 protons, 8 neutrons (14 − 6), and 6 electrons (neutral
atom).
30. What is a cation? An anion?
ANSWER : A cation is a positively charged ion (lost electrons). An anion is a
negatively charged ion (gained electrons).
31. What is the periodic table?
