CHEM 111 - Exam one
Atoms vs. Molecules
Q: What is an atom?
A: The smallest particle of an element that retains its properties.
Q: What is a molecule?
A: Two or more atoms joined together. Example: N₂, H₂O, NaCl.
Classification of Matter
Q: What is a pure substance?
A: A substance composed of a single type of particle with a fixed composition.
Q: What are the two types of pure substances?
A: Elements (cannot be broken down) and compounds (two or more elements in fixed proportions).
Q: What is a mixture?
A: A combination of two or more substances that can be physically separated.
Q: What are the two types of mixtures?
A:
Homogeneous (solution): Uniform throughout (e.g., wine).
Heterogeneous: Different composition in different regions (e.g., beef stew).
Physical vs. Chemical Properties
Q: What are physical properties?
A: Properties that can be observed without changing the substance (e.g., boiling point, density).
Q: What are chemical properties?
A: Properties that involve changing the chemical composition (e.g., iron rusting).
Q: Classify the following properties as physical or chemical:
Boiling point of ethyl alcohol? Physical
Argon is an inert gas? Chemical
Tendency of iron to rust? Chemical
Gold is yellow? Physical
Physical vs. Chemical Changes
Q: What is a physical change?
A: A change in form but not composition (e.g., ice melting).
Q: What is a chemical change?
A: A change that alters the chemical composition (e.g., burning sugar).
Q: Classify the following changes as physical or chemical:
Sugar burning? Chemical
Sugar dissolving in water? Physical
Platinum ring dulling? Physical
Silver tarnishing? Chemical
Intensive vs. Extensive Properties
Q: What is an intensive property?
A: A property independent of amount (e.g., density, boiling point).
Q: What is an extensive property?
A: A property dependent on the amount (e.g., mass, volume).
Q: Classify the following properties:
Density of iron (7.86 g/mL)? Intensive
15.0 mL of ethanol? Extensive
Boiling point of water (100°C)? Intensive
36.45 g of NaCl? Extensive
Measurements & Units
Q: What are the standard SI units?
A: Length (m), mass (g, kg), time (s), temperature (°C, K).
Q: What is the formula for density?
A: Density = mass/volume (g/mL).
Q: What are examples of exact numbers?
A: Counted objects (10 hats) or defined relationships (1 ft = 12 in).
Q: What are five common conversion factors?
A: 1 L = 1000 mL, 1 kg = 1000 g, 1 in = 2.54 cm, 1 mile = 1.609 km, 1 lb = 453.6 g.
Dalton’s Atomic Theory & Laws
Q: What are the key points of Dalton’s atomic theory?
A:
Elements are composed of atoms.
Atoms of one element are identical but differ from other elements.
Atoms combine in whole number ratios.
Atoms cannot be created or destroyed in a chemical reaction.
Q: What is the Law of Definite Proportions?
A: A compound always has the same proportion of elements.
Q: What is the Law of Multiple Proportions?
A: Different compounds with the same elements exist in different whole-number ratios.
Nuclear Theory & Subatomic Particles
Q: What are the three subatomic particles?
A: Proton (+ charge), Neutron (neutral), Electron (- charge).
Q: Which Rutherford nuclear theory statements are false?
A:
Volume of hydrogen is due to proton? False; most of the volume is empty space.
Fluorine’s mass comes from electrons? False; mass is mostly from protons and neutrons.
Q: Identify true or false statements about subatomic particles:
Protons and electrons have opposite charges? True
Protons and neutrons have similar mass? True
Some atoms have no protons? False
Neutrons have opposite charge to protons? False (they are neutral).
Isotopes & Ions
Q: What is an isotope?
A: Atoms of the same element with different numbers of neutrons.
Q: Write the nuclear symbols:
Copper with 34 neutrons? ⁶³₂₉Cu
Potassium with 21 neutrons? ⁴⁰₁₉K
Q: Determine protons, neutrons, and electrons:
⁴⁰₁₉K → 19 p+, 21 n, 19 e-
²²⁶₈₈Ra → 88 p+, 138 n, 88 e-
Q: Determine protons and electrons in ions:
Al³⁺ → 13 p+, 10 e-
Se²⁻ → 34 p+, 36 e-
Classification of Matter
Q: What is a pure substance?
A: A substance composed of a single type of particle with a fixed composition.
Q: What are the two types of pure substances?
A: Elements (cannot be broken down) and compounds (two or more elements in fixed proportions).
Q: What is a mixture?
A: A combination of two or more substances that can be physically separated.
Q: What are the two types of mixtures?
A:
Homogeneous (solution): Uniform throughout (e.g., wine).
Heterogeneous: Different composition in different regions (e.g., beef stew).
Physical vs. Chemical Properties
Q: What are physical properties?
A: Properties that can be observed without changing the substance (e.g., boiling point, density).
Q: What are chemical properties?
A: Properties that involve changing the chemical composition (e.g., iron rusting).
Q: Classify the following properties as physical or chemical:
Boiling point of ethyl alcohol? Physical
Argon is an inert gas? Chemical
Tendency of iron to rust? Chemical
Gold is yellow? Physical
Physical vs. Chemical Changes
Q: What is a physical change?
A: A change in form but not composition (e.g., ice melting).
Q: What is a chemical change?
A: A change that alters the chemical composition (e.g., burning sugar).
Q: Classify the following changes as physical or chemical:
Sugar burning? Chemical
Sugar dissolving in water? Physical
Platinum ring dulling? Physical
Silver tarnishing? Chemical
Intensive vs. Extensive Properties
Q: What is an intensive property?
A: A property independent of amount (e.g., density, boiling point).
Q: What is an extensive property?
A: A property dependent on the amount (e.g., mass, volume).
Q: Classify the following properties:
Density of iron (7.86 g/mL)? Intensive
15.0 mL of ethanol? Extensive
Boiling point of water (100°C)? Intensive
36.45 g of NaCl? Extensive
Measurements & Units
Q: What are the standard SI units?
A: Length (m), mass (g, kg), time (s), temperature (°C, K).
Q: What is the formula for density?
A: Density = mass/volume (g/mL).
Q: What are examples of exact numbers?
A: Counted objects (10 hats) or defined relationships (1 ft = 12 in).
Q: What are five common conversion factors?
A: 1 L = 1000 mL, 1 kg = 1000 g, 1 in = 2.54 cm, 1 mile = 1.609 km, 1 lb = 453.6 g.
Dalton’s Atomic Theory & Laws
Q: What are the key points of Dalton’s atomic theory?
A:
Elements are composed of atoms.
Atoms of one element are identical but differ from other elements.
Atoms combine in whole number ratios.
Atoms cannot be created or destroyed in a chemical reaction.
Q: What is the Law of Definite Proportions?
A: A compound always has the same proportion of elements.
Q: What is the Law of Multiple Proportions?
A: Different compounds with the same elements exist in different whole-number ratios.
Nuclear Theory & Subatomic Particles
Q: What are the three subatomic particles?
A: Proton (+ charge), Neutron (neutral), Electron (- charge).
Q: Which Rutherford nuclear theory statements are false?
A:
Volume of hydrogen is due to proton? False; most of the volume is empty space.
Fluorine’s mass comes from electrons? False; mass is mostly from protons and neutrons.
Q: Identify true or false statements about subatomic particles:
Protons and electrons have opposite charges? True
Protons and neutrons have similar mass? True
Some atoms have no protons? False
Neutrons have opposite charge to protons? False (they are neutral).