CHEM 121 STUDY GUIDE EXAM 1
UPDATED EXAM WITH CORRECT
QUESTIONS AND ANSWERS 2025
Hypothesis vs Theory vs Law - CORRECT-ANSWERSHypothesis: If, then, because
Law: Statement or equation about a relationship
- ex: force = mass * gravity
Theory: Explains why a law exists
Law of Conservation of Mass - CORRECT-ANSWERSMass is always constant
- Reactant mass = Product mass
They are used (upheld) in chemical equations
Three common states of matter and their characteristics - CORRECT-ANSWERS- Solid
(s): color
- Liquid (aq): melting point, solubility
- Gas (g):
Difference between Elements, Compounds, Homogeneous and Heterogeneous mixtures
- CORRECT-ANSWERS- Substances: CANNOT be separated by physical process
- Mixture: CAN be separated by physical process
- Elements: CANNOT be decomposed by chemicals
- Compounds: 2 or more elements combined
, - Homogeneous: ex: salt water
- Heterogeneous: physically distinct parts (ex: sand)
Difference between Physical and Chemical changes / their processes - CORRECT-
ANSWERSPhysical change: boiling, melting, change of states of matter (solid -> liquid -
> gas)
Chemical change: combustion, photosynthesis, rusting
physical vs chemical properties - CORRECT-ANSWERSPhysical: color, melting point,
solubility, boiling point
Chemical: creativity in acid, ability to rust (react with oxygen)
Precision vs Accuracy - CORRECT-ANSWERSPrecision: closeness to "set of values
obtained" (sample mean)
Accuracy: closeness to true value (population mean)
Sig Figs - CORRECT-ANSWERS2500 = 2 sig figs
2500.0 = 5 sig figs
0.0077 = 2 sig figs
0.03400 = 4 sig figs
Kilogram vs Gram
Millogram vs Gram
Nanogram vs Gram - CORRECT-ANSWERS1000g = 1kg
1000mg = 1g
UPDATED EXAM WITH CORRECT
QUESTIONS AND ANSWERS 2025
Hypothesis vs Theory vs Law - CORRECT-ANSWERSHypothesis: If, then, because
Law: Statement or equation about a relationship
- ex: force = mass * gravity
Theory: Explains why a law exists
Law of Conservation of Mass - CORRECT-ANSWERSMass is always constant
- Reactant mass = Product mass
They are used (upheld) in chemical equations
Three common states of matter and their characteristics - CORRECT-ANSWERS- Solid
(s): color
- Liquid (aq): melting point, solubility
- Gas (g):
Difference between Elements, Compounds, Homogeneous and Heterogeneous mixtures
- CORRECT-ANSWERS- Substances: CANNOT be separated by physical process
- Mixture: CAN be separated by physical process
- Elements: CANNOT be decomposed by chemicals
- Compounds: 2 or more elements combined
, - Homogeneous: ex: salt water
- Heterogeneous: physically distinct parts (ex: sand)
Difference between Physical and Chemical changes / their processes - CORRECT-
ANSWERSPhysical change: boiling, melting, change of states of matter (solid -> liquid -
> gas)
Chemical change: combustion, photosynthesis, rusting
physical vs chemical properties - CORRECT-ANSWERSPhysical: color, melting point,
solubility, boiling point
Chemical: creativity in acid, ability to rust (react with oxygen)
Precision vs Accuracy - CORRECT-ANSWERSPrecision: closeness to "set of values
obtained" (sample mean)
Accuracy: closeness to true value (population mean)
Sig Figs - CORRECT-ANSWERS2500 = 2 sig figs
2500.0 = 5 sig figs
0.0077 = 2 sig figs
0.03400 = 4 sig figs
Kilogram vs Gram
Millogram vs Gram
Nanogram vs Gram - CORRECT-ANSWERS1000g = 1kg
1000mg = 1g
