Introduction to Chemistry: Test Preparation Study Guide

Test Preparation Topics for Introduction to Chemistry

Scientific Notation

Scientific notation is a method used to express very large or very small numbers in a compact form. It is commonly used in chemistry to simplify calculations and represent measurements.

• Definition: A number is written as the product of a coefficient (between 1 and 10) and a power of ten.

• Example: $6,500 = 6.5 \times 10^3$

• Conversion: Move the decimal point to create a coefficient between 1 and 10, then count the number of places moved to determine the exponent.

• Reverse Conversion: To convert from scientific notation to decimal, multiply the coefficient by $10^n$.

Significant Figures

Significant figures (sig figs) indicate the precision of a measured or calculated quantity. The rules for determining significant figures are essential for reporting results correctly in chemistry.

• Rules for Zeros:

  • Leading zeros are not significant.

  • Captive (middle) zeros are always significant.

  • Trailing zeros are significant only if there is a decimal point.

• Calculations:

  • Adding/Subtracting: The result should have the same number of decimal places as the measurement with the fewest decimal places.

  • Multiplying/Dividing: The result should have the same number of significant figures as the measurement with the fewest significant figures.

• Example: $2.50 \times 3.1 = 7.8$ (rounded to 2 sig figs)

Metric Prefixes

Metric prefixes are used to indicate multiples or fractions of base units in the metric system. Knowing common prefixes is important for unit conversions.

• Reference: Table 2.2 on page 30 (important prefixes such as kilo-, centi-, milli-, etc.)

• Example: $1 \text{ kilometer} = 1,000 \text{ meters}$

Metric to Metric Conversions

Converting between metric units involves multiplying or dividing by powers of ten, based on the prefixes.

• Example: $1 \text{ cm} = 0.01 \text{ m}$

• Method: Use conversion factors based on metric prefixes.

English to Metric Conversions

Converting between English and metric units is a common task in chemistry, especially for measurements.

• Common Conversions:

  • $1 \text{ inch} = 2.54 \text{ cm}$

  • $12 \text{ inches} = 1 \text{ foot}$

  • $1 \text{ yard} = 3 \text{ feet}$

Density Calculations

Density is a physical property defined as mass per unit volume. The density triangle helps solve for density, mass, or volume.

• Formula: $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

• Triangle Method: Cover the variable you want to solve for; the remaining arrangement gives the formula.

• Example: If mass = 10 g and volume = 2 mL, $\text{Density} = \frac{10}{2} = 5 \text{ g/mL}$

Volume by Displacement

Volume by displacement is a technique used to measure the volume of irregularly shaped objects by observing the change in water level.

• Method: Submerge the object in water and measure the increase in volume.

• Example: Initial water = 50 mL, final water = 55 mL, object volume = 5 mL

Key Terms and SI Base Units

Understanding key terms and SI base units is fundamental for all chemistry calculations and measurements.

• Reference: Table 2.1 on page 29 (important SI base units)

• Common SI Units:

  • Length: meter (m)

  • Mass: kilogram (kg)

  • Time: second (s)

  • Temperature: kelvin (K)

  • Amount of substance: mole (mol)

Rounding Numbers

Rounding numbers is necessary to report results with the correct number of significant figures.

• Rule: If the digit to be dropped is less than 5, leave the preceding digit unchanged; if 5 or greater, increase the preceding digit by one.

• Example: 2.678 rounded to two decimal places is 2.68

Test Format and Policies

Understanding the test format and policies helps you prepare effectively and avoid common mistakes.

• Test Format: 22 true/false questions and 38 multiple choice questions

• Calculator Policy: Calculators are required; borrowing or sharing is not allowed.

• Test Passes: Eligibility for test question passes requires taking the test at the scheduled date and time.

Summary Table: Common Metric Prefixes

Prefix	Symbol	Factor
kilo-	k	$10^3$
centi-	c	$10^{-2}$
milli-	m	$10^{-3}$
micro-	\mu	$10^{-6}$
nano-	n	$10^{-9}$

Summary Table: SI Base Units

Quantity	Unit	Symbol
Length	meter	m
Mass	kilogram	kg
Time	second	s
Temperature	kelvin	K
Amount of substance	mole	mol

Additional info: Academic context and examples have been added to clarify brief points and make the notes self-contained for exam preparation.