Chapter 1: Chemistry in Our Lives – GOB Chemistry Study Notes

Chapter 1: Chemistry in Our Lives

Definitions

This section introduces foundational terms and concepts essential for understanding chemistry and its role in everyday life.

• Chemistry: The study of composition, structure, properties, and reactions of matter.

• Composition: What a substance is made of.

• Structure: How the components of a substance are put together.

• Properties: The characteristics that define a substance.

• Reactions: How substances interact with other substances.

• Matter: Anything that has mass and occupies space; all substances that make up our world.

• Chemicals: Substances that have the same composition and properties wherever found.

The Scientific Method

The scientific method is a systematic approach used by scientists to investigate phenomena, acquire new knowledge, or correct and integrate previous knowledge.

• Observation: Gathering information about nature and phenomena.

• Hypothesis: A tentative explanation or prediction that can be tested by experiments.

• Experiment: A procedure carried out to test the hypothesis.

• Conclusion: A decision about whether the hypothesis is true or false, based on experimental results.

Measurement and Units

Chemistry relies on precise measurement. The SI (International System of Units) is used for consistency in scientific communication.

• Volume: The space occupied by a substance. SI unit: liter (L). Useful relationships:

  • $1~L = 1000~mL$

  • $1~L = 1.06~qt$

• Length: SI unit: meter (m). Useful relationships:

  • $1~m = 100~cm$

  • $1~m = 39.4~in$

  • $1~in = 2.54~cm$

• Mass: SI unit: kilogram (kg). Useful relationships:

  • $1~kg = 1000~g$

  • $454~g = 1~lb$

• Temperature: SI unit: Kelvin (K). Chemistry often uses Celsius ($^ ext{o}$C).

  • Water freezes at $0^ ext{o}$C ($32^ ext{o}$F)

  • Water boils at $100^ ext{o}$C ($212^ ext{o}$F)

  • $0~K = -273.15^ ext{o}$C$

  Absolute Zero: The lowest possible temperature, where molecular motion stops.

• Time: SI unit: second (s).

Prefixes and Conversion Factors

Prefixes are used to indicate multiples or fractions of units. Conversion factors help convert between units.

• Common Prefixes:

  • kilo- ($10^3$)

  • centi- ($10^{-2}$)

  • milli- ($10^{-3}$)

• Conversion Example: $1~kg = 1000~g$

Scientific Notation

Scientific notation is used to express very large or very small numbers in a compact form.

• Format: $N imes 10^n$, where $N$ is a number between 1 and 10, and $n$ is an integer.

• Example: $2400 = 2.4 imes 10^3$

• Moving the Decimal:

  • Move to the left: positive power of 10

  • Move to the right: negative power of 10

Percentage

A percentage (%) represents the number of parts of an item in 100 of those items.

• Example: 5% red balls in 100 balls means 5 red balls.

• 50% green balls in 100 balls means 50 green balls.

Graphs and Relationships

Graphs visually represent relationships between variables. The independent variable is plotted on the x-axis.

• Direct Relationship: When the line on the graph indicates that as one variable increases, the other also increases.

• Line of Best Fit: A straight line that best represents the data on a scatter plot.

• Slope Formula:

  • $ext{slope} = \frac{ ext{rise}}{ ext{run}} = \frac{y_2 - y_1}{x_2 - x_1}$

Solving Equations

Equations can be rearranged to solve for unknown variables.

• Example: Solve $2x + 8 = 14$

  1. Subtract 8 from both sides: $2x = 6$

  2. Divide both sides by 2: $x = 3$

Reporting Length

To report the length of an object:

• Observe the marked lines at the end of the object.

• Estimate the last digit by visually dividing the space between the marks.

• The estimated number is the final digit reported for a measured number.

• Example: If the object ends between 4.5 and 4.6 cm, report as 4.55 cm.

Significant Figures

Significant figures (SFs) are the digits in a measured number that are known with certainty plus one estimated digit.

• Rules for Significant Figures:

Rule	Example	Number of Significant Figures
All nonzero digits are significant	51.8	3
Zeros between nonzero digits are significant	50.3	3
Zeros at the beginning are not significant	0.008	1
Zeros at the end and after the decimal are significant	60.0	3
Zeros at the end without a decimal are not significant	40000	1

• How to make zeros significant: Use scientific notation. For example, $4.4000 \times 10^4$ has 5 significant figures.

Units Table

The following table summarizes common SI and US units for measurement:

Quantity	SI Unit	Metric Unit	US Unit
Mass	kilogram (kg)	gram (g)	pound (lb), ounce (oz)
Length	meter (m)	centimeter (cm)	yard (yd), inch (in)
Volume	liter (L)	milliliter (mL)	quart (qt), gallon (gal)
Temperature	Kelvin (K)	Celsius (°C)	degree Fahrenheit (°F)
Time	second (s)	second (s)	second (s)

Additional info:

• These notes cover introductory concepts in GOB Chemistry, including measurement, scientific notation, significant figures, and basic scientific methodology.

• Examples and tables have been expanded for clarity and completeness.