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 our daily lives.

• 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: Noting and recording facts about nature.

• Hypothesis: A possible explanation for an observation, which can be tested by experiments.

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

• Conclusion: A decision made about the hypothesis based on the results of the experiment. The conclusion determines whether the hypothesis is true or false.

Measurement and Units

Chemistry relies on precise measurement. The metric system and SI (International System of Units) are standard systems used in science.

• Volume: The space occupied by a substance. SI unit: liter (L). Useful relationships: $1~L = 1000~mL$, $1~L = 1.06~qt$.

• Length: The distance between two points. SI unit: meter (m). Useful relationships: $1~m = 100~cm$, $1~m = 39.4~in$, $1~in = 2.54~cm$, $1~m = 1.09~yd$.

• Mass: The quantity of material an object contains. SI unit: kilogram (kg). Useful relationships: $1~kg = 1000~g$, $1~lb = 454~g$, $1~kg = 2.2~lb$.

• Temperature: A measure of how hot or cold an object feels. SI unit: Kelvin (K). Celsius (°C) is also commonly used. Water freezes at $0^ ext{°C}$ ($273~K$), boils at $100^ ext{°C}$ ($373~K$). Absolute Zero is the lowest possible temperature ($0~K$).

• Time: Based on atomic clock. SI unit: second (s).

Metric Prefixes

Prefixes are attached to units to indicate multiples or fractions of the base unit.

Prefix	Symbol	Meaning	Value
kilo	k	thousand	$10^3$
centi	c	hundredth	$10^{-2}$
milli	m	thousandth	$10^{-3}$
micro	μ	millionth	$10^{-6}$

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 point to the left: Positive power of 10.

• Moving the decimal point 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 and 95 other balls.

• Example: 50% green balls in 100 balls means 50 green balls and 50 other balls.

Graphs

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

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

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

• Slope of a Line: $\text{slope} = \frac{\text{rise}}{\text{run}}$

Solving Equations

Equations can be rearranged to solve for unknown variables.

• Example: Solve $2x + 8 = 14$

  1. Place all like terms on one side: $2x = 14 - 8$

  2. Calculate: $2x = 6$

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

Reporting Length

To report the length of an object:

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

• Estimate the last digit by visually dividing the space between the marked lines.

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

• Example: If the ruler shows 4.5 cm, and you estimate the next digit, you report 4.53 cm.

Significant Figures

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

• All nonzero numbers are significant.

• Zeros between nonzero digits are significant.

• Zeros at the beginning of a number are not significant.

• Zeros at the end of a number with a decimal point are significant.

• Example: $0.0054$ has 2 significant figures; $54.00$ has 4 significant figures.

Rule	Example	Number of Significant Figures
Nonzero digits	24	2
Zeros between nonzero digits	205	3
Leading zeros	0.003	1
Trailing zeros with decimal	50.0	3
Trailing zeros without decimal	400	1

• How to make one zero in 44000 significant: Write as $4.4 \times 10^4$

Unit Conversion

Unit conversion is essential for solving problems in chemistry. Conversion factors are ratios that express how many of one unit are equal to another unit.

• Example: $1~L = 1000~mL$

• Example: $1~kg = 1000~g$

• Example: $1~in = 2.54~cm$

Summary Table: SI and Metric Units

Quantity	SI Unit	Metric Unit	US Customary Unit
Length	meter (m)	meter (m)	yard (yd), inch (in)
Mass	kilogram (kg)	gram (g)	pound (lb), ounce (oz)
Volume	cubic meter (m3)	liter (L)	quart (qt), gallon (gal)
Temperature	kelvin (K)	celsius (°C)	degree Fahrenheit (°F)
Time	second (s)	second (s)	second (s)

Additional info:

• Some context and examples have been expanded for clarity and completeness.

• Scientific notation and significant figures are crucial for reporting measurements accurately in chemistry.

• Understanding unit conversions and the metric system is foundational for all GOB Chemistry calculations.