Introduction to Chemistry and Matter: Foundations for General Biology

Defining Chemistry

What is Chemistry?

Chemistry is the scientific study of the composition, structure, properties, and changes of matter. It emerged from the experimentation of alchemists and forms the basis for understanding biological processes at the molecular level.

• Chemistry: The study of matter and the changes it undergoes.

• Originated from alchemy, which involved early experimentation with substances.

Five Areas of Chemistry

Chemistry is divided into several specialized fields, each focusing on different aspects of matter and its interactions.

• Organic chemistry: Study of all chemicals containing carbon.

• Inorganic chemistry: Study of chemicals that do not contain carbon.

• Biochemistry: Study of the chemistry of living things.

• Analytical chemistry: Study of the composition of matter.

• Physical chemistry: Study of the mechanisms, rates, and energy transfer that occur when matter changes.

Example: Biochemistry is essential for understanding cellular processes such as metabolism and DNA replication.

Why Study Chemistry?

Importance of Chemistry

Chemistry is fundamental to many scientific disciplines, including biology. It helps explain natural phenomena, prepares students for scientific careers, and enables informed decision-making.

• Explains everyday processes (e.g., digestion, photosynthesis).

• Prepares for careers in science, medicine, engineering, and more.

• Enables informed decisions about health, environment, and technology.

Roots of Chemistry: Alchemy

Historical Background

Alchemy was practiced in various cultures and laid the groundwork for modern chemistry through experimentation and the development of laboratory techniques.

• Practiced in Arabia, China, and Greece.

• Goals included making gold, creating potions for eternal life, and understanding matter.

• Developed practical lab procedures: distillation, sublimation, oxidation, extraction.

• Learned and passed on properties of substances.

• Tools and techniques from alchemy are still used today, though alchemy lacked logical explanations for changes in matter.

Studying Chemistry: The Scientific Method

Systematic Approach

Scientists use the scientific method to investigate questions and solve problems in chemistry and biology.

• Make observations

• Formulate hypotheses

• Experiment

  • Manipulated variable: The variable that is changed.

  • Responding variable: The variable that is observed for changes.

  • Collect data: Can be qualitative (descriptive) or quantitative (numerical).

• Draw conclusions

Example: Testing the effect of temperature on enzyme activity involves manipulating temperature and measuring reaction rates.

Matter: Definition and Properties

What is Matter?

Matter is anything that has mass and occupies space. Understanding matter is essential for studying biological systems.

• Mass: Measure of the amount of matter in an object.

• Volume: Measure of the space occupied by an object.

Physical Properties of Matter

Physical properties are characteristics that can be observed or measured without changing the substance's composition.

• Examples: Color, boiling point, melting point.

States of Matter

Matter exists in different states, each with distinct physical properties.

• Solid: Definite shape and volume; shape does not depend on container; particles tightly packed; almost incompressible; expands slightly when heated.

• Additional info: Other states include liquid and gas, which have different properties regarding shape, volume, and particle arrangement.

Measurement in Science

Measurement: Quantity and Unit

Measurements are fundamental to experimental science and require both a number and a unit.

• Use the SI/Metric System (e.g., km, cm, mL).

• Measurements should be correct and reproducible.

Accuracy and Accepted Value

Accuracy refers to how close a measurement is to the true or accepted value.

• Accepted Value (AV): The correct value based on reliable references.

Significant Figures

Definition and Rules

Significant figures (sig figs) are all the digits in a measurement that are known, plus one last digit that is estimated. They are important for expressing the precision of measurements.

• Nonzero digits always count as significant.

• Zeros count as significant depending on their position (e.g., trailing zeros in a decimal number).

• Exact numbers (e.g., counting numbers, defined conversions) have an infinite number of significant figures and are not limited by measurement precision.

Example: The number 7 bananas is an exact number; 7.62 cm has three significant figures.

Scientific Notation

Purpose and Format

Scientific notation is used to express very large or very small numbers in a concise form, making calculations and communication easier.

• A number is written as the product of a coefficient and 10 raised to a power.

• Numbers greater than 1 have a positive exponent; numbers less than 1 have a negative exponent.

Example: $5.19 \times 10^{-14}$

Density: Comparing Mass and Volume

Definition and Formula

Density is an intensive property that describes the ratio of mass to volume for a substance. It is independent of the amount of substance present.

• Formula:

$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

• Measured in units such as g/cm3 or kg/m3.

• Density depends on the composition of the substance, not the amount.

Density and Temperature

The density of a substance generally decreases as its temperature increases because volume increases while mass remains the same.

Density and Pressure

The density of a substance generally increases as its pressure increases because volume decreases while mass remains the same.

Property	Effect of Temperature	Effect of Pressure
Density	Decreases (volume increases)	Increases (volume decreases)

Additional info: Understanding density is important in biology for processes such as cell separation and fluid dynamics.