Science Basics Quiz

Introduction to Chemistry

• Chemistry is the study of matter—its composition, properties, and transformations.
• Matter is anything that has mass and takes up space (volume).

Types of Matter

• Naturally occurring matter: Cotton, silk, hair, sand, gemstones, digoxin (a cardiac drug).
• Synthetic (human-made) matter: Nylon, polyester, styrofoam, ibuprofen, many antibiotics.
• Matter encompasses all substances forming our world: antacid tablets, water, glass, and air.

Atoms and Matter

• Chemistry is the study of matter's composition, structure, and properties, and the changes it undergoes.
• All matter is made up of basic building blocks called atoms.

Chemicals

• Chemicals are substances with consistent composition and properties across various locations.
• Many common daily uses contain chemicals, such as toothpaste (calcium carbonate, sorbitol, sodium lauryl sulfate, titanium dioxide, triclosan, sodium fluorophosphate, methyl salicylate).
• Kitchen chemicals include silicon dioxide (glass), chemically treated water, metal alloys, natural polymers, and natural gas; fruits grown with fertilizers and pesticides.

The Scientific Method

• It comprises general principles governing scientific thinking.
• Four steps are involved: observation, hypothesis, experimentation, and conclusion.
• Observations are made about nature; a hypothesis is proposed to explain observations.
• Experiments test the hypothesis.
• Conclusions determine if the hypothesis is correct or false.

Examples of Observations, Hypotheses, Experiments, Conclusions. - Study Check Question

• If your friend gets a cat and you start sneezing this can lead to the conclusion that you are allergic to cats.

Classification of Matter

• Pure substance: A substance with definite composition.
  • Elements: Cannot be broken down chemically
  • Compounds: Composed of 2 or more elements joined chemically
• Mixture: Composed of more than one component
  • Homogeneous mixture: Uniform composition throughout; e.g., brass (copper and zinc).
  • Heterogeneous mixture: Non-uniform composition; e.g., water and copper in solution.
  • Examples include salad, dressing, and a mixture of candies.

Measurements

• Measurements always involve a number and a unit.
• The metric system uses units like meters (length), liters (volume), and grams (mass).
• Example: 1 meter = 100 centimeters.
• Exact numbers result from counts or definitions.
• Inexact numbers result from measurements and contain uncertainty.

Significant Figures

• Significant figures (sig figs) refer to the meaningful digits in a measurement.
• Rules for determining significant figures:
  • Non-zero digits are always significant.
  • Zeros between non-zero digits are significant.
  • Zeros at the end of a number containing a decimal point are significant.
  • Zeros at the beginning of a number are not significant.
• Rules for rounding off numbers.
• Rules for addition and subtraction.
• Rules for multiplication and division.

Scientific Notation

• Used to represent very large or very small numbers concisely.
• Consists of a coefficient (between 1 and 10) and an exponent (power of 10).

SI system

• The International System of Units (SI) is the standard system of units used in chemistry.
  • Length (meter, m).
  • Volume (cubic meter, m³).
  • Mass (kilogram, kg).
  • Temperature (Kelvin, K).
  • Time (second, s).

Density

• Density is the relationship between mass and volume.
• Density=Mass/Volume.

Density, Specific Gravity and Temperature Conversions

• Density is the ratio of mass to volume.
• Specific gravity is the ratio of the density of a substance to the density of water.
• Temperature conversions between Celsius, Fahrenheit, and Kelvin.