Classification of Matter

Pure Substances vs. Mixtures

Matter is anything that has mass and occupies space. It can be classified into pure substances and mixtures based on its composition.

• Pure Substance: Made up solely of one substance and can be represented by a singular formula.

  • Element: Composed of only one type of atom. Examples: diamond, copper.

  • Compound: Contains two or more elements chemically joined together in a fixed proportion. Examples: water, table salt, glucose.

• Mixture: Contains two or more substances.

  • Homogeneous Mixture: Composition is the same throughout the sample. Example: brass (copper and zinc alloy).

  • Heterogeneous Mixture: Composition varies throughout the sample, may include different matter states. Example: trail mix, salad.

The Periodic Table and Nutrients

Macronutrients and Micronutrients

The periodic table organizes elements by increasing atomic number and groups elements with similar chemical properties. Certain elements are essential for human nutrition.

• Macronutrients: Required in amounts ≥ 100 mg/day. Examples: Na, Mg, K, Ca, P, S, Cl.

• Micronutrients: Required in amounts < 100 mg/day. Examples: Mn, Fe, Mo, Cu, Zn, F, Se, I.

Physical and Chemical Changes

Types of Changes in Matter

Matter can undergo physical or chemical changes, which affect its properties and identity.

• Physical Change: Change in state of matter (solid, liquid, gas) while the chemical identity remains the same. Examples: melting, boiling, freezing.

• Chemical Change: Change in the chemical identity of the substance(s) involved, often involving breaking and forming chemical bonds. Examples: rusting, burning, combustion, tarnishing.

• Law of Conservation of Matter: Matter cannot be created or destroyed in a chemical reaction.

Example of Chemical Reaction:

• Reactants: C(s), O2(g); Product: CO2(g)

Measurement and Units

Metric Prefixes and US Conversion Factors

Measurements in chemistry use standardized units. The metric system is commonly used, but US customary units may also appear.

• Metric Prefixes:

• US Conversion Factors:

  • 2.54 cm = 1 in.

  • 1 kg = 2.205 lb.

  • 1 oz = 29.6 mL

  • 1 mi = 1.609 km

  • 1000 mL = 1 L

  • 1 L = 1.06 qt

  • 4 qt = 1 gal

Significant Figures

Rules and Application

Significant figures indicate the precision of a measured value. They are important in calculations to ensure accuracy.

• Nonzero digits are always significant.

• Zeros between nonzero digits are significant.

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

• Leading zeros are not significant.

• Trailing zeros in a number without a decimal point are not significant.

• For addition/subtraction: answer must have the lowest number of decimal places of the involved values.

• For multiplication/division: answer must have the lowest number of significant figures of the involved values.

Density, Specific Gravity, and Temperature

Definitions and Formulas

These physical properties are essential for characterizing substances in chemistry.

• Density: Mass per unit volume. Formula:

• Specific Gravity: Ratio of the density of a sample to the density of water. Formula:

• Temperature Conversions:

  • Kelvin = Celsius + 273

Energy and Heat

Types and Measurement

Energy is the capacity to do work or supply heat. It exists in various forms and is measured in calories or joules.

• Potential Energy: Stored chemical energy.

• Kinetic Energy: Energy of motion.

• Calorie (cal): Energy unit; 1 cal = 4.184 J.

• Calorie (Cal): Used on nutrition labels; 1 Cal = 1000 cal.

• Heat: Kinetic energy flowing from a warmer body to a colder one.

• Specific Heat Capacity: Amount of heat needed to raise the temperature of 1 g of a substance by 1 °C.

Measurement Accuracy and Precision

Definitions

Accuracy and precision are important concepts in scientific measurement.

• Accuracy: How close a measurement is to the true value.

• Precision: How reproducible measurements are when repeated under unchanged conditions.

Nutrition Calculations

Percent Daily Value

Nutrition labels provide information about the content of nutrients in food. The percent daily value helps consumers understand the contribution of a nutrient to their daily diet.

• Formula:

• Example: If a serving contains 2.4 g of sodium and the daily suggested amount is 2.4 g, then Daily Value.

Additional info: Nutrition calculations may require unit conversions, such as mg to g (1 g = 1000 mg).