Lab Techniques

Parts of the Bunsen Burner

The Bunsen burner is a common laboratory device used to produce a single open gas flame for heating, sterilization, and combustion.

• Base: Provides stability and connects to the gas supply.

• Gas Inlet: Where the gas enters the burner.

• Barrel: The vertical tube where gas and air mix before combustion.

• Collar (Air Regulator): Adjusts the amount of air mixing with the gas, controlling the flame's temperature and color.

• Needle Valve: (if present) Fine-tunes the gas flow.

How a Bunsen Burner Works and How to Adjust It

• Gas flows through the inlet and mixes with air in the barrel.

• Adjusting the collar increases or decreases air intake, changing the flame from yellow (cool, incomplete combustion) to blue (hot, complete combustion).

• Open the collar for a hotter, blue flame; close for a cooler, yellow flame.

Separation/Filtration Vocabulary

• Filtration: Separating solids from liquids using a porous material (e.g., filter paper).

• Residue: The solid left on the filter paper.

• Filtrate: The liquid that passes through the filter.

• Decantation: Pouring off a liquid to separate it from a solid.

• Evaporation: Removing a liquid by heating to leave behind a solid.

Safety Rules and Equipment

Laboratory safety is essential to prevent accidents and ensure a safe working environment.

• Always wear appropriate personal protective equipment (PPE): goggles, lab coat, gloves.

• Know the location and use of safety equipment: fire extinguisher, eyewash station, safety shower, first aid kit.

• No eating or drinking in the lab.

• Report all accidents and spills to the instructor immediately.

• Dispose of chemicals according to instructions.

Graphing

Independent vs. Dependent Variable

• Independent Variable: The variable you change or control (plotted on the x-axis).

• Dependent Variable: The variable you measure (plotted on the y-axis).

• Example: In a temperature vs. time graph, time is independent, temperature is dependent.

Calculating Range and Scale

• Range: Difference between the highest and lowest values in a data set.

• Scale: The value each division on an axis represents; choose a scale that fits the data and uses most of the graph area.

Creating and Reading Graphs

• Label axes with variable names and units.

• Plot data points accurately.

• Draw a best-fit line or curve if appropriate.

• Read values by tracing from the graph to the axes.

Measurements

Metric System Units

• Length: meter (m)

• Mass: gram (g)

• Volume: liter (L)

• Temperature: degrees Celsius (°C) or Kelvin (K)

Unit Conversions/Dimensional Analysis

• Use conversion factors to change units.

• Set up conversion so units cancel appropriately.

Example: Convert 25 cm to meters:

Significant Figures

• Digits in a measurement that are known with certainty plus one estimated digit.

• Rules:

  • Nonzero digits are always significant.

  • Zeros between nonzero digits are significant.

  • Leading zeros are not significant.

  • Trailing zeros are significant only if there is a decimal point.

Reading Volume from a Graduated Cylinder

• Read at the bottom of the meniscus at eye level.

• Estimate one digit beyond the smallest graduation.

Calculating Density Using Water Displacement

• Density is mass per unit volume.

• Use water displacement to find the volume of irregular objects.

Formula:

Example: If a metal weighs 15.0 g and displaces 2.0 mL of water, density is:

Using Other Lab Equipment

• Thermometer: Measures temperature; read at eye level.

• Analytical Balance: Measures mass to high precision; ensure balance is zeroed before use.

Precision vs. Accuracy

• Precision: How close repeated measurements are to each other.

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

Calorimetry and Specific Heat

Heat (q) and Specific Heat Calculations

Calorimetry is the measurement of heat transfer during physical or chemical changes.

• Specific Heat (c): The amount of heat required to raise the temperature of 1 gram of a substance by 1°C.

• Formula:

• Where q = heat (J), m = mass (g), c = specific heat (J/g°C), ΔT = change in temperature (°C).

Example: If 50.0 g of metal increases in temperature by 10.0°C and absorbs 420 J of heat, the specific heat is:

Acids, Bases, and Salts

Green Chemistry

• Designing chemical processes to reduce or eliminate hazardous substances.

• Focuses on sustainability and environmental safety.

Vocabulary

• Acid: Substance that donates a proton (H+) in solution.

• Base: Substance that accepts a proton or donates OH- in solution.

• Salt: Ionic compound formed from the reaction of an acid and a base.

• Electrolyte: Substance that conducts electricity when dissolved in water.

Experiment Solutions

• Solutions are homogeneous mixtures of solute and solvent.

• Acids, bases, and salts can all form solutions in water.

Determining pH Given Indicator Data

• pH is a measure of hydrogen ion concentration; scale ranges from 0 (acidic) to 14 (basic).

• Indicators change color depending on pH; compare color to a reference chart to determine pH.

Separations

Using a Lab Notebook

• Record all procedures, observations, and data clearly and in ink.

• Include date, experiment title, and purpose.

• Do not erase; cross out errors with a single line.

Separating a Mixture

• Use physical properties (e.g., solubility, magnetism, boiling point) to separate components.

• Common methods: filtration, evaporation, decantation, chromatography.

Calculating Mass Percent

• Mass percent expresses the mass of a component as a percentage of the total mass of the mixture.

Formula:

Example: If a mixture contains 2.0 g salt and 8.0 g sand, the mass percent of salt is:

Additional info: Academic context and definitions have been expanded for clarity and completeness. Table summarizes key separation and solution terms.