PRAXIS 5246 · COURSE
Praxis 5246 Chemistry: Content Knowledge course
27 guided lessons across 5 sections. Read the first chapter free — no account needed.
FREE CHAPTER
Variables and measurement
Why does variables and measurement matter on the Chemistry exam? It helps you interpret evidence instead of memorizing a label.
Key words
- Variables and measurement
- A fair investigation changes one independent variable, measures a dependent variable, and controls relevant conditions. — e.g. Measure reaction rate at three temperatures using equal reactant concentrations.
- Evidence
- Observations or measurements used to evaluate a claim about variables and measurement. — e.g. Measure reaction rate at three temperatures using equal reactant concentrations.
- Mechanism
- The causal process that explains how variables and measurement works. — e.g. A fair investigation changes one independent variable, measures a dependent variable, and controls relevant conditions.
- Prediction
- An expected result derived from a testable model of variables and measurement. — e.g. Identify temperature as the independent variable and gas volume per minute as the response.
- Misconception
- An appealing but incorrect explanation about variables and measurement. — e.g. Changing concentration and temperature together confounds interpretation.
IDEA
A fair investigation changes one independent variable, measures a dependent variable, and controls relevant conditions.
IN EVERYDAY WORDS
Start with this concrete situation: Measure reaction rate at three temperatures using equal reactant concentrations.
WHAT PEOPLE MIX UP
Changing concentration and temperature together confounds interpretation.
I DO — MODEL
I read the situation, name the relevant process, and test my claim against the evidence. Identify temperature as the independent variable and gas volume per minute as the response.
WE DO — GUIDED
Work through the example together: Measure reaction rate at three temperatures using equal reactant concentrations. First identify the evidence; next apply the rule; finally explain why a tempting misconception fails: Changing concentration and temperature together confounds interpretation.
Remember this
- A fair investigation changes one independent variable, measures a dependent variable, and controls relevant conditions.
- Identify temperature as the independent variable and gas volume per minute as the response.
- Avoid this mistake: Changing concentration and temperature together confounds interpretation.
VARIABLES AND MEASUREMENT: EVIDENCE → RULE → CHECK THE MISCONCEPTION.
Every lesson in the course
I. Nature and Impact of Science and Engineering
14%- Variables and measurementFree
- Precision and significant figures
- Chemical laboratory safety
- Scientific models of matter
- Energy technology and environment
II. Principles and Models of Matter and Energy
25%- Atomic structure and isotopes
- Electron configuration
- Gas laws and particles
- Thermochemistry
- States and phase changes
- Kinetics and catalysts
III. Chemical Composition, Bonding, and Structure
20%- Ionic and covalent bonds
- Lewis structures and geometry
- Polarity and intermolecular forces
- Moles and formula mass
- Stoichiometry and limiting reactants
IV. Chemical Reactions and Periodicity
23%- Periodic trends
- Balancing and conservation
- Oxidation and reduction
- Equilibrium and Le Châtelier
- Reaction rates and mechanisms
- Thermodynamics and spontaneity
V. Solutions and Acid-Base Chemistry
18%- Molarity and dilution
- Solubility and equilibrium
- Acids bases and pH
- Buffers and titration
- Colligative properties