Matter, Measurement & Sig Figs
Review classifying matter, SI units, dimensional analysis, and significant figure rules from the chemistry lesson.
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Questions Covered in This Set
10 cards to master
What is matter?
Anything that has mass and takes up space.
Element vs. compound
An element is one type of atom (Cu, O₂); a compound is two or more elements chemically bonded in fixed ratios (H₂O, NaCl) and can only be separated chemically.
Homogeneous vs. heterogeneous mixture
Homogeneous (a solution) is uniform throughout — salt water, air, brass. Heterogeneous has visible distinct regions — sand in water, granite, Italian dressing.
Name four signs of a chemical change.
Gas bubbles without boiling, color change, temperature change not caused by heating, formation of a precipitate (also light or odor production).
Convert 25 °C to Kelvin.
K = °C + 273.15, so 25 °C = 298.15 K.
What is dimensional analysis?
Multiplying by fractions equal to 1 so unwanted units cancel — e.g., 2.50 km × (1000 m/1 km) × (100 cm/1 m) = 2.50 × 10⁵ cm.
Density formula and an example
d = m/V. 27.0 g of aluminum in 10.0 cm³ gives 2.70 g/cm³; density can also be used as a conversion factor.
Accuracy vs. precision
Accuracy is closeness to the true value; precision is closeness of repeated measurements to each other. A scale always 5.00 g high is precise but inaccurate.
How many sig figs in 0.0042, 2.006, and 1.200?
0.0042 → 2 (leading zeros don't count); 2.006 → 4 (zeros between nonzeros count); 1.200 → 4 (trailing zeros count with a decimal point).
Which numbers are infinitely precise?
Exact counted numbers and definitions — 12 eggs, 1 km = 1000 m exactly — they never limit sig figs.
