Accuracy & Precision
Intensive vs. Extensive Properties
Density
Inferences vs. Observations
Making Measurements
100
Define accuracy
How close our measurements are to the accepted/actual value
100
What is an intensive property?
Property that doesn't change with the amount of substance; is unique to the substance
100
What is density?
How compact the atoms are in a substance
100
I think that the mystery orange liquid left on my desk is orange juice. Is that an inference or an observation?
Inference
100
How do we determine how many decimal places to report a measurement to?
We leave one uncertain digit
200
Define precision
How close our measurements are to each other
200
What is an extensive property?
Property that DOES change with the amount of substance
200
I have a rock with a mass of 17.3 g and a volume of 11.8 cm3. What is the density of the rock?
1.47 g/cm3
200
Make three qualitative observations about this classroom
# ppl/desks/chairs in the classroom
200
11.6x cm
300
Ms. Gelfand calculates the density of water, and gets 0.97 g/mL, 0.98 g/mL, and 1.03 g/mL. Are these measurements accurate, precise, both, or neither?
Accurate but not precise
300
Give three examples of intensive properties
odor, taste, density, boiling/melting/freezing point, texture, etc.
300
I have a solid with a density of 0.94 g/cm3. Will it sink or float in water? Why?
Float; density is less than that of water (1.0 g/mL)
300
Make three qualitative observations about this classroom
Color of the walls, bright/dim, etc.
300
Report the measurement in the beaker with the correct number of sig figs
2.6x mL
400
Ms. Gelfand calculated the density of gold as 18.8 g/cm3. The actual density of gold is 19.32 g/cm3 . What is her percent error?
2.69%
400
Give three examples of an extensive property
mass, weight, volume
400
I want to find the density of an irregularly shaped solid. I know its mass is 50g, but I'm having trouble measuring its length, width, and height to find the volume. How can I find the volume of the solid?
Water displacement
400
Which of the following is not an observation:
a. The object is red
b. The object is 12 cm long
c. The object is a marker
d. The object is cylindrical
c
400
Give this measurement to the correct number of significant figures. This measurement is given in inches.
1.3x in
500
Which piece of glassware yields the most precise measurements? Give TWO reasons.
Graduated cylinder
- More tick marks
- Lowest percent error in the measurement lab
500
Ms. Gelfand has a blue liquid in a beaker that she forgot to label. Think of two experiments she could do to try and figure out the identity of the unknown blue liquid.
Any experiment looking at an intensive property
500
I have a solid with the following dimensions:
Mass: 58 g
Length: 8 cm
Width: 4 cm
Height: 5 cm
What is the density of the solid?
0.3625 g/cm3
500
In a CER, should each of the following be composed of an inference, observation, or both?
Claim:
Evidence:
Reasoning:
Claim: Inference
Evidence: Observation
Reasoning: Both
500
Report this measurement to the correct number of sig figs.
2.x cm