Measurement and Units
This SI base unit is used to measure mass
kilogram (kg)
What is accuracy?
closeness to the true value
What is a liquid?
Liquid — definite volume, no definite shape
What is a trial?
When scientists repeat an experiment several times to improve their results, each repetition is called one of these.
What does F and A stand for?
Force and Area
What is 5.6 × 10⁻⁷ m
0.00000056 = move decimal 7 places → 5.6 × 10⁻⁷
What is random error
Random error causes differences with no recognizable pattern between repeated trials
What is evaporation?
Evaporation happens at surface below boiling point
Why should we increase the number of trials?
More trials reduces random error through averaging
A force of 10 N acts on an area of 2 m².
What is the pressure on the surface?
Pressure = Force ÷ Area)
→ Answer: 5 Pa
What is 2500 m in scientific notaion?
2.50 × 10³ m
How do you find an average?
Add all the values and divide by the amount of values added.
What is the melting point?
Melting point is the temperature where solid and liquid coexist; on a heating curve it’s the plateau
Calculate the average: 10.2 g, 10.3 g, 9.8 g, 10.1 g, 10.2g
10.2 + 10.3 + 9.8 + 10.1 + 10.2 = 50.6 → mean = 50.6 ÷ 5 = 10.12 g
At constant pressure, heating a gas increases temperature. What happens to the volume?
It also increases. They are directly proportional.
What is calibration?
Calibration adjusts an instrument to reduce systematic error
What is a systematic error? What are some causes?
An error with a standard pattern, often cause by uncallibrated instruments or incorrect procedure.
Why does honey flow more slowly than water?
Honey has higher viscosity
Viscosity is resistance to flow because particle interactions are stronger
The true value is 32.4 m, a student measured it to be 32 m. What is the error?
32.4 m - 32 m = 0.4 m error
An object has a mass of 25 g and a volume of 5.0 cm³.
Find its density in g/cm³.
25 ÷ 5.0 = 5.0 g/cm³
What show more precision, 15.2 or 15.200? Why?
15.200 shows more precision because we know that the measurement instrument had a more specific value.
A student measures the mass of a 100.0 g standard five times and records: 98.7 g, 99.1 g, 98.9 g, 99.0 g, 98.8 g. Calculate the average error?
(98.7 + 99.1 + 98.9 + 99.0 + 98.8) = 494.5 → mean = 494.5 ÷ 5 = 98.9 g
100 g - 98.9 g = 1.1 g or error
A student heats a solid and records a steady increase in temperature until it reaches 45°C. The temperature then stays the same for several minutes even though the student keeps adding thermal energy. Explain what is happening to the substance during this time and why the temperature does not rise.
the substance is melting, and the added thermal energy is being used to change the state of matter (solid to liquid) instead of increasing temperature
A student calculates an average mass of 50.2 g for five trials, but the true mass is 49.0 g. Explain what this difference tells you about the accuracy of the data.
the data are not very accurate because the average is higher than the true value. (Percent difference 2.4%)
A diver experiences a force of 2,000 N over an area of 0.50 m².
Calculate the pressure in pascals.
2,000 ÷ 0.50 = 4.0 × 10³ Pa