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What would be an example of a set of measurements that are both accurate and precise?
Example Answer - A student's measured value is 9.8 g/mL, and the accepted value is 9.8 g/mL.
How many significant figures are in the measurement 430.0 cm?
4 sig figs
What are the 3 rules to protect the balances and ensure accurate results?
Always check the balance is level and zeroed before using it
Never mass objects directly on the balance pan.
Use weight paper/boat to protect it, never mass hot or cold items
What is an accepted value?
the most accurate and valid measurement for a quantity
Why shouldn't the thermometer touch the bottom of the container, and what will happen if it does?
Because the container's bottom could be a different temperature from the substance, leading to inaccurate results.
What is the term for how close a series of measurements is to one another?
Precision
How many significant figures are in the measurement 0.0050 g?
2 sig figs
What are the units for measuring mass, volume, and length?
Grams, C, and mL
What are 3 things that could affect accuracy?
Skill of the Measurer
Calibration of the Instrument [balances]
Loss of reactant or product
What is the Definition of a Graduated Cylinder?
A graduation is a mark on an instrument that indicates increments and quantities
A dart player hits the same spot on a dartboard five times, but it's not the bullseye. Is this an example of accuracy or precision?
Precision
A measurement of 0.7020 mL has how many significant figures?
4 sig figs
A scientist measures a solid object on the balance. What should she do with the final mass reading?
Include the correct units (e.g., grams or kilograms) and the appropriate number of significant figures.
What is the formula for percent error using the value experiment and the value accepted?
(experimental value - accepted value)
-------------------------------------------------------- x 100
accepted value
How do you read a graduated cylinder, and what is a Meniscus?
- Read volume from the bottom of the Meniscus (at eye level)
- A meniscus is the curved surface of a liquid in a tube
A student measures the mass of a 10.0-gram weight three times and gets 9.9 g, 10.1 g, and 10.0 g. Is the student's measurement accurate, precise, or both?
It's both Accurate and Precise
What is the result of 12.55 g + 5.2 g, rounded to the correct number of significant figures?
17.8 g
When measuring a solid, where should the substance be placed on the balance?
On a piece of weighing paper or in a beaker, never directly on the scale itself.
A student measures the boiling point of ethanol to be 75.0°C. The accepted value is 80.0°C. What is the percent error?
6.3%
((75.0-80.0)/80.0) x 100
What are 2 things you should do before and after using a balance?
Check the balance is level and at zero
When you use a ruler to measure a 10 cm line and you repeatedly get 10.1 cm, 10.0 cm, and 9.9 cm.
Is it Accurate, Precise, Both, Accurate and Precise, Precise and not Accurate, or Accurate and not Precise?
Accurate but not precise
What is the result of 4.50 cm x 2.0 cm, rounded to the correct number of significant figures?
9.0 cm2
What rider should you start with when using the triple-beam balance and where should the arm be when moving the notch?
The Largest Rider
The arm should be below zero
You want to find the percent error for your experimental value of 15.6 cm, but you find that your percent error is 35.5%.What are the two possible values for the actual measurement?
Positive error : x = 11.5
- 35.5 = ((15.6 - x)/x) X 100
Negative error : x = 24.2
- -35.5 = (( 15.6 - x)/x) X 100
What is the conversion: 100 centimeters equals how many meters? 10 millimeters equals how many centimeters? 1000 millimeters equals how many meters? 1 millimeter equals how many centimeters?
- 100 centimeters equals 1 meter
- 10 millimeters equals 1 centimeter
- 1000 millimeters equals 1 meter
- 1 millimeter equals 0.1 centimeters