Scientific Method &
Precision/Accuracy
Precision/Accuracy
Let's say the CORRECT or ACCEPTED answer to a problem is 75.0 mL. Is the following data set accurate, precise, both, or neither?
61.1 mL, 61.2 mL, 61.0 mL
Precise, but not accurate.
Write 0.00044560 in scientific notation.
4.4560 x 10-4
What is the equation for density?
Density = mass/volume
Is the following an equivalence statement or a conversion factor?
1 foot = 12 inches
Equivalence statement
Which type of matter has no fixed shape and expands to fill its container?
What is the difference between independent and dependent variables?
The variable that is deliberately changed is called the independent variable. The variable that is observed and changes in response to the manipulated variable is called the dependent variable.
Write 4.953 x 104 in standard form.
49,530
What units do we use for solids when measuring density?
g/cm3
When determining sig figs for our final answer in dimensional analysis, what do we ignore?
The sig figs in conversion figures
What is the difference between extensive and intensive properties?
Extensive is dependent on amount of substance, while intensive is independent of the amount of substance.
An object has a mass of 35.0 grams. On Anthony’s balance, it weighs 34.85 grams. What is the percent error of the balance?
% error = | (34.85-35.0)/35.0 | x 100 = 42.86%
Complete the following problem. Use correct sig figs to answer.
2.33 / 70 =
0.03
What unit do we use for liquids when measuring density?
g/mL
How many grams are in a kilogram? Show work!
1,000 g in 1 kilogram
Are the following signs of a physical change or chemical change?
Gas, light, heat
Chemical change
What is the difference between accuracy and precision?
Accuracy is how close a value is to the accepted value. Precision is the ability to reproduce a value.
Complete the following problem. Use correct sig figs to answer.
45.1 + 8,456 + (3.1 x 105) =
32,000
What is the density of a block of wood that has dimensions of 3.2 cm x 2.25 cm x 1.25 cm? The mass of the block is 15 g.
Doesn't count if you use incorrect sig figs!
1.7 g/cm3
How many pints are in 30. gallons? Remember sig figs!
(30 gallons) (8 pints/1 gallon) = 240 pints
Label the following as element (E), compound (C), or mixture (M).
1. Mercury (Hg)
2. Milk
3. Water (H2O)
1. Element
2. Mixture
3. Compound
What are the six steps of the scientific method?
Ask a question
Perform research
Write a hypothesis
Set up and perform an experiment
Record data, analyze results, and write a conclusion
Communicate your findings
What are the four rules for significant figures?
1. Non-zero numbers are always significant.
2. Zeros between non-zero numbers are always significant.
3. Leading zeros before the first non-zero number are not significant.
4. Trailing zeros, coming after non-zero numbers, are significant IF there is a decimal point in the number.
An object has a density of 2.50 g/cm³. Before being placed in water, to volume reads 10.0 mL. After dropping the object in, the volume reads 17.5 mL. What is the mass of the object?
Doesn't count if you use incorrect sig figs!
18.6 g
How many days are in 150,000 seconds? Remember sig figs!
(150,000 seconds) (1 minute/60 seconds) (1 hour/60 minutes) (1 day/24 hour) = 1.7 days
Label the following as chemical (C) or physical (P) change:
1. Melting
2. Baking
3. Painting a car
4. Frying fish
1. Physical
2. Chemical
3. Physical
4. Chemical