Question

experiment 1: thickness
pre lab questions

1. what is the meaning of accuracy?

how close your measurement is to a accepted value.

1. what is the meaning of precision?

how close your measurements are to each other

1. draw a sketch using a dartboard, in which the bulls eye is the most accurate set of shots it indicates.

high precision and accuracy high precision and poor accuracy poor precision and poor accuracy

1. determine the number of significant figures in the following measurements:

a. 83.239 g 5
b. 100 ml 3
c. 0.0023 kg 2
d. 6.3*10^5 s 2

1. an object travels 59.23 meters in 13 seconds. calculate the speed of that object in meters per second. make sure you express your answer to the correct number of significant figures.

59.23 m/13 s = 4.6 m/s

1. explain why you choose the number of significant figures on your answer for question 5.
2. a student makes a series of measurements and the date is shown below:

mass of object: 83.212 g
initial volume of water: 69.2 ml
volume of water + object: 91.2 ml
volume of object: 22.0 ml
density of object: 3.78 g/ml
complete the calculations and find the density of the object. make sure you express your answer to the correct number of significant figures.
objectives
students will practice making precise measurements and using significant figures in measurements and calculations, to accurately and precisely measure the thickness of al foil.
materials
rectangular piece of al foil (3 pieces), metric ruler, electronic balance (can also use triple beam balance)
procedure

1. measure the length and width of your rectangular piece of foil to the precision of your ruler and record in your data table in centimeters.
2. mass the foil to the precision of the balance and record the mass with units.
3. look up the density of aluminum and record to at least 3 significant figures.

Explanation:

Step1: Define accuracy

Accuracy is how close a measurement is to the true or accepted value.

Step2: Define precision

Precision is how close a set of measurements are to each other.

Step3: Dart - board sketch for high precision and accuracy

The darts are clustered closely around the bull's - eye.

Step4: Dart - board sketch for high precision and poor accuracy

The darts are clustered closely together but far from the bull's - eye.

Step5: Dart - board sketch for poor precision and poor accuracy

The darts are scattered both far from the bull's - eye and from each other.

Step6: Determine significant figures in 83.239 g

All non - zero digits are significant, so there are 5 significant figures.

Step7: Determine significant figures in 100 mL

Trailing zeros without a decimal point may or may not be significant. Here, it is considered 1 significant figure (if no other context). But if it is measured precisely, it could be 3. Assuming no precision indication, 1.

Step8: Determine significant figures in 0.0023 kg

Leading zeros are not significant, so there are 2 significant figures.

Step9: Determine significant figures in 6.3×10⁵ s

The digits in the coefficient (6.3) are significant, so there are 2 significant figures.

Step10: Calculate speed in question 5

Speed \(v=\frac{d}{t}\), where \(d = 59.23\) m and \(t = 13\) s. \(v=\frac{59.23}{13}\approx4.55615\) m/s. Since 13 has 2 significant figures, the answer is \(4.6\) m/s.

Step11: Explain significant figures in question 5

The value 13 s has 2 significant figures. In multiplication and division, the result should have the same number of significant figures as the number with the fewest significant figures in the values used in the calculation.

Step12: Calculate volume of object in question 7

Volume of object \(V=V_{final}-V_{initial}=91.2 - 69.2=22.0\) mL.

Step13: Calculate density of object in question 7

Density \(
ho=\frac{m}{V}\), where \(m = 83.212\) g and \(V = 22.0\) mL. \(
ho=\frac{83.212}{22.0}\approx3.78236\) g/mL. Since 22.0 has 3 significant figures, the density is \(3.78\) g/mL.

Answer:

1. Accuracy: How close a measurement is to the true value.
2. Precision: How close a set of measurements are to each other.
3. High precision and accuracy: Darts clustered around bull's - eye. High precision and poor accuracy: Darts clustered but away from bull's - eye. Poor precision and poor accuracy: Darts scattered.
4. a. 5; b. 1; c. 2; d. 2
5. \(4.6\) m/s
6. The value 13 s has 2 significant figures, so the result of the division has 2 significant figures.
7. Volume of object: 22.0 mL. Density of object: \(3.78\) g/mL