Chemistry Test - Unit 1 This test is worth 60 points. Choose problems from each section worth a tofal of 60 points. Problem point values are shown in bold at the end of the question. Harder problems are worth more points. Circle the problem number for those problems which you want graded. Show all work for each problem on the test itself. Draw a box around your final answer. Make sure that your answers contain the proper units and signjiicantfigures.

I. Knowledge 1.

Explain why the significant figure convention is used by scientists. (3) To make sure the limits on the precision of your measurement are understood when communicating the number.

3. D e h e and explain the difference between precision and accuracy. (3) Precision describes how close a set of numbers are to each other (closer = more precise), while accuracy refers to how close a number is to a known or compared value. 4.

Describe the difference in technique for reading volume in a glass graduated cylinder versus a plastic cylinder. (3) A glass graduated cylinder has a meniseus, the upsidedown smile shape that results from adhesion to the glass. You read this from a horizontal line across the bottom of the smile. Plastic graduated cylinders don't have ameniscus, but you still read from the bottom of the line.

5, Identify the three pieces of lab equipment shown at the front of the room. (3)

11. Application

1. List the number of significant figures in the following examples: (3) (a) 157.0

@)0.005470

4

4

2. Calculate the following, observing significant figure rules. (6) (a) 35 + 18.6 =

54

(b) 196 x .00507 = 1.12

(c) 0.00670 + 3.5 =

.a019

(d) 1 .OO

- 2.739 = -1.74

(c) 10005.050

8

3.

Calculate the following, observing significant figure mles. (3) (a) (1.2345 x 10') x 0.00009 = 10000 @) (7.880 x 1 0 3 + (3.2 x 10") = 25

4.

Convert the following using dimensional analysis: (a) 35 km to feet (3) 35 k m x

5.

(=)lOOOm x (-iI;O;-)O m x (=1)inch

x (=)

I foot

= 110,000 feet

The density of gold is recorded as 19.3 g/cm3. A laboratory measures a sample of pure gold to have a density of 18.4 g/mL. Calculate the percent error associated with this measurement. (3)

111. Synthesis

1. An engineer measures the length and width of a piece of metal to be 4.0 in and 5.0 in respectively. His machine shop fashions a piece of metal with a total area of 20.0 inz. Is the piece of metal the correct size? Explain your reasoning why the piece is the correct size or not. (6) The answer is more precise than the measurements, meaning that it is not possible to measure the area of the piece as precisely as it is stated. Thus we can't say that it really is 20.0 in2.

2.

Describe the process by which yon would determine the mass of a certain volume of liquid. You have a balance, a beaker, a graduated cylinder, and a dropper. (3) One method would be to tare a graduated cylinder on a balance and then add liquid to the cylinder using the dropper until the desired volume is read, then read the mass. There are other methods.

3.

Helium gas has a density of 0.126 g/crn'. Calculate the weight in pounds of 10.0 ft3of helium. (9) 12

loft3 x (- 1fwt 4.

( e l 3 (9 (x) ) 78.6 lb. =

1 inch

I""

454 g

Mr. Grunden's I s m gets 30 miles per gallon of gas. If the price of regular unleaded is $1.49/gallon, how far could Mr. Gmnden drive on $15.00? (6)

$15.00

x (-l :1a:9m)

3 0 miles x (-)=

302.0 miles

5. When Mr. Gnmden worked at Subway, he frequently presided over very busy lunches and had to order produce to prepare for them. Given that 24 heads of lettuce come in a case of lettuce, 5 ounces of lettuce come on a footlong sub, a head of lettuce weighs 0.5 pounds, and a busy lunch could produce 250 footloog subs, how many cases of lettuce should Mr. Grunden order for tomorrow's lunch? (9)

I. Knowledge 1.

Explain why the significant figure convention is used by scientists. (3) To make sure the limits on the precision of your measurement are understood when communicating the number.

3. D e h e and explain the difference between precision and accuracy. (3) Precision describes how close a set of numbers are to each other (closer = more precise), while accuracy refers to how close a number is to a known or compared value. 4.

Describe the difference in technique for reading volume in a glass graduated cylinder versus a plastic cylinder. (3) A glass graduated cylinder has a meniseus, the upsidedown smile shape that results from adhesion to the glass. You read this from a horizontal line across the bottom of the smile. Plastic graduated cylinders don't have ameniscus, but you still read from the bottom of the line.

5, Identify the three pieces of lab equipment shown at the front of the room. (3)

11. Application

1. List the number of significant figures in the following examples: (3) (a) 157.0

@)0.005470

4

4

2. Calculate the following, observing significant figure rules. (6) (a) 35 + 18.6 =

54

(b) 196 x .00507 = 1.12

(c) 0.00670 + 3.5 =

.a019

(d) 1 .OO

- 2.739 = -1.74

(c) 10005.050

8

3.

Calculate the following, observing significant figure mles. (3) (a) (1.2345 x 10') x 0.00009 = 10000 @) (7.880 x 1 0 3 + (3.2 x 10") = 25

4.

Convert the following using dimensional analysis: (a) 35 km to feet (3) 35 k m x

5.

(=)lOOOm x (-iI;O;-)O m x (=1)inch

x (=)

I foot

= 110,000 feet

The density of gold is recorded as 19.3 g/cm3. A laboratory measures a sample of pure gold to have a density of 18.4 g/mL. Calculate the percent error associated with this measurement. (3)

111. Synthesis

1. An engineer measures the length and width of a piece of metal to be 4.0 in and 5.0 in respectively. His machine shop fashions a piece of metal with a total area of 20.0 inz. Is the piece of metal the correct size? Explain your reasoning why the piece is the correct size or not. (6) The answer is more precise than the measurements, meaning that it is not possible to measure the area of the piece as precisely as it is stated. Thus we can't say that it really is 20.0 in2.

2.

Describe the process by which yon would determine the mass of a certain volume of liquid. You have a balance, a beaker, a graduated cylinder, and a dropper. (3) One method would be to tare a graduated cylinder on a balance and then add liquid to the cylinder using the dropper until the desired volume is read, then read the mass. There are other methods.

3.

Helium gas has a density of 0.126 g/crn'. Calculate the weight in pounds of 10.0 ft3of helium. (9) 12

loft3 x (- 1fwt 4.

( e l 3 (9 (x) ) 78.6 lb. =

1 inch

I""

454 g

Mr. Grunden's I s m gets 30 miles per gallon of gas. If the price of regular unleaded is $1.49/gallon, how far could Mr. Gmnden drive on $15.00? (6)

$15.00

x (-l :1a:9m)

3 0 miles x (-)=

302.0 miles

5. When Mr. Gnmden worked at Subway, he frequently presided over very busy lunches and had to order produce to prepare for them. Given that 24 heads of lettuce come in a case of lettuce, 5 ounces of lettuce come on a footlong sub, a head of lettuce weighs 0.5 pounds, and a busy lunch could produce 250 footloog subs, how many cases of lettuce should Mr. Grunden order for tomorrow's lunch? (9)