Chemistry IUnit 1B Test Preview

Ray TedderNBC Chemistry Teacher

Unit 1B Test Preview1. The photo on the right is for a section of a pipet containing a liquid. If the pipet was originally filled to the 1.00 mL mark, and liquid has been dispensed to the level indicated in the illustration on the right, how much liquid was dispensed? Show all your work. (C-1.2)Look at the numbering system on the pipet. The smaller numbers are at the top. This means for a device like this, you subtract the starting amount (1.00 mL liquid) from the amount that you read on the pipet.

The liquid level is between 4 mL and 5mL. The smaller markings between the 4 and the 5, a 1 mL amount. Therefore the smaller markings in between the 4 and the 5 must be for increments of a 10th of a mL.

Unit 1B Test Preview1. The photo on the right is for a section of a pipet containing a liquid. If the pipet was originally filled to the 1.00 mL mark, and liquid has been dispensed to the level indicated in the illustration on the right, how much liquid was dispensed? Show all your work. (C-1.2)The bottom of the meniscus almost touches the smaller marking below the 4. This means that the liquid level doesn’t quite come to a 10th of a mL more than 4. Since we have markings for 4.0 and 4.1, we must estimate one more digit between those amounts. This estimate will be one more than a 10th… making it a 100th of a mL. The amount of liquid in the pipet now must be at the 4.09 mL point.

Unit 1B Test Preview1. The photo on the right is for a section of a pipet containing a liquid. If the pipet was originally filled to the 1.00 mL mark, and liquid has been dispensed to the level indicated in the illustration on the right, how much liquid was dispensed? Show all your work. (C-1.2)

Since the liquid is now at 4.09 mL and “was originally at the 1.00 mL mark,” we must subtract the 1.00 mL liquid amount from the 4.09 mL liquid..

4 . 0 9 mL liquid 1 . 0 0 mL liquid

3 . 0 9 mL liquid

Notice how all the digits have been lined up carefully.

Since there are no “empty slots” above any of the digits in the final answer, there is no reason to do any rounding off in this case.

Unit 1B Test Preview2. In what form should a hypothesis be written? In a “cause and effect” or “if/then” form.

Unit 1B Test Preview3. Underline the part of the hypothesis below that identifies the dependent variable.

The part of the experiment that you change is the independent variable.

If the amount of sodium chloride added to 40.0 mL tap water is increased, then the density of the water and salt solution will increase.

The part of the experiment that changes because of the change in the independent variable is the dependent variable.

Unit 1B Test Preview4. Underline the part of the hypothesis below that identifies the independent variable.

The part of the experiment that you change is the independent variable.

If the amount of sodium chloride added to 40.0 mL tap water is increased, then the density of the water and salt solution will increase.

The part of the experiment that changes because of the change in the independent variable is the dependent variable.

Unit 1B Test Preview5. Write the definition of a scientific model.A scientific model is an idealized description of how phenomena occur and how data or events are related.A scientific model is simply an idea that allows us to create explanations of how we think some part of the world works. Models are used to represent a concept or system so that the concept may be more easily understood and predictions can be made.

Unit 1B Test Preview6. There are 110.984 grams of calcium chloride (CaCl2) in one mole of calcium chloride. If you are given 6.25 grams of calcium chloride how many moles would that be? Show all your work.Recognize that the statement, “There are 110.984 grams of calcium chloride (CaCl2) in one mole of calcium chloride,” implies the following equality statement:

110.984 g CaCl2 = 1 mol CaCl2

You can use this equality statement to write conversion units.

Unit 1B Test Preview6. There are 110.984 grams of calcium chloride (CaCl2) in one mole of calcium chloride. If you are given 6.25 grams of calcium chloride how many moles would that be? Show all your work.Recognize that the question, “…given 6.25 grams of calcium chloride how many moles would that be?” implies that 6.25 g CaCl2 is the starting amount. Staring amounts always go over 1:

26.25 g CaCl1

Unit 1B Test Preview6. There are 110.984 grams of calcium chloride (CaCl2) in one mole of calcium chloride. If you are given 6.25 grams of calcium chloride how many moles would that be? Show all your work.Put on the bottom of the conversion unit the side of the equality statement that matches units and species in the starting amount:

2 2

2

6.25 g CaCl 1 mol CaCl1 110.984 g CaCl

110.984 g CaCl2 = 1 mol CaCl2

Unit 1B Test Preview6. There are 110.984 grams of calcium chloride (CaCl2) in one mole of calcium chloride. If you are given 6.25 grams of calcium chloride how many moles would that be? Show all your work.Cancel units and species and solve the problem:

6.25 g 2 CaCl21 mol CaCl

1 110.984 g

2 CaCl

2 20.056314424 mol CaCl 0.0563 mol CaCl .

Don’t forget to round off when appropriate.

Unit 1B Test Preview7. The density of nitrogen (N2) is 1.25 g/L. If you are given a volume of nitrogen that takes up 2.40 L what is the mass of that sample of nitrogen? Show all your work.Recognize that the statement, “The density of nitrogen (N2) is 1.25 g/L,” implies the following equality statement:

1.25 g N2 = 1 L N2

You can use this equality statement to write conversion units.

Unit 1B Test Preview7. The density of nitrogen (N2) is 1.25 g/L. If you are given a volume of nitrogen that takes up 2.40 L what is the mass of that sample of nitrogen? Show all your work.Recognize that the question, “… If you are given a volume of nitrogen that takes up 2.40 L what is the mass of that sample of nitrogen?” implies that 2.40 L N2 is the starting amount. Staring amounts always go over 1:

22.40 L N1

Unit 1B Test Preview7. The density of nitrogen (N2) is 1.25 g/L. If you are given a volume of nitrogen that takes up 2.40 L what is the mass of that sample of nitrogen? Show all your work.Put on the bottom of the conversion unit the side of the equality statement that matches units and species in the starting amount:

2 2

2

2.40 L N 1.25 g N1 1 L N

1.25 g N2 = 1 L N2

Unit 1B Test Preview7. The density of nitrogen (N2) is 1.25 g/L. If you are given a volume of nitrogen that takes up 2.40 L what is the mass of that sample of nitrogen? Show all your work.Cancel units and species and solve the problem:

2.40 L 2 N21.25 g N

1 1 L

2 N

2 23 g N 3.00 g N .

You have to know when an answer needs more digits than your calculator shows and fix the answer.

Unit 1B Test Preview8. Below is a chart in which the amount of table salt (also called sodium chloride or NaCl) was changed in 40.0 mL of tap water. Using the data in the chart, create a table in the space to the right. Then, on the next page, create a graph for this same measurement data. Be sure to include all the things that you have been taught to include on a table and a graph.

Mass of salt dissolved in

40.0 mL water

Densityof the soln

0.00 g 0.995 g/mL2.00 g 1.01 g/mL4.00 g 1.05 g/mL6.00 g 1.09 g/mL8.00 g 1.11 g/mL

10.00 g 1.13 g/mL12.00 g 1.17 g/mL

Unit 1B Test PreviewTable 1. The acceleration of an object compared to the force applied to it. Acceleration

(in m/s2)Force(in N)

0.0 0.05.2 1.99.9 3.8

14.1 6.219.7 8.125.2 9.930.0 12.1

Tables must have:Table numbers.Table descriptions.Column labels with units.

Data cells with numbers can only have numbers (no units of measurement or other letters).

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.00.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

The dependence of force on acceleration

Force (in N)

Acc

eler

atio

n

Figure 1. The figure description should explain to the reader what the data shows and the analysis shows. The type of trend line allows you make analyses. It is your responsibility to develop your own figure description.

Graphs must have:Titles

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.00.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

The dependence of force on acceleration

Force (in N)

Acc

eler

atio

n

Figure 1. The figure description should explain to the reader what the data shows and the analysis shows. The type of trend line allows you make analyses. It is your responsibility to develop your own figure description.

Graphs must have:Axis labels that identify the measurements or calculations plotted on that axis

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.00.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

The dependence of force on acceleration

Force (in N)

Acc

eler

atio

n

Figure 1. The figure description should explain to the reader what the data shows and the analysis shows. The type of trend line allows you make analyses. It is your responsibility to develop your own figure description.

Graphs must have:Axis labels that include units of measurement (usually in parentheses)

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.00.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

The dependence of force on acceleration

Force (in N)

Acc

eler

atio

n

Figure 1. The figure description should explain to the reader what the data shows and the analysis shows. The type of trend line allows you make analyses. It is your responsibility to develop your own figure description.

Graphs must have:Number labels equally spaced on the axes and arranged so the data is spread out as much as possible.

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.00.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

The dependence of force on acceleration

Force (in N)

Acc

eler

atio

n

Figure 1. The figure description should explain to the reader what the data shows and the analysis shows. The type of trend line allows you make analyses. It is your responsibility to develop your own figure description.

Graphs must have:Figure numbers and descriptions.

Mass of salt dissolved in

40.0 mL water

Densityof the soln

0.00 g 0.995 g/mL2.00 g 1.01 g/mL4.00 g 1.05 g/mL6.00 g 1.09 g/mL8.00 g 1.11 g/mL

10.00 g 1.13 g/mL12.00 g 1.17 g/mL

Tables do NOT have:Units of measurement or other letters in cells with numbers.Units of measurement must be moved to the cells with the column label.

The data cells and column label cells must be completely outlined.

Table 1. A comparison of different concentrations of sodium chloride (NaCl) in water and the resulting density of those solutions.

Mass of salt dissolved in 40.0 mL water

(in g) Density of solutions

(in g/mL)0.00 0.9952.00 1.014.00 1.056.00 1.098.00 1.11

10.00 1.1312.00 1.17

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.000.900

0.950

1.000

1.050

1.100

1.150

1.200

f(x) = 0.0145766550530734 x + 0.99183839008295

The effect of sodium chloride concentration on the density of water solutions

Mass of NaCl in 40.0 mL water

Den

sity

of s

olut

ion

(in g

/mL)

Figure 2. This graph illustrates the trend discovered from a comparison of the amount of table salt dissolved in water and the resulting density of those solutions . The pattern of data follows a straight linen with an upward slope

End