Question

unit 1- matter and the mole
unit 1 practice test
directions: differentiate the following terms related to the scientific method.

1. dependent variable vs independent variable
2. hypothesis vs theory

directions: solve the following problems. show all work! be sure to include the correct unit with your final answer.

1. what is the density of a solid that has a volume of 4 cm³ and a mass of 6 grams?
2. to determine the density of an irregularly shaped object, a student immersed it in 10.0 ml of water, causing the water level to rise to 13.2 ml. if the object had a mass of 7.01 g, what is the density of the object?
3. a sample of a metal alloy has a density of 4.12 g/cm³ and occupies a volume of 31.2 cm³. what is its mass?

directions: for each sample of matter below, correctly classify it as a pure substance or a mixture.

1. trail mix
2. helium gas
3. distilled water

directions: for each, correctly classify as homogeneous or heterogeneous mixture.

1. vegetable soup
2. gatorade
3. orange juice, with pulp

directions—convert between particles and moles

1. 24 atoms of sodium = ____ moles of sodium atoms
2. 5 molecules of chlorine gas = ____ moles of chlorine molecules
3. 900 atoms of silver = ____ moles of silver atoms
4. 2.89 x 10²³ molecules of ammonia = ____ moles of ammonia molecules
5. 15 moles of arsenic atoms = ____ atoms of arsenic
6. 4.00 x 10³ moles of barium atoms = ____ atoms of barium

multiple choice practice

1. the amount of mass per unit volume refers to the

a. density
b. specific weight
c. volume
d. weight

1. a substance that can be further simplified may be either

a. an element or a compound
b. an element or a mixture
c. a mixture or a compound
d. a mixture or an atom

1. a substance composed of two or more elements chemically united is called

a. an isotope
b. a compound
c. an element
d. a mixture

1. a substance that cannot be further decomposed by ordinary chemical means is

a. water
b. air
c. sugar
d. silver

Explanation:

Step1: Recall density formula

The density formula is $
ho=\frac{m}{V}$, where $
ho$ is density, $m$ is mass, and $V$ is volume.

Step2: Solve problem 3

Given $m = 6$ g and $V=4$ cm³. Substitute into the formula: $
ho=\frac{6\ g}{4\ cm^{3}} = 1.5$ g/cm³.

Step3: Solve problem 4

First, find the volume of the object. The volume of the object is the change in water - level volume. $V=13.2\ mL - 10.0\ mL=3.2\ mL = 3.2$ cm³ (since 1 mL = 1 cm³). Given $m = 7.01$ g. Then $
ho=\frac{7.01\ g}{3.2\ cm^{3}}\approx2.19$ g/cm³.

Step4: Solve problem 5

Given $
ho = 4.12$ g/cm³ and $V = 31.2$ cm³. Using the formula $m=
ho V$, we have $m=4.12\ g/cm^{3}\times31.2\ cm^{3}=128.544$ g.

Step5: Classify matter in problem 6

Trail - mix is a mixture because it contains different substances (such as nuts, raisins, etc.) that are not chemically combined.

Step6: Classify matter in problem 7

Helium gas is a pure substance because it consists of only helium atoms.

Step7: Classify matter in problem 8

Distilled water is a pure substance. It is a compound (H₂O) and is homogeneous at the molecular level.

Step8: Classify mixtures in problem 9

Vegetable soup is a heterogeneous mixture because it has visible different components (pieces of vegetables, broth, etc.).

Step9: Classify mixtures in problem 10

Gatorade is a homogeneous mixture as it is a uniform solution.

Step10: Classify mixtures in problem 11

Orange juice with pulp is a heterogeneous mixture because of the visible pulp.

Step11: Convert particles to moles in problem 12

Use the conversion factor $1$ mole = $6.022\times10^{23}$ particles. For 24 atoms of sodium, $n=\frac{24}{6.022\times10^{23}}\approx3.99\times10^{-23}$ moles.

Step12: Convert particles to moles in problem 13

For 5 molecules of chlorine gas, $n=\frac{5}{6.022\times10^{23}}\approx8.30\times10^{-24}$ moles.

Step13: Convert particles to moles in problem 14

For 900 atoms of silver, $n=\frac{900}{6.022\times10^{23}}\approx1.5\times10^{-21}$ moles.

Step14: Convert particles to moles in problem 15

For $2.89\times10^{23}$ molecules of ammonia, $n=\frac{2.89\times10^{23}}{6.022\times10^{23}}\approx0.48$ moles.

Step15: Convert moles to atoms in problem 16

Using the conversion factor $1$ mole = $6.022\times10^{23}$ atoms. For 15 moles of arsenic atoms, $N = 15\times6.022\times10^{23}=9.033\times10^{24}$ atoms.

Step16: Convert moles to atoms in problem 17

For $4.00\times10^{3}$ moles of barium atoms, $N=4.00\times10^{3}\times6.022\times10^{23}=2.4088\times10^{27}$ atoms.

Step17: Answer multiple - choice problem 18

The amount of mass per unit volume refers to density. So the answer is a. Density.

Step18: Answer multiple - choice problem 19

A substance that can be further simplified may be either a mixture or a compound. So the answer is c. A mixture or a compound.

Step19: Answer multiple - choice problem 20

A substance composed of two or more elements chemically united is called a compound. So the answer is b. A compound.

Step20: Answer multiple - choice problem 21

A substance that cannot be further decomposed by ordinary chemical means is an element. Silver is an element. So the answer is d. Silver.

Answer:

1. 1.5 g/cm³
2. 2.19 g/cm³
3. 128.544 g
4. Mixture
5. Pure substance
6. Pure substance
7. Heterogeneous mixture
8. Homogeneous mixture
9. Heterogeneous mixture
10. $3.99\times10^{-23}$ moles
11. $8.30\times10^{-24}$ moles
12. $1.5\times10^{-21}$ moles
13. 0.48 moles
14. $9.033\times10^{24}$ atoms
15. $2.4088\times10^{27}$ atoms
16. a. Density
17. c. A mixture or a compound
18. b. A compound
19. d. Silver