ACHM115 Exam 1 Topics

Ch.1:states of matter + properties and changes

100

What is a heterogenous mixture? Provide an example.

• A mixture that has a varied composition from point to point. Ex: Apple

200

What is an extensive property?

• Property that depends on the amount of matter present. 

300

A student in your class says that water boiling in a pot is experiencing a chemical change because a liquid is changing into a gas. Is this true or false?

False. Chemical changes only occur when one substance before the change transforms into another. Water turning into steam is simply a change in its state of matter. It is still water whether in its liquid or gas form.

400

Jess visits a jeweler and decides to purchase a pair of 14-karat gold earrings. What type of matter is 14-karat gold?

Homogenous mixture. 14-karat gold is not pure gold and is often made by combining gold with different types of other metals such as copper, silver, nickel, zinc, and palladium. These additional metals can have varying compositions. 

500

A student measures a piece of an unknown metal and records:

• Mass: 250 g
• Volume: 31.25 mL
• Density: 8.00 g/mL
• Melting point: 1,083°C
• Reacts with oxygen to form a green compound.

For each observation, determine what type of property it is. 

From top to bottom: extensive, extensive, intensive, physical, and chemical. 

Think: in-tensive = in-herent. A property is inherent to the substance. It does not change no matter how much you have. 

Ch.1: significant figures

100

How many significant figures in the following numbers:

- 400

- 400.

- 0.0000100110

- 3.1005 x 10⁵

From top to bottom: 1, 3, 6, and 5

200

Round the following two numbers to 3 significant figures in scientific notation:

- 0.004007

- 34002.001 

From top to bottom: 

- 4.01 x 10^-3

- 3.40 x 10⁴

300

Solve the following problem to the correct number of significant figures:

0.1156 + 14.1

0.1156 + 14.1 = 14.2156 -> 14.2

400

Solve the following problem to the correct number of significant figures (no scientific notation):

0.001170 x 133000

0.001170 x 133000 = 155.61 -> 156

500

Solve the following problem to the correct significant figures:

(10.0110 + 18.233)*1.506/1.22

34.9

Ch.1: dimensional analysis

100

What is dimensional analysis?

Dimensional analysis is a strategy used to ensure that solutions have the correct units when converting from one quantity to another. 

200

Convert 4.7 feet into inches. Ensure correct significant figures.

4.7 ft*(12 in/1 ft) = 56.4 inches -> 56 inches

300

Convert 68.9 gallons into liters if 1 gallon = 3.78541 liters. Ensure correct significant figures.

68.9 gal*(3.78541 L/1 gal) = 260.814749 -> 261 L

400

Convert 4571 seconds into hours. Ensure correct significant figures.

4571 s*(1 min/60 s)*(1 hr/60 min) = 1.26972 -> 1.270 hr

500

Convert a ball moving at 15.0 m/s into mi/hr. 1 km = 1000 m. 1 km = 0.621371 miles. Ensure correct significant figures.

15.0 m/s*(1 km/1000 m)*(0.621371 mi/1 km)*(60 s/1 min)*(60 min/1 hr) = 33.554034 -> 33.6 mi/hr

Ch.2: atomic theory, atomic structure, elements, and periodic table

100

What is the law of constant composition? 

The relative kinds and numbers of atoms are constant for a given compound. For example, water will always be a hydrogen-to-oxygen ratio of 2:1. 

200

What did the gold foil experiment discover about the atom?

Atoms are mainly empty space with a solid, center nucleus. 

300

What determines an elements position on the periodic table?

The number of protons it has.

400

What is group 7A called on the periodic table?

Group 7A or 17 are the halogens.

500

What is a metalloid and where do they generally reside on the periodic table? 

Metalloids are elements that have properties of both metals and non-metals and are placed by the staircase that separates metals from non-metals. The metalloids include: B, Si, Ge, As, Sb, and Te. 

Ch.2: Isotopes and average atomic mass

100

What is an isotope?

Atoms of the same element with different masses due to different numbers of neutrons. 

200

What is average atomic mass?

Average atomic mass is the mass of an element calculated from the isotopes of an element weighted by their relative abundances. 

300

True or false: All isotopes of any given element occur with the same abundance on Earth. 

False. Some isotopes are more abundant than others due to many reasons. One reason is due to stability. Unstable isotopes break down too fast to significantly contribute to their abundance. 

400

Element X has two known isotopes. ²⁰X has an abundance of 71.15 and a mass of 14.5 amu. ²¹X has an abundance of 28.85 and a mass of 15.1 amu. Calculate the average atomic mass. Ensure proper significant figures. 

71.15 -> 0.7115%

28.85 -> 0.2885%

(14.5)(0.7115) + (15.1)(0.2885) = 14.6731 -> 14.7 amu

(Both given masses are 3 sig figs with 1 dp)

500

Element Y has three known isotopes. ¹¹Y has an abundance of 31.45 with a mass of 89.1 amu. ¹⁴Y has an abundance of 1.75 with a mass of 90.0 amu. ¹⁵Y has an abundance of 66.80 with a mass of 92.3 amu. Calculate the average atomic mass. Ensure proper significant figures.

31.45 -> 0.3145

1.75 -> 0.0175

66.80 -> 0.6680

(89.1)(0.3145) + (90.0)(0.0175) + (92.3)(0.6680) = 91.25335 -> 91.3 amu

(All given masses are 3 sig figs with 1 dp)