Midterm 1 Measurements/Matter & Energy

Which change results in the formation of different substances?

• burning of propane

• melting of NaCl(s)

• deposition of CO₂(g)

• solidification of water

Answer explanation

Burning of propane involves a chemical reaction that produces new substances (carbon dioxide and water), while the other options are physical changes that do not create different substances.

Tags

NGSS.HS-PS1-4

NGSS.HS-PS1-2

Given the balanced equation representing a reaction: N₂ + energy → N + N Which statement describes this reaction?

• Bonds are broken, and the reaction is endothermic.

• Bonds are broken, and the reaction is exothermic.

• Bonds are formed, and the reaction is endothermic.

• Bonds are formed, and the reaction is exothermic.

Answer explanation

In the reaction N2 + energy → N + N, energy is required to break the N≡N bond, indicating that bonds are broken. Since energy is absorbed, the reaction is endothermic.

Tags

NGSS.HS-PS1-4

Given the diagram representing a process being used to separate the colored dyes in food coloring: Which process is represented by this diagram?

• chromatography

• electrolysis

• distillation

• titration

Answer explanation

The diagram represents chromatography, a technique used to separate mixtures into their individual components, such as colored dyes in food coloring. Electrolysis, distillation, and titration are different processes not applicable here.

Which quantity of heat is equal to 200. joules?

• 20.0 kJ

• 2.00 kJ

• 0.200 kJ

• 0.0200 kJ

Answer explanation

To convert joules to kilojoules, divide by 1000. Thus, 200 joules = 200 / 1000 = 0.200 kJ. Therefore, the correct answer is 0.200 kJ.

Tags

NGSS.HS-PS3-4

A student measures the mass and volume of a piece of aluminum. The measurements are 25.6 grams and 9.1 cubic centimeters. The student calculates the density of the aluminum. What is the percent error of the student’s calculated density of aluminum?

• 1%

• 2%

• 3%

• 4%

Answer explanation

To find the density, use the formula density = mass/volume. The student's density is 25.6 g / 9.1 cm³ = 2.81 g/cm³. The accepted density of aluminum is 2.70 g/cm³. Percent error = |(2.81 - 2.70) / 2.70| * 100 = 1%. Thus, the correct answer is 1%.

Which Kelvin temperature is equivalent to –24°C?

• 226 K

• 249 K

• 273 K

• 297 K

Answer explanation

To convert Celsius to Kelvin, add 273.15. For -24°C: -24 + 273.15 = 249.15 K, which rounds to 249 K. Thus, the correct answer is 249 K.

A student calculates the density of an unknown solid. The mass is 10.04 grams, and the volume is 8.21 cubic centimeters. How many significant figures should appear in the final answer?

• 1

• 2

• 3

• 4

Answer explanation

The mass (10.04 g) has 4 significant figures, and the volume (8.21 cm³) has 3 significant figures. The final density calculation should be reported with the least number of significant figures, which is 3.

The diagram represents a Celsius thermometer recording a certain temperature. What is the correct reading of the thermometer?

• 5°C

• 4.3°C

• 0.3°C

• 4°C

Answer explanation

The thermometer shows a level between 4°C and 5°C. By closely examining the scale, the reading is approximately 4.3°C, making it the correct choice among the options provided.

The diagram represents a portion of a 100-milliliter graduated cylinder. What is the reading of the meniscus?

• 35.0 mL

• 36.0 mL

• 44.0 mL

• 45.0 mL

Answer explanation

The meniscus is the curve seen at the surface of a liquid in a graduated cylinder. It should be read at the bottom of the curve. In this case, the bottom of the meniscus aligns with the 35.0 mL mark, making it the correct reading.

Which mass measurement contains four significant figures?

• 0.086 g

• 0.431 g

• 1003 g

• 3870 g

Answer explanation

The measurement 1003 g contains four significant figures, as all non-zero digits are significant. In contrast, 0.086 g has only two significant figures, 0.431 g has three, and 3870 g has three significant figures.