Q: A student heats 50.0 g of water from 20.0 °C to 80.0 °C. How much heat (in joules) is absorbed by the water? (Specific heat of water = $4.184 \ \mathrm{J/g\ ^\circ C}$)

$q = m \times SH \times \Delta T = 50.0 \times 4.184 \times (80.0 - 20.0) = 12,552 \ \mathrm{J}$

Q: A sample of lead with a mass of 35.6 g absorbs 57.0 J of heat, causing its temperature to rise by 12.5 °C. What is the specific heat of lead in J/g°C?

$SH = \frac{q}{m \times \Delta T} = \frac{57.0}{35.6 \times 12.5} = 0.128 \ \mathrm{J/g\ ^\circ C}$

Q: A cracker contains 19 g of carbohydrate, 4 g of fat, and 2 g of protein. Using the energy values 4 kcal/g for carbohydrate, 9 kcal/g for fat, and 4 kcal/g for protein, what is the total energy in kilocalories?

$19 \times 4 + 4 \times 9 + 2 \times 4 = 76 + 36 + 8 = 120 \ \mathrm{kcal}$ (rounded to the tens place: 130 kcal)

Q: A patient is cooled from 38.5 °C to 33.2 °C during surgery. If the blood volume is 5500 mL (density = 1.0 g/mL, specific heat = $4.184 \ \mathrm{J/g\ ^\circ C}$), how much heat is lost in kJ?

$q = m \times SH \times \Delta T = 5500 \times 4.184 \times (33.2 - 38.5) = 5500 \times 4.184 \times (-5.3) = -122,000 \ \mathrm{J} = -122 \ \mathrm{kJ}$

Question 1

Which of the following best describes the difference between a compound and a mixture?

Accepted Answer

A compound contains two or more elements chemically combined in a fixed ratio, while a mixture contains two or more substances physically combined in variable proportions.

Question 2

A student heats 50.0 g of water from 20.0 °C to 80.0 °C. How much heat (in joules) is absorbed by the water? (Specific heat of water = $4.184 \ \mathrm{J/g\ ^\circ C}$)

Accepted Answer

$q = m 	imes SH 	imes \Delta T = 50.0 	imes 4.184 	imes (80.0 - 20.0) = 12,552 \ \mathrm{J}$

Question 3

Which of the following is an example of a homogeneous mixture?

Accepted Answer

Brass (an alloy of copper and zinc)

Question 4

A patient’s body temperature is measured at 39.0 °C. What is this temperature in Kelvin?

Accepted Answer

$T_K = T_C + 273 = 39.0 + 273 = 312 \ \mathrm{K}$

Question 5

Which of the following changes is a chemical change?

Accepted Answer

Iron rusting in an old car

Question 6

A defibrillator delivers 360 J of energy. How many calories is this? ($1 \ \mathrm{cal} = 4.184 \ \mathrm{J}$)

Accepted Answer

$\frac{360}{4.184} = 86.1 \ \mathrm{cal}$

Question 7

Which of the following best describes a physical property?

Accepted Answer

Copper is a shiny metal.

Question 8

A sample of lead with a mass of 35.6 g absorbs 57.0 J of heat, causing its temperature to rise by 12.5 °C. What is the specific heat of lead in J/g°C?

Accepted Answer

$SH = \frac{q}{m 	imes \Delta T} = \frac{57.0}{35.6 	imes 12.5} = 0.128 \ \mathrm{J/g\ ^\circ C}$

Question 9

Which of the following is NOT a pure substance?

Accepted Answer

Air

Question 10

A cracker contains 19 g of carbohydrate, 4 g of fat, and 2 g of protein. Using the energy values 4 kcal/g for carbohydrate, 9 kcal/g for fat, and 4 kcal/g for protein, what is the total energy in kilocalories?

Accepted Answer

$19 	imes 4 + 4 	imes 9 + 2 	imes 4 = 76 + 36 + 8 = 120 \ \mathrm{kcal}$ (rounded to the tens place: 130 kcal)

Question 11

Which of the following best describes the energy transformation in a hydroelectric dam?

Accepted Answer

Potential energy of water is converted to kinetic energy as water flows over the dam.

Question 12

Which of the following is a heterogeneous mixture?

Accepted Answer

Water and copper

Question 13

A patient is cooled from 38.5 °C to 33.2 °C during surgery. If the blood volume is 5500 mL (density = 1.0 g/mL, specific heat = $4.184 \ \mathrm{J/g\ ^\circ C}$), how much heat is lost in kJ?

Accepted Answer

$q = m 	imes SH 	imes \Delta T = 5500 	imes 4.184 	imes (33.2 - 38.5) = 5500 	imes 4.184 	imes (-5.3) = -122,000 \ \mathrm{J} = -122 \ \mathrm{kJ}$

Question 14

Which of the following is a chemical property?

Accepted Answer

A silver knife can tarnish.

Question 15

Convert 113 °F (used in thermotherapy) to degrees Celsius using the correct formula.

Accepted Answer

$T_C = \frac{113 - 32}{1.8} = 45.0 \ ^\circ C$

Question 16

Which of the following is NOT a physical change?

Accepted Answer

Burning a candle

Question 17

Which of the following statements about the Kelvin temperature scale is correct?

Accepted Answer

The Kelvin scale starts at absolute zero, which is $0 \ \mathrm{K}$ or $-273 \ ^\circ \mathrm{C}$.

Chapter 3: Matter and Energy – Classification, Properties, Temperature, and Energy Calculations

Study Guide - Practice Questions

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