2B1 Temperature, Heating, and Thermal Energy

Question 1

Define:

Heat

Answer 1

Energy transferred due to a temperature difference.

Heat is energy in transit from a body of higher temperature to a body of lower temperature.

Question 2

Fill in the blank:

Temperature is a measure of the average ______ energy of particles in a substance.

Answer 2

kinetic

Temperature is a way to describe warmth and coldness using quantitative descriptors.

Question 3

True or False:

Heat and temperature are the same physical quantity.

Answer 3

False

Temperature measures average kinetic energy, while heat refers to energy transferred due to temperature difference.

Question 4

Fill in the blank:

A ______ is an instrument used to measure temperature.

Answer 4

thermometer

Thermometers can be analog (mercury or alcohol-based) or digital, depending on the application.

Question 5

How does temperature affect the speed of particles in a substance?”

Answer 5

Higher temperature corresponds to faster particle motion.

The motion includes translational, rotational, and vibrational movements.

Question 6

Define:

Absolute zero

Answer 6

The lowest possible temperature (0 K) where there is no kinetic energy or motion in a system of particles.

In Celsius, absolute zero is -273.15 degrees. In Fahrenheit, -459.67 degrees.

Question 7

Relate temperature and the state of matter.

Answer 7

Higher temperatures increase particle motion, which can cause changes in state (e.g., solid to liquid).

Phase changes occur when the average kinetic energy overcomes intermolecular forces. Examples include melting (solid to liquid) and evaporation (liquid to gas).

Question 8

Define:

Thermal expansion

Answer 8

Increase in material size as temperature rises.

It occurs because particles move faster and spread apart as they gain energy. Examples include thermometers, where a higher temperature causes the liquid inside to rise, indicating a fever.

Question 9

True or false:

All materials expand at the same rate when heated.

Answer 9

False

The rate of expansion depends on the material’s thermal expansion coefficient. For example, metals expand more than ceramics.

Question 10

What factors affect the heat needed to change a substance’s temperature?

Answer 10

• Temperature difference
• Mass of the substance
• Nature of the substance

These factors determine the heat capacity and specific heat capacity of a substance. Water has high specific heat, meaning it heats up & cools down slowly.

Question 11

Define:

Thermal energy

Answer 11

The total internal energy associated with the motion of the particles (atoms and molecules) in an object or substance.

An example is using thermal energy from a steam engine to move a piston.

Question 12

Why does a swimming pool at the same temperature as a cup of coffee have more thermal energy?

Answer 12

The pool has more thermal energy because it contains a larger number of particles.

Thermal energy depends on both temperature and particle count.

Question 13

Fill in the blank:

Thermal energy is the total energy of particles, while temperature measures their ______ energy.

Answer 13

average kinetic

Thermal energy accounts for both kinetic and potential energy, but temperature only measures average kinetic energy.

Question 14

True or false:

Adding heat always increases a substance’s temperature.

Answer 14

False

Heat can also cause a phase change without increasing temperature (e.g., melting ice). For example, Ice at 0°C absorbs heat but stays at 0°C until fully melted.

Question 15

Define:

Phase transition

Answer 15

The process by which a substance changes from one state of matter (solid, liquid, gas) to another due to energy transfer.

Examples include melting, freezing, vaporization, and condensation, often occurring at specific temperatures and pressures.

Question 16

Explain how heating is related to temperature and thermal energy.

Answer 16

Heating transfers energy to increase a substance’s thermal energy, which may raise its temperature or cause a phase change.

Heating occurs via conduction, convection, or radiation.

Question 17

How are thermal energy, temperature, and particle count related?

Answer 17

Thermal energy increases with higher temperature and more particles.

Larger objects can have more thermal energy even at the same temperature.

Question 18

What does the kinetic molecular theory state about the motion of particles in matter?

Answer 18

All particles of matter are in constant motion and their speed increases with temperature.

This motion explains energy transfer during heating and cooling.

Question 19

Explain how temperature is related to the kinetic energy of particles.

Answer 19

Temperature is directly proportional to the average kinetic energy of the particles in a substance.

Higher temperatures mean faster-moving particles with more kinetic energy, causing more collisions and greater expansion.

Question 20

True or false:

A gas at the same temperature as a solid has particles with the same average kinetic energy.

Answer 20

True

State of matter doesn’t affect average kinetic energy. Temperature determines the average motion of particles.

Question 21

Define:

Specific heat

Answer 21

The amount of thermal energy per unit mass required to increase the temperature by one degree Celsius.

Different substances have different specific heats based on their physical properties.

Question 22

True or false:

Latent heat changes a substance’s temperature during phase transitions.

Answer 22

False

Latent heat is the thermal energy released or absorbed during a phase change at constant temperature.

Question 23

What is the formula for calculating latent heat?

Answer 23

L = Q/m

Where L is latent heat (J/g), Q is heat added or removed (J), and m is mass (g).

Question 24

What is the latent heat of fusion?

Answer 24

It is the energy required to change a substance from a solid to a liquid at constant temperature.

This energy breaks the bonds between particles, enabling the phase transition at occurs at the melting point of a substance.

Question 25

How does latent heat help in **ice pack injury treatment**?

Answer 25

The latent heat of fusion allows ice packs to **absorb heat** as the ice melts, reducing swelling by **extracting heat** from the injured area. ## Footnote The phase change from solid to liquid absorbs heat without increasing the temperature of the ice pack.

Question 26

What is the **unit** of **latent heat**?

Answer 26

Joules per gram (**J/g**) or kilojoules per kilogram (**kJ/kg**). ## Footnote Other units include calories per gram and British thermal units.

Question 27

Explain the difference between **specific heat** and **latent heat**.

Answer 27

Specific heat involves **temperature change**, while latent heat involves **phase changes** without temperature change. ## Footnote Both are measures of heat energy.

Question 28

How does specific heat affect a **material’s ability to retain heat**?

Answer 28

Materials with high specific heat **retain heat longer** and resist temperature change. ## Footnote **Water is an example with high specific heat**, making it useful for thermal regulation.

Question 29

# Define: Heat capacity

Answer 29

The **amount of heat energy required** to raise the temperature of a substance by one unit. ## Footnote It depends on the substance's mass and specific heat.

Question 30

# Fill in the blank: **Heat capacity** is directly proportional to \_\_\_\_\_\_ and inversely proportional to \_\_\_\_\_\_.

Answer 30

mass; temperature change ## Footnote A larger mass requires more energy for the same temperature change, while a greater temperature change lowers heat capacity for a fixed energy input.

Question 31

Which common substance has the **highest specific heat capacity**?

Answer 31

**Water** (4184 J/kg-K) ## Footnote Water's high specific heat capacity allows it to absorb a significant amount of heat, making it useful in various applications.

Question 32

What is the **SI unit** of **heat capacity**?

Answer 32

Joules per Kelvin (J/K). ## Footnote This unit represents the ratio of heat supplied to the corresponding temperature change. The equation is C = Q / ΔT, or, heat divided by the temperature change.

Question 33

Why is **water** used as a **coolant** in car engines?

Answer 33

Because of its **high specific heat capacity**, water can absorb and store large amounts of heat without a significant rise in temperature. ## Footnote This helps regulate engine temperature and prevent overheating.

Question 34

# Fill in the blank: **Thermal energy storage** systems use materials with high \_\_\_\_\_\_ to store and release heat efficiently.

Answer 34

specific heat or latent heat ## Footnote Materials like molten salts or phase change materials (PCMs) are used in solar power plants and building insulation.

Question 35

What are the three modes of **heat transfer**?

Answer 35

1. Conduction 2. Convection 3. Radiation ## Footnote Each mode describes a different mechanism by which heat can move through or out of a system.

Question 36

# Define: Conduction

Answer 36

Mode of **energy transfer** that occurs by **direct contact** between particles. ## Footnote It occurs in solids, where particles vibrate to transfer energy. For instance, when you are walking on hot sand, the heat energy is conducted through direct contact with your feet.

Question 37

# Fill in the blank: **Convection** transfers heat through the movement of particles within a \_\_\_\_\_\_.

Answer 37

fluid ## Footnote Warm fluid rises while cooler fluid sinks, creating convection currents.

Question 38

How does **convection** work in boiling water?

Answer 38

**Hot** water **rises** while **cold** water **sinks**, creating a **cycle** that transfers heat throughout the pot. ## Footnote This process is known as thermal expansion.

Question 39

# True or false: **Radiation** requires a medium to transfer heat.

Answer 39

False ## Footnote Radiation transfers heat through electromagnetic waves, even in a vacuum. An example is the sun's radiation warming the Earth.

Question 40

How does radiation help **solar panels** generate electricity?

Answer 40

Solar panels absorb radiant energy from the sun and convert it into electrical energy using **photovoltaic cells**. ## Footnote Radiation is the transfer of energy through electromagnetic waves, which solar panels efficiently harness.

Question 41

What are everyday examples of **conduction**, **convection**, and **radiation**?

Answer 41

* Conduction: Touching a hot pan. * Convection: Boiling water. * Radiation: Feeling warmth from sunlight. ## Footnote All three mechanisms transfer thermal energy but differ in process and medium.

Question 42

What is the **difference** between *conduction* and *convection*?

Answer 42

* **Conduction** transfers heat through contact. * **Convection** uses the movement of fluids. ## Footnote Conduction is more common in solids and liquids.

Question 43

What **units** are commonly used to **measure temperature**?

Answer 43

* Celsius * Fahrenheit * Kelvin ## Footnote Kelvin is used in scientific contexts, Celsius is common worldwide, and Fahrenheit is primarily used in the United States.

Question 44

# Define: **Kelvin** temperature scale

Answer 44

Kelvin measures temperature starting from **absolute zero**, where particle motion stops. ## Footnote It is commonly used in scientific calculations.

Question 45

What is the lowest temperature possible on the **Kelvin** scale?

Answer 45

0 K ## Footnote This temperature is known as absolute zero, where there is no molecular movement.

Question 46

# Fill in the blank: 0°C corresponds to \_\_\_\_\_\_ **Kelvin**.

Answer 46

273.15 ## Footnote Kelvin = Celsius + 273.15

Question 47

# True or false: The **Fahrenheit** scale is widely used in scientific contexts.

Answer 47

False ## Footnote Fahrenheit is used mainly in the U.S., while Celsius and Kelvin dominate in science.

Question 48

Explain the **difference** between the *Celsius* and *Fahrenheit* scales.

Answer 48

* The **Celsius** scale is based on water’s freezing point (0°C) and boiling point (100°C). * The **Fahrenheit** scale uses 32°F and 212°F for the same. ## Footnote They are both relative scales, unlike Kelvin.

Question 49

What are the **freezing and boiling points** of water in Celsius?

Answer 49

* Water's freezing point: 0°C * Water's boiling point: 100°C ## Footnote These values are standard measurements at normal atmospheric pressure.

Question 50

Relate the **temperature scales** to real-world applications.

Answer 50

* Celsius: Meteorology. * Fahrenheit: U.S. weather reports. * Kelvin: Scientific research. ## Footnote Each scale suits specific contexts and practices.