What'S The Difference Between Specific Heat And Temperature?

Table of Contents

Introduce Specific Heat and Temperature

Specific heat and temperature are two important thermodynamic properties used to study heat transfer and the energy content of materials. While related, they refer to different characteristics of matter.

Specific heat is defined as the amount of heat energy required to raise the temperature of 1 gram of a substance by 1°C. It is measured in J/g°C or cal/g°C. Substances with higher specific heats require more heat to increase their temperature.

Temperature refers to the thermal state of matter and the kinetic energy of molecules. It is measured on temperature scales like Celsius, Fahrenheit, or Kelvin. Temperature changes when heat is added or removed from a system.

While specific heat depends on the substance, temperature does not. Specific heat is an intensive property, while temperature is an extensive property. Understanding the difference between the two is key for thermodynamic calculations and analysis.

Units of Measurement

Specific heat is measured in joules per gram degree Celsius (J/g°C). This unit quantifies the amount of heat energy required to raise the temperature of one gram of a substance by one degree Celsius. The SI unit for specific heat is J/(kg⋅K) but J/(g⋅°C) is commonly used.

Temperature is measured in degrees on one of three main scales: Celsius, Fahrenheit, and Kelvin. The Celsius scale uses degrees Celsius (°C) with 0° representing the freezing point of water and 100° the boiling point at standard atmospheric pressure. The Fahrenheit scale uses degrees Fahrenheit (°F) with 32° representing the freezing point and 212° the boiling point of water at standard atmospheric pressure. The Kelvin scale uses the kelvin (K) unit with 0 K representing absolute zero, the coldest theoretical temperature where molecular motion stops.

Molecular Explanation

Specific heat relates to the amount of energy required to raise the temperature of a substance. This is determined by the molecular structure and bonding within the material. Substances like metals have free-moving electrons that can absorb thermal energy easily, resulting in a high specific heat capacity. Other materials like gases have individual molecules that move freely and can gain kinetic energy rapidly when heated, also causing a high specific heat.

In contrast, temperature measures the average kinetic energy of molecular motion in a substance. As more heat is added to a material, the molecules vibrate and rotate faster, corresponding to a rise in temperature. The temperature indicates the total internal energy within the substance, while the specific heat determines how much additional energy is needed to increase the temperature by one degree.

Factors Affecting Specific Heat

The specific heat of a substance depends on two key factors: phase and chemical composition.

Phase refers to whether a substance is a solid, liquid, or gas. The atoms or molecules in a substance have different degrees of freedom to move based on the phase. Solids have the lowest specific heat capacity because the atoms or molecules are tightly locked into position and cannot move freely. Liquids have a higher specific heat capacity than solids because the molecules have more freedom to translate or move with respect to each other. Gases have the highest specific heat capacity because in addition to translational movement, the molecules can rotate and vibrate – which gives them more ways to absorb energy.

Chemical composition also affects specific heat because some atom and molecule combinations can absorb and store more energy than others for a given temperature change. The specific heat correlates with the number and types of bonds between atoms in the molecules. Compounds with more complex molecular structures tend to have higher specific heats than simpler compounds because they have more vibrational modes that can be excited by absorbing thermal energy.

Calculating Specific Heat

The specific heat of a substance can be calculated using the following formula:

Specific heat (c) = Energy (Q) / (Mass (m) x Temperature change (ΔT))

Where:

c = Specific heat capacity (J/g°C or J/kg°C)

Q = Energy/heat added or removed (Joules)
m = Mass of the substance (g or kg)
ΔT = Change in temperature (°C or K)

Here is an example specific heat calculation:

If a 2 kg iron block absorbs 1,000 J of energy and its temperature increases by 10°C, what is the specific heat of iron?

Using the formula:

c = Q / (m x ΔT)

c = 1,000 J / (2 kg x 10°C)

c = 500 J / (2 x 10)

c = 25 J/kg°C

Therefore, the specific heat of iron is 25 J/kg°C.

Specific Heat vs Heat Capacity

While related, there is an important distinction between specific heat and heat capacity. Heat capacity refers to the amount of heat energy required to raise the temperature of an entire system by 1 degree. It depends on both the mass of the substance and its specific heat. Heat capacity is an extensive property, meaning it scales with the size or amount of material.

Specific heat refers to the amount of heat required to change the temperature of 1 unit mass of a substance by 1 degree. It is an intensive property, meaning it does not depend on the amount of material present. Specific heat is a characteristic of the material or substance itself.

For example, the heat capacity of 5 kg of iron is much greater than 1 kg of iron. But both samples have the same specific heat, since they are the same material. Specific heat allows us to compare how easily different materials can change temperature when energy is added or removed.

Table of Specific Heats

Below are the specific heat capacities of some common substances:

Substance	Specific Heat Capacity (J/g°C)
Water	4.18
Ethanol	2.44
Aluminum	0.91
Iron	0.45
Mercury	0.14

This table provides the specific heat capacity values for some common substances like water, metals, and liquids. The values are given in joules per gram per degree Celsius (J/g°C). Having a reference table makes it easy to look up the specific heat capacity of a material for calculations and comparisons.

Measuring Temperature

Temperature is commonly measured using thermometers that rely on the expansion of substances in response to heat. The most widely used thermometers contain liquid mercury or alcohol that expands when heated and contracts when cooled. This expansion and contraction drives the temperature readings on the thermometer’s scale.

There are several temperature measurement scales used today, with the most common being Fahrenheit (°F), Celsius (°C), and Kelvin (K). On the Fahrenheit scale, water freezes at 32°F and boils at 212°F. The Celsius scale, also known as centigrade, sets the freezing point of water at 0°C and the boiling point at 100°C. The Kelvin scale is an absolute temperature scale based around the idea of absolute zero, the coldest theoretical temperature. It uses the same size degree as Celsius, but sets the zero point at absolute zero rather than the freezing point of water. Temperatures on the Kelvin scale are expressed using the unit Kelvin rather than degrees.

Most countries today use the Celsius scale for common temperature measurement needs. Fahrenheit is still widely used in the United States. The Kelvin scale has applications in scientific contexts when precision is important.

Digital thermometers and thermocouples utilize electronic sensors to precisely measure temperature. Infrared thermometers can measure surface temperature remotely using a beam of infrared light. Each approach to temperature measurement has advantages for certain uses, but all provide quantitative measurement of this important physical property.

Applications

Being able to differentiate between specific heat and temperature is important in many real-world applications.

For example, when cooking, the specific heat of water determines how much heat is needed to raise the temperature to boiling. Water has a high specific heat, so it takes a lot of energy to heat up. This is why boiling water takes time. In contrast, the cooking oil in a frying pan has a lower specific heat, so it heats up much quicker.

In chemistry and physics labs, scientists use calorimeters to measure the specific heat of unknown substances. By tracking temperature changes as heat is added, they can calculate the specific heat using the formula q=mcΔT. This helps identify materials based on their thermal properties.

Weather scientists look at specific heat of air and water when forecasting temperatures. Air has low specific heat so its temperature changes quickly. Large bodies of water have high specific heat so oceans and lakes warm up and cool down slower. This moderates coastal temperatures.

Engineers use specific heat when designing systems like heating coils and heat sinks for computers. Knowing the specific heat determines how much a material will heat up based on energy input or dissipate heat to the surroundings.

Understanding the difference between the intensive property of specific heat and the state property of temperature is key for properly applying thermal physics concepts.

Summary

In summary, the key differences between specific heat and temperature are:

Specific heat is the amount of heat required to raise the temperature of 1 gram of a substance by 1°C. It is an intensive property that is dependent on the type of material and molecular structure.
Temperature measures how hot or cold an object is. It refers to the average kinetic energy of molecules and is measured on a temperature scale (Kelvin, Celsius, Fahrenheit).
Specific heat has units of J/g°C while temperature simply has units of degrees on a particular temperature scale.

Specific heat depends on the material and bonding while temperature does not depend on the material.
Specific heat is used in calculations relating heat transfer and energy while temperature is a quantity that is measured.

So in summary, specific heat is an intrinsic, quantitative property of a substance while temperature is a measured state that depends on kinetic energy.