Thermal Properties of Heat – Conductors of Heat

Thermal Properties of heat

 Key Concepts

1. Good conductors of heat
2. Poor conductors of heat
3. Temperature
4. How do we measure temperature?
5. What happens to a body when temperature increases?

Explanation

Introduction to the heat: 

Heat is the form of energy that always transfers from the hot body to the cold body. 

The study of heat and heat transfer is called thermodynamics, in which ‘thermo’ means heat and ‘dynamics’ means measurement. 

The unit of heat is joules in the SI system and ergs in the CGS system. 

Points to be remembered: 

1. Heat is a form of energy. 

2. It is measured in calories. 

3. Change in the heat is measured using a calorimeter. 

4. Joules is the unit of heat in the SI system. 

Conductors of heat: 

The substance which allows heat to pass through it is called conductor of heat. 

Conductors of heat are divided into two types: 

1. Good conductors of heat. 

2. Poor conductors of heat.  

Good conductors of heat: 

The substances which allow heat to pass through them are called good conductors of heat. 

Examples: 

1. Iron 

2. Steel 

3. Copper 

4. Aluminum 

Note: All metals conduct heat which means good conductors don’t burn when exposed to heat, but good conductors get heated up. 

Poor conductors of heat: 

The substances which don’t allow heat to pass through them are called poor conductors of heat. 

Examples: 

1. Paper 

2. Plastic 

3. Coal 

4. Wood 

Note: Poor conductors are substances that catch up a fire upon heating. 

Temperature:  

The degree of hotness and coldness of a body is called temperature. 

Important points to remember: 

1. The temperature in a body is directly proportional to the average kinetic energy in a body. 

2. Temperature is measured on three different scales. (Celsius, Fahrenheit and Kelvin) 

3. Temperature is measured using a thermometer. 

Types of thermometers: 

1. Clinical thermometer 

2. Laboratory thermometer 

3. Six’s maximum and minimum thermometer 

Clinical thermometer: 

A clinical thermometer is used to measure the body temperature. It uses mercury as the indicator, and the scale in the thermometer are both Celsius and Fahrenheit. 

Laboratory thermometer: 

A Laboratory thermometer is used in the chemical labs, which measures the temperature of  

different chemicals and substances. It uses alcohol as the indicator and has only a Celsius scale. 

Six’s maximum and minimum thermometer : 

Six’s maximum and the minimum thermometer is used to measure the environmental  

temperature, the maximum and minimum temperature, and it uses alcohol and mercury as the  

indicators. It has only a Celsius scale. 

What if the temperature of the body increases? 

For the three states of matter  

1. Solids 

2. Liquids  

3. Gases  

If the temperature is increased in any substance, the kinetic energy in the body is increased. 

Solids: 

If the temperature increases, solids expand, and some solids may catch fire. The expansion of the solids depends upon the material used and the melting point of the solids. 

E.g., metals when heated, expand, and non-metals catch fire. 

Liquids: 

If the temperature is increased, liquids expand, and some liquids may evaporate. The evaporation of the liquids depends upon the boiling points of the liquids. 

E.g., water boils at 100 ⁰C, and alcohol is evaporated at the same temperature. 

Gases: 

If the temperature increases, all gases expand, and there are no material and temperature constraints in the gases. 

Summary

Conductors of heat:

The substance which allows heat the pass through them is called the conductor of heat.

Good conductors of heat:

The substances which allow heat to pass through them are called good conductors of heat.

Poor conductors of heat:
The substances which don’t allow heat to pass through them are called poor conductors of heat.

Temperature:

The degree of hotness and coldness of a body is called temperature.

What if the temperature of the body increases?

If the temperature is increased in any substance, the kinetic energy in the body is increased.