![](https://images.ecency.com/DQmcwoyVxgh9voTxtmndgqgXrhCNsqnPDHmz9tHzkAzbrFn/1687550150138.png)
     
Thermal Expansivity is the change in length of a materials due to heat. It is sometimes an advantage or a disadvantage, matter states like solid and liquid can expand because of heat.

**The advantage of Thermal                  Expansivity**

* **Expansion in bimetallic strips**
A bimetallic strip consist of metals kept side by side. It is used in thermostat and fire alarm. When there's too much heat in the house or room, the bimetallic strip in the fire alarm bends to the contact point which makes the alarm ring

![](https://images.ecency.com/DQmW5Ma1yivu3QyoBdx3M64Bhu5pFWFYhrMeNXKf9ornURn/1687547663350.png)

 **The disadvantage of  termal expansivity**
* **Expansion on railway line.**
When much heat is applied on a railway line, it tends to expand and loosen itself from the line which can lead to train crash. 

![](https://images.ecency.com/DQmUDJgjoSYxon8K6DLy5oPUwaxkQAsiLauCX7QZZsiVFD7/1687550202515.png)


**Transfer of heat** 
Heat can be transfer through the following ways ;
1. Radiation
2. Conduction 
3. Convention 
** Radiation**: is a type of heat transfer where heat is transferred without contact with each other for instance, one feeling heat from the sun without touching it.

**Conduction**: In this type, heat is transferred through direct contact for instance, the hotplate and stew pot.

**Convention**: This is a type of heat transfer where the material receiving heat is inside another hot material, for example, egg in  hot water. 

**Materials that doesn't transfer heat**
Plastic
Glass
Rubber etc.
**Materials that transfer heat**
Aluminum
Iron
Steel etc.
 Proof of heat transfer
![](https://images.ecency.com/DQmf4NTfqnZK68XvZqfKrehD9xNSgLCzjgAomYPreKCNhqL/1687548860521.png)

In a thermocool flask there is :
A cork stopper as the lid to avoid heat loss through radiation. 
A cork support or shock absorber to prevent heat loss through conduction.
The outer body made of plastic to preven heat loss through radiation.
A silver wall to prevent heat loss through covention as it is inside the vacuum which is hot and a doulble wall glass to prevent heat loss through radiation. I will stop so far,  in my next I post I will calculate thermal expansivity. 

Thanks for stopping by ❤️❤️❤️