So the school holidays are just around the corner and we’ve thought of a great way to keep the kids entertained for a day! Here’s a science experiment that will help the kids learn about how thermal insulation works.
What do you do in the middle of winter when it starts to get cold? Most people would turn on a heater, put on an extra layer of clothes and snuggle up under a comfy blanket. If you’re going outside you’ll put on a jacket but have you ever considered why and how a jacket helps you keep warm?
In this activity, we’re going to demonstrate how thermal insulation works and help you find the best way to keep warm this winter!
Heat is just a form of energy. To heat something up, for example a hot chocolate, you’ll use energy from your microwave or electric jug. This energy comes in the form of electricity or gas. Once you’re drink is nice and hot it immediately starts loosing heat. The longer you wait, the cooler it gets.
This is due to a phenomenon called heat transfer. This is where the flow of energy, in this case, heat, starts to flow from one object to another. The rule is that heat energy is always transferred from the hotter object to the colder one. In this example, the heat from the hot chocolate is being transferred out of the cup and into its surrounding air which is usually going to be colder than the drink.
Once both objects reach the same temperature the heat transfer will stop. This type of heat transfer in liquids or gases is called convection.
Another type of heat transfer is known as conduction. In this energy moves through a substance from one particle to another. A good example of conduction is when you put a pot on the stove, the pot and handle start to heat up.
Finally, heat can also be transferred through radiation. If you’ve sat around a bonfire before, you’ll know that the fire gives off a lot of heat. Although you’re not touching the fire, you feel the heat as it radiates out from the fire, even if it’s a really cold evening.
So let’s return to your cup of hot chocolate. If you want to keep your drink nice and hot you might be interested to know how to reduce or slow heat transfer so the drink stays hot and the answer is thermal insulation.
Insulation creates a thermal barrier between a hot and cold object that reduces or slows heat transfer by either reflecting thermal radiation or decreasing thermal conduction and convection. The type of insulation material used in the barrier will determine its effectiveness at slowing or reducing heat transfer. Barriers that conduct heat poorly are good thermal insulators whereas materials that conduct heat well will have low insulating capabilities. This is how thermal insulation works.
In this experiment you will test which materials make good and bad thermal insulators. Here are the materials you’ll need for the experiment
Are you ready to learn how thermal insulation works? Let’s get started!
Did your hot water cool down significantly during the 10 minutes inside the fridge? Although the fridge temperature is very low, your hot water has a high temperature. As heat energy flows from the hot object to the cold object, the heat energy from your hot water will be transferred to the surrounding cold air inside the fridge once you put the glass jars inside.
The most significant mechanism of heat transfer in this case is convection, which means that the air just next to the hot jar is warmed up by the hot water. Then, the warm air is replaced with cold air, which is also warmed up. At the same time, the cold air cools down the water inside the jar. The heat of the hot water is transported away by the flow of cold air around the cup. If you left the jars in the fridge long enough, you might have observed that the temperature changes until the hot water reaches the temperature inside the fridge. Without a temperature difference between the water and the fridge, the heat transfer will stop.
Heat from the water is also lost through conduction: the transfer of heat through the material, which is dependent on the thermal conductivity of the material itself. The glass jar can conduct heat relatively well. You notice that when you touch the glass jar with the hot water the glass feels hot as well.
What effect did the different wrapping materials have? You should have noticed that with wrapping materials, the temperature of the water after 10 minutes inside the fridge was higher compared to the unwrapped control. Why? Wrapping the glass jar reduces the heat transfer from the hot water to the cold air inside the fridge. Using wrapping materials that have a very low thermal conductivity reduces the heat loss through conduction. At the same time the insulator can also disrupt or reduce the flow of cold air around the glass jar, which results in less heat loss via convection.
One way of reducing convection is creating air pockets around the jar, for example, by using insulators such as bubble wrap, fabric or wool, which have a lot of air pockets. Air in general is a good thermal insulator, but it can transmit heat through convection. However, if the air pockets inside the insulating material are separated from each other, heat flow from one air pocket to another cannot happen easily.
This is the reason why you should have measured the highest temperature in the bubble-wrapped jar and fabric-wrapped jar. This also explains why most of our clothes are made of fabrics and why you stay warmer when you put on an extra jacket. Paper and foil make it easier for the heat to escape because they don’t have many air pockets.
Now that you have some understanding about how thermal insulation works it should give you a better understanding of why home’s need to be insulated. Roof, floor and wall insulation are all very important to keeping you and your family warm during winter!
We hope you enjoyed learning how thermal insulation works!