Thermal Energy: Conduction (Veronica Serna)

Title: A Parlour Trick or Science? The Fireproof Balloon

Principle(s) Investigated: Heat transfer, conduction, some review of the states of matter/properties of matter

Standards:

SEP: Constructing explanations and designing Solutions

Systems and System Models

• Models can be used to represent systems and their interactions – such as inputs, processes, and outputs – and energy and matter flows within systems. (MS-PS3-2)

Materials: A candle, small container of play-doh, matches or lighter, 2 balloons, water, goggles

https://classroom.google.com/c/MzQ4MjkyMjI1Mjda

Class Code: 5yhbc85

https://www.online-stopwatch.com/

Procedure:

1. The instructor should set the stage, announcing to students that they are going to observe a Victorian parlour trick.

2. We will fill two balloons up, one with air and one with air and water.

3. The instructor should demonstrate lab safety by putting on goggles.

4. The instructor will stick the candle into the tub of play-doh so it is secure, you may also use a candle holder or something else steady to keep flame secure then light the flame.

5. The instructor ask students to make observations then will hold the balloon with air over the flame. The balloon should burst!

6. The instructor will ask students to make observations for the next balloon. The teacher may ask a student to hold the balloon over the flame (give student goggles too). This time the balloon should not burst!

7. Pose the question, why?

8. Students will now perform an online lab from which they will develop a model. They will click on the posted Google Classroom, login and follow directions to record their observations and model drawing. (think-pair-share or share docs)

9. Students will follow instructions to continue to an online lab and online modeling.

10. Come together and share or instructor can open a doc to share. Students will then fill out an exit ticket to show that they understood or did not understand select targeted concepts from the lesson.

Student prior knowledge: Students should understand the states of matter, they should understand the different forms of energy transfer (Mechanical, Electrical, Light, Heath/Thermal,Sound, Chemical, Gravitational,etc)

Explanation:

A balloon is composed of thin latex, this allows heat to be quickly absorbed. The thin rubber cannot withstand the pressure from the warmed molecules of air inside and will burst.

When you add water to the balloon this allows the heat energy from the candle to efficiently transfer to the water. Water takes a considerable amount of energy to heat up, more than air because it has a higher heat capacity. "Heat capacity is a property of a material that describes how much heat energy is required to change the temperature of a substance by one degree Celsius. About one unit of heat energy is needed to warm the air one degree Celsius. Four times more heat energy is needed to warm the water one degree Celsius." (http://omp.gso.uri.edu/ompweb/doee/science/physical/chtemp6.htm)

Questions & Answers: Give three thought-provoking questions and provide detailed answers.

1. How did the water prevent the second balloon from popping?

When you add water to the balloon this allows the heat energy from the candle to efficiently transfer to the water.However, water takes a considerable amount of energy to heat up, more than air because it has a higher heat capacity.

2. Why did the first balloon pop almost instantaneously?

The molecules of air inside the balloon are gas molecules and when heated the pressure rises inside the balloon. The molecules are colliding and hitting the walls of thier container more frequently. The thin layer of latex can no longer contain the gas, and thus it pops, escaping.

3. How does this phenomena relate to the transfer of thermal energy?

In the first balloon we observe that the heat from the candle is transferred to the air inside the balloon. We know this because the cause of the balloon popping is the pressure from the air, bursting through because it cannot be contained in it's container (the balloon).

We observe in the second balloon that the heat from the candle is being transferred to the candle rather than the air. When an object is heated through direct contact/touch this is called conduction.

Applications to Everyday Life:

1. Sweat: Our body uses sweat as a means of cooling down. This is our bodies attempt at homeostasis, as the sweat evaporates taking that energy and cooling us off.

2. Weather: bodies of water such as the ocean/lakes, etc heat up slower than land because they need more energy from the sun to heat up. Water also cools faster than land, while land will retain heat longer than water. This is applicable to weather. Land near large bodies of water tend to have a climate with little variance in temperature, versus a piece of land that is further inland, away from the properties of water.

3. Calorimeter (measures heat capacity and changes in temperature during chemical reactions): Since water has the capacity to retain heat, is relatively inexpensive and is easy to measure it can be used in the process ofmeasuring the heat capacity and/or temperature during chemical reactions of other substances. "The specific heat of water (4.18 J/g x k) is well established and so as a system releases or absorbs energy from a surrounding water bath it can be measured". (Anderson,Paul)

More on this below:

https://youtu.be/SAR-5wdQKSY

Photographs:

The gas molecules inside the balloon would look similar to this diagram, note how they are colliding into the container, exerting more and more pressure as the temperature rises inside the balloon due to the heat transfer from the candle.

Note that the balloon bursts!

When the balloon is filled with water it does not pop, now note the properties of water below.

Videos: https://www.youtube.com/watch?v=qeDZQ9-gsjY

Source: Steve Spangler Science (note: he used the word suck incorrectly)