Thermal Expansion - Why are gaps left between railway tracks? | #aumsum #kids #science

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10 Mar 201704:19

Summary

TLDRThe script explains thermal expansion, a phenomenon where matter expands when heated. It illustrates this with examples like a thermometer's mercury rising in hot water and gasoline overflowing when heated. The script then relates this to railway tracks, explaining why gaps are left between rails to accommodate expansion and prevent accidents due to bending.

Takeaways

🔥 Thermal expansion is the phenomenon where matter expands when heated.
🌡️ A thermometer works by showing the rise in mercury level due to thermal expansion when placed in hot water.
💧 Mercury, being a liquid at room temperature, expands and causes the level to rise in a thermometer.
🚗 Gasoline expands when heated, which can cause it to overflow if not given space to expand, as seen in a filled gasoline tank.
🌞 Exposure to sunlight can heat gasoline in a tank, leading to expansion and potential overflow.
🛤️ Rails made of steel expand when heated, which can cause them to bend if not allowed to expand.
🔩 Railway tracks are made of steel rails that need space to expand to prevent bending and potential accidents.
🚉 Small gaps between rails are intentionally left to provide room for expansion and contraction of the steel rails.
🌡️ Thermal expansion not only occurs in summer but also due to friction between train wheels and rails.
🛑 Gaps between rails are crucial for preventing rail bending and ensuring the safety of train operations.

Q & A

What is thermal expansion?
-Thermal expansion is the tendency of matter to expand when heated and contract when cooled. It occurs in solids, liquids, and gases.
Why does the level of mercury in a thermometer rise when it is placed in hot water?
-The level of mercury in a thermometer rises when placed in hot water due to thermal expansion. The mercury expands as it heats up, causing the level to rise.
How does thermal expansion affect gasoline in a tank?
-Gasoline expands when heated, which can cause it to overflow if the tank is filled to the brim with no space for expansion. This is why gasoline may come out of a hot, full tank.
Why do railway tracks have gaps between the rails?
-Railway tracks have gaps between the rails to allow for thermal expansion. This prevents the rails from bending and causing accidents due to the expansion of steel when heated.
What happens to steel when it is heated?
-When steel is heated, it expands due to thermal expansion. This property is utilized in various applications, including the design of railway tracks.
How do the gaps between rails prevent accidents on railway tracks?
-The gaps between rails provide space for the rails to expand without bending. This prevents the train from derailing, thus avoiding accidents.
Can thermal expansion cause physical damage to objects?
-Yes, if objects do not have space to accommodate thermal expansion, they can be damaged or deformed, such as rails bending if not designed with gaps.
Why is it important to understand thermal expansion in the context of thermometers?
-Understanding thermal expansion is crucial for thermometers because it allows for accurate measurement of temperature changes by observing the expansion of the liquid inside.
What is the role of the small bulb in a thermometer?
-The small bulb in a thermometer contains the liquid (like mercury) that expands when heated, which is then measured by the rise in the liquid level within the narrow tube.
How does the continuous friction between train wheels and rails contribute to thermal expansion?
-The friction between train wheels and rails generates heat, which can cause the rails to expand. The gaps between the rails provide space for this expansion due to friction.
Are there any other materials besides steel that also expand when heated?
-Yes, many materials expand when heated, including metals like aluminum and copper, as well as some plastics and liquids.

Outlines

00:00

🔥 Thermal Expansion Explained

This paragraph introduces the concept of thermal expansion, explaining how matter tends to expand when heated. It uses the example of a thermometer filled with mercury to illustrate how liquids expand upon heating, causing the mercury level to rise. It also discusses the expansion of gasoline in a tank when heated, which can lead to overflow. The paragraph concludes with a discussion on how rails expand due to heat, and the importance of leaving gaps between them to prevent accidents caused by bending.

Mindmap

Keywords

💡Thermal Expansion

Thermal expansion is the phenomenon where materials increase in volume in response to an increase in temperature. It is a fundamental concept in physics that applies to all states of matter: solids, liquids, and gases. In the context of the video, thermal expansion is used to explain why the level of mercury in a thermometer rises when it is heated. The script also uses this concept to illustrate the importance of gaps between railway tracks to prevent them from bending and causing accidents due to the expansion of steel rails in hot weather.

💡Mercury

Mercury is a chemical element and a heavy, silvery, liquid metal at room temperature. It is commonly used in thermometers due to its high coefficient of expansion, meaning it expands noticeably with small changes in temperature. In the video script, the rise in the level of mercury in a thermometer is used as a visual demonstration of thermal expansion when the thermometer is placed in hot water.

💡Thermometer

A thermometer is an instrument used to measure temperature. It typically consists of a narrow glass tube containing a liquid, such as mercury, which expands and contracts with temperature changes. The script mentions how the level of mercury in a thermometer rises due to thermal expansion when it is exposed to heat, providing a clear example of how thermal expansion works.

💡Gasoline

Gasoline, also known as petrol, is a transparent, petroleum-derived liquid that is used primarily as a fuel in internal combustion engines. The script discusses how gasoline expands when heated, which can cause it to overflow from a container if there is no space for expansion. This is an example of thermal expansion in liquids and serves as a cautionary tale about the need for space in containers to accommodate volume changes due to temperature.

💡Steel

Steel is an alloy consisting mainly of iron and a small amount of carbon, and it is known for its strength and durability. The video script explains that steel expands when heated, which is a critical factor in the design of railway tracks. To prevent the tracks from bending and causing derailments, gaps are left between the rails to allow for this expansion due to thermal changes.

💡Rails

Rails are the metal components that form the tracks on which trains run. They are typically made of steel and are laid end-to-end to form a continuous path. The script highlights the importance of leaving gaps between rails to accommodate thermal expansion. Without these gaps, the rails could bend and cause trains to go off track, leading to potential accidents.

💡Friction

Friction is the force that resists the relative motion or tendency of such motion of two surfaces in contact. In the context of the video, friction is mentioned as a factor that generates heat between train wheels and rails, which can lead to thermal expansion. This example illustrates how everyday interactions can have a significant impact on the physical properties of materials.

💡Bending

Bending refers to the deformation of a material in response to an applied force. In the video script, bending is used to describe what happens to railway tracks if they are not designed to accommodate thermal expansion. The bending of the tracks can lead to serious safety issues, such as train derailments, underscoring the importance of understanding and planning for material behavior in engineering.

💡Gaps

Gaps are spaces left between objects to allow for movement or expansion. The script explains that gaps are intentionally left between railway tracks to prevent them from bending due to thermal expansion. This is a practical application of the understanding of material properties in engineering to ensure safety and prevent accidents.

💡Safety

Safety refers to the condition of being protected from or unlikely to cause harm, damage, or other non-desirable outcomes. The video script emphasizes the importance of safety in the design of railway tracks, where leaving gaps between rails is a measure to prevent accidents caused by thermal expansion. This keyword highlights the broader implications of understanding thermal expansion for public safety.

💡Contraction

Contraction is the process of becoming smaller or shorter, typically as a result of cooling. While the script primarily focuses on thermal expansion, it also mentions the opposite process, contraction, which occurs when materials cool down. Understanding both expansion and contraction is crucial for designing systems that can withstand temperature changes without failure.

Highlights

Thermal expansion is the tendency of matter to expand on heating.

Thermal expansion occurs in solids, liquids, and gases.

A thermometer demonstrates thermal expansion with mercury rising when heated.

The mercury in a thermometer expands due to heat, causing the level to rise.

Gasoline expands when heated, which can cause it to overflow if not given space.

Expansion of gasoline can force it out of a full tank when exposed to heat.

Rails are made of steel, which expands when heated and contracts when cooled.

If rails are not allowed to expand, they can bend and cause trains to derail.

Small gaps between rails prevent them from bending due to thermal expansion.

Gaps in rails provide space for expansion during summer and due to friction.

These gaps prevent rail accidents by allowing for expansion.

The concept of thermal expansion is crucial for understanding material behavior under heat.

Understanding thermal expansion is important for designing safe structures like railway tracks.

Thermal expansion can have practical implications in everyday life, such as with thermometers and gasoline tanks.

The application of thermal expansion principles helps prevent accidents and ensure safety.

Railway engineers use the knowledge of thermal expansion to design tracks that can withstand temperature changes.

The phenomenon of thermal expansion is a fundamental concept in physics with real-world applications.