Pemuaian Pada Zat

Summary

This video explains the concept of thermal expansion, where materials expand when heated, affecting solids, liquids, and gases. Real-life examples, such as expanding railway tracks, thermometers using liquid expansion, and hot air balloons, are explored. The video also covers the principle behind thermostats and electric irons, which use materials with different expansion rates to control temperature. The scientific explanation includes a formula for calculating linear expansion, highlighting the importance of thermal expansion in daily life applications like transportation, household appliances, and more.

Takeaways

• 😀 Thermal expansion refers to the increase in size or volume of materials when heated, affecting solids, liquids, and gases.
• 😀 Solids expand when heated, with a real-life example being the expansion of railway tracks during hot weather.
• 😀 If railway tracks are not spaced correctly, they could bend or cause accidents, like derailing trains, due to thermal expansion.
• 😀 Liquids also expand when heated. Thermometers use this property, with liquid mercury or alcohol rising to indicate temperature.
• 😀 Gases expand much more easily than solids and liquids. This property is used in balloon flight, where hot air causes the balloon to rise.
• 😀 Bimetallic strips are made of two metals with different expansion rates. These strips bend when heated, which is used in thermostats.
• 😀 Thermostats, like those in electric irons, use bimetals to automatically switch the appliance on or off based on temperature changes.
• 😀 The formula for calculating linear thermal expansion is Δl = l₀ * α * ΔT, where Δl is the change in length, l₀ is the original length, α is the coefficient of expansion, and ΔT is the change in temperature.
• 😀 In the example of a 100 cm iron bar heated from 30°C to 230°C, the change in length can be calculated using the formula and the coefficient of linear expansion for iron.
• 😀 Understanding the principle of thermal expansion is crucial in designing safe and functional systems, such as railway tracks, thermometers, and electrical appliances.

Q & A

What is thermal expansion?

Thermal expansion refers to the increase in size (length, area, or volume) of a material when it is heated. This expansion occurs due to the absorption of heat, which causes the particles of the material to move more vigorously, resulting in an increase in the distance between them.

How does thermal expansion occur in solids?

In solids, thermal expansion happens when heat is applied to the material, causing its particles to vibrate more. This leads to an increase in the dimensions of the solid, such as length, area, or volume. Conversely, the material will contract (shrink) if the temperature is lowered.

Why are gaps left between railway tracks?

Gaps are left between railway tracks to account for the thermal expansion of the tracks in hot weather. If the temperature increases, the tracks would expand, and without space between them, they could bend or even cause derailments. The gaps prevent this dangerous situation.

How does thermal expansion work in liquids, specifically in thermometers?

In liquids like mercury, thermal expansion occurs when the liquid absorbs heat, causing its volume to increase. In a thermometer, the expansion of mercury raises the level of the liquid inside the thermometer, providing a measurable change that corresponds to temperature.

How does thermal expansion apply to gases?

Gases are highly susceptible to thermal expansion. When gas particles are heated, they move faster and spread out, leading to an increase in volume. This principle is used in practical applications like hot air balloons, where the gas inside the balloon expands and becomes lighter, causing the balloon to rise.

What is the principle behind bimetallic strips?

Bimetallic strips are made of two metals with different coefficients of thermal expansion. When heated, one metal expands more than the other, causing the strip to bend. This bending is used in devices like thermostats to control temperature by turning circuits on or off based on the strip's movement.

What is the role of bimetallic strips in thermostats?

In thermostats, bimetallic strips are used to regulate temperature by bending when they expand due to heat. The bending action opens or closes an electrical circuit, controlling the heating or cooling mechanism, such as in electric irons or heaters.

How does the coefficient of linear expansion work?

The coefficient of linear expansion (alpha) measures how much a material expands per unit length when its temperature increases by one degree Celsius. For example, if the coefficient is 0.0011 per degree Celsius, a 1-meter length of the material will expand by 1.1 millimeters for every 100°C increase in temperature.

What is the formula for calculating the change in length due to thermal expansion?

The formula for calculating the change in length due to thermal expansion is: Δl = l₀ * α * ΔT, where Δl is the change in length, l₀ is the original length, α is the coefficient of linear expansion, and ΔT is the change in temperature.

How can you calculate the expansion of iron when heated from 30°C to 230°C?

To calculate the expansion of iron, use the formula Δl = l₀ * α * ΔT. For example, if the original length of iron is 1 meter, with a coefficient of linear expansion of 0.0011 per degree Celsius, and the temperature increases from 30°C to 230°C (ΔT = 200°C), the change in length will be 1 meter * 0.0011 * 200, which equals 0.22 meters or 22 millimeters.