9.5 Measuring Temperature
2 min read•june 18, 2024
is all about . As things heat up, molecules move faster and spread out. When they cool down, molecules slow down and get closer together. This affects how substances behave and is key to understanding many everyday phenomena.
Measuring involves different scales like and . Converting between them is useful for cooking, weather forecasts, and science. Understanding temperature helps us make sense of the world around us, from why bridges expand to how our bodies regulate heat.
Temperature and Molecular Motion
Temperature and molecular motion
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- Measures the average of molecules in a substance
- Energy of motion possessed by molecules
- Increases cause molecules to move faster and collide more frequently
- Leads to expansion as molecules spread out due to increased motion (gases, liquids)
- Decreases cause molecules to move slower and collide less frequently
- Leads to contraction as molecules move closer together due to decreased motion (solids)
- Measured using a
Fahrenheit vs Celsius conversions
- Two common temperature scales used to measure temperature
- Fahrenheit to Celsius conversion:
- Subtract 32 from the Fahrenheit temperature
- Multiply the result by
- Celsius to Fahrenheit conversion:
- Multiply the Celsius temperature by
- Add 32 to the result
- Mental math approximations for quick estimates
- Celsius from Fahrenheit: subtract 30 from °F and divide by 2 (86°F ≈ 28°C)
- Fahrenheit from Celsius: double °C and add 30 (25°C ≈ 80°F)
Temperature Scales and Concepts
- : An absolute temperature scale with 0 K representing
- Absolute zero: The lowest possible temperature where molecular motion theoretically stops
- : The tendency of matter to change in volume in response to temperature changes
- : The movement of thermal energy from one object or system to another
Temperature in real-world applications
- Cooking and baking require temperature conversions
- Recipe calls for 180°C, convert to Fahrenheit:
- Weather forecasts and climate data use different scales
- London temperature 20°C, convert to Fahrenheit:
- Temperature changes affect properties and behavior of substances
- Water freezes at 0°C (32°F) and boils at 100°C (212°F) at standard atmospheric pressure
- Bridges and railways expand and contract due to temperature changes
- and gaps prevent damage (Golden Gate Bridge, San Francisco)
Key Terms to Review (20)
Absolute zero: Absolute zero is the theoretical temperature at which a system's entropy reaches its minimum value, and molecular motion comes to a near halt, measured at 0 Kelvin or -273.15 degrees Celsius. It serves as the lower limit of the thermodynamic temperature scale, playing a crucial role in understanding the behavior of matter at extremely low temperatures.
Boiling point: The boiling point is the temperature at which a liquid's vapor pressure equals the atmospheric pressure surrounding it, causing the liquid to change into vapor. This point is crucial in understanding phase changes and is influenced by factors such as altitude and atmospheric pressure, as well as the properties of the substance being heated.
C = (F - 32) × (5/9): This equation converts temperature from Fahrenheit (F) to Celsius (C) by taking the Fahrenheit temperature, subtracting 32, and then multiplying the result by 5/9. Understanding this formula is essential for accurately comparing temperatures in different scales, as Celsius and Fahrenheit are the two most commonly used temperature systems worldwide.
Celsius: Celsius is a temperature scale where 0 degrees represents the freezing point of water and 100 degrees represents the boiling point of water at standard atmospheric pressure. This scale is widely used in most countries around the world for everyday temperature measurements, making it essential for understanding weather, cooking, and scientific research.
Celsius scale: The Celsius scale is a temperature measurement system where water freezes at 0 degrees Celsius and boils at 100 degrees Celsius under standard atmospheric conditions. This scale is widely used around the world for everyday temperature measurement, making it crucial for scientific and practical applications alike.
Degree Celsius: The degree Celsius is a unit of measurement for temperature, defined by the freezing point of water at 0 degrees and the boiling point at 100 degrees under standard atmospheric conditions. This scale is widely used around the world for everyday temperature measurements in weather forecasts, scientific experiments, and cooking. The degree Celsius is a part of the metric system and is often seen as more intuitive for common temperatures experienced in daily life compared to other temperature scales.
Degree Fahrenheit: The degree Fahrenheit is a unit of measurement for temperature, defined by the freezing point of water at 32 degrees and the boiling point at 212 degrees, under standard atmospheric pressure. This scale is primarily used in the United States and a few other countries, providing a way to measure thermal energy in everyday contexts such as weather reporting and cooking.
Expansion Joints: Expansion joints are flexible connections within structures that allow for movement caused by temperature changes, thermal expansion, or contraction. These joints are essential for maintaining the integrity of buildings and infrastructure as they accommodate the expansion and contraction of materials in response to temperature fluctuations.
F = (9/5)C + 32: The equation F = (9/5)C + 32 is the formula used to convert temperature from Celsius (C) to Fahrenheit (F). It illustrates the relationship between these two temperature scales, highlighting how a change in degrees Celsius corresponds to a specific change in degrees Fahrenheit. Understanding this formula is crucial for interpreting temperature data in various contexts, as it enables conversions that are essential in fields like science, meteorology, and everyday life.
Fahrenheit: Fahrenheit is a temperature scale that defines the freezing point of water at 32 degrees and the boiling point at 212 degrees, with 180 degrees separating the two points. This scale was developed by Daniel Gabriel Fahrenheit in the early 18th century and is primarily used in the United States and some Caribbean nations. Understanding this scale is essential for accurately measuring and comparing temperature in various contexts.
Fahrenheit scale: The Fahrenheit scale is a temperature measurement system where the freezing point of water is defined as 32 degrees and the boiling point as 212 degrees at standard atmospheric pressure. Developed by Daniel Gabriel Fahrenheit in the early 18th century, this scale is commonly used in the United States and some Caribbean nations for everyday temperature readings, including weather forecasts and cooking.
Freezing point: The freezing point is the temperature at which a substance changes from a liquid state to a solid state. This transition occurs when the kinetic energy of the molecules in the liquid decreases to the point that they can no longer overcome the attractive forces between them, leading to the formation of a solid structure. The freezing point varies for different substances and can be affected by factors such as pressure and impurities.
Heat Transfer: Heat transfer refers to the process by which thermal energy moves from one object or system to another due to a temperature difference. This movement can occur through conduction, convection, or radiation, and it plays a crucial role in various scientific and engineering applications, particularly in understanding how temperature is measured and maintained in different environments.
Kelvin: Kelvin is the SI unit of temperature, symbolized as K, and it is used to measure thermodynamic temperature. Unlike Celsius and Fahrenheit, the Kelvin scale starts at absolute zero, the point at which all molecular motion ceases, making it a critical scale in scientific research and applications, especially in physics and engineering.
Kinetic Energy: Kinetic energy is the energy that an object possesses due to its motion. The amount of kinetic energy an object has depends on its mass and velocity, expressed mathematically by the formula $$KE = \frac{1}{2}mv^2$$, where 'm' is mass and 'v' is velocity. This form of energy plays a significant role in understanding temperature, as the motion of particles at a molecular level directly influences thermal energy and temperature measurements.
Molecular motion: Molecular motion refers to the movement of molecules within a substance, which is a key factor in determining its temperature and state of matter. The speed and type of molecular motion vary depending on whether a substance is a solid, liquid, or gas, affecting how energy is transferred within that substance. Understanding molecular motion helps explain temperature measurements and the behavior of matter under different thermal conditions.
Temperature: Temperature is a measure of the average kinetic energy of the particles in a substance. It indicates how hot or cold an object is and is typically measured in degrees Celsius (°C), Fahrenheit (°F), or Kelvin (K).
Temperature: Temperature is a measure of the average kinetic energy of the particles in a substance, indicating how hot or cold that substance is. This physical quantity is essential in various fields, affecting processes such as weather patterns, cooking, and industrial operations. Different temperature scales like Celsius, Fahrenheit, and Kelvin are used to quantify temperature, making it easier to communicate and understand thermal conditions.
Thermal expansion: Thermal expansion refers to the increase in volume or size of a material when it is heated. As the temperature rises, the particles in a substance move more vigorously, causing them to occupy more space. This principle is crucial in various applications, from engineering to everyday experiences, as it affects how materials behave when subjected to temperature changes.
Thermometer: A thermometer is a device used to measure temperature, typically indicating how hot or cold an object or environment is. It operates on principles such as thermal expansion or changes in electrical resistance, allowing it to provide accurate readings across various scales. Understanding thermometers is crucial for applications in science, weather forecasting, and even cooking, as they help us gauge thermal conditions effectively.