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The standard conditions for measuring gas volumes are a temperature of 0°C and a pressure of 1 atmosphere.
In more detail, these conditions are often referred to as Standard Temperature and Pressure (STP). The standard temperature is defined as 0°C, which is equivalent to 273.15 Kelvin. This is the freezing point of water and is used as a baseline for many scientific measurements. The standard pressure is defined as 1 atmosphere (atm), which is the average atmospheric pressure at sea level.
These conditions are used because they provide a consistent and reproducible environment for measuring and comparing the volumes of different gases. Under these conditions, one mole of any ideal gas occupies a volume of 22.4 litres. This is known as the molar volume of a gas at STP and is a useful concept in many areas of chemistry.
It's important to note that these are not the only conditions under which gas volumes can be measured. For example, in some fields, a temperature of 25°C and a pressure of 1 atmosphere are used, known as Normal Temperature and Pressure (NTP). However, for most purposes in GCSE Chemistry, you'll be working with STP.
Remember, gases can behave differently under different conditions of temperature and pressure. This is described by the gas laws, which you'll learn about in more detail. But for now, just remember that when we talk about the volume of a gas, we usually mean its volume at STP.
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