Standard temperature and pressure

Do you know how sometimes it's hot outside and sometimes it's cold? Well, when people talk about "standard temperature", they're talking about a temperature that is the same no matter where you are or what time of year it is. It's kind of like when you have a favorite temperature in your house and you always set the thermostat to that same number.

As for "standard pressure", that's talking about how much air is pushing on things around us. It's like if you were trying to blow up a balloon but there was something heavy on top of it - it would be hard to blow it up because there's less space for air to go in.

Scientists and engineers use standard temperature and pressure as a way to compare things and make sure everyone is talking about the same thing. The standard temperature is usually around 25 degrees Celsius (77 degrees Fahrenheit), and the standard pressure is usually about 1 atmosphere - which is like having a heavy book sitting on top of something.

So, when people talk about things happening at "standard temperature and pressure", they're talking about a specific combination of temperature and air pressure that is the same no matter where you are.