# Gas Pressure & units of measurement

## What is pressure

Gases cause a physical focre on an object or a containers which causes pressure. Pressure will increase as the speed of molecules increases rate because the greater the force of collision. There are different units of measurement of pressure such as Torr, ATM, Pa.

## What are the messurments and how it is measured

Torr is equal to a millimeter of mercury

ATM or atmosphere, pressure of air at sea level

Pascal is equal to one newton per square meter. A newton is the force necessary to accelerate one kilogram by one meter per second squared.

1 ATM = 760 mmHg = 101.325 kPa = 101,325

## What is a barometer?

A barometer is a tool for measuring atmospheric pressure. The barometer is an instrument that in used for weather by measuring the weight of the air in the atmosphere. There are two types of barometer the aneroid barometer invented by Lucien Vidie and the first one invented by Evangelista Torricelli called the mercurial barometer.

## The invention of the first barometer

Torricelli used mercury in a vacuum experiment. By filling a four-foot long glass tube with mercury and inverted the tube into a dish. He noticed that not all of the mercury had escaped from the tude and made observations. He began to notice the variation in height of the mercury from day to day and that it was caused by the changes in the atmospheric pressure.