Pressure, volume and density

equation for pressure

pressure = force/area

what are the three gas laws

1. pressure and volume are inversely proportional

2. temperature and volume are directly proportional

3. temperature and pressure are directly proportional

why does decreasing volume in a fixed container increase pressure

decreasing the volume whilst keeping the number of particles the same will increase the concentration

in this smaller volume collisions between particles of gas and the walls of the container will be more frequent

this means that there's a greater number of collisions per unit area

what are the two factors that increase pressure of a gas

1. more collisions with the wall of the container

2. faster moving particles

why are temperature and volume directly proportional

gases expand when heated, as the hot air is less dense and so rises occupying a greater volume as they spread out

why are temperature and pressure directly proportional

thermal energy--> more kinetic energy---> particles move around faster----> so more frequent collisions

what is density

how much mass a substance has per unit of its volume

equation for density

Density = mass/volume

how do you reduce uncertainty in experimental measurements of density

1. take multiple measurements and calculate the mean

2. when measuring the density of a liquid, use a larger volume of liquid

how to calculate density of a regular object experimentally

1. measure the mass of the object using a top pan balance

2. calculate volume by doing lenghtx width x height

3. now use p=m/v equation

how to calculate density of an irregular object

1. measure mass of object using a top pan balance

2. to measure volume fill a eureka can up the spout with water, place the object in slowly lowering it using string, and the volume of water displaced from the eureka can into the measuring cylinder on the other side is the volume of the object

3. use p= m/v equation

explain why expanding a gas rapidly causes a decrease in temperature

when a gas expands the particles do work on the surroundings as they move apart. This work requires energy which is taken from the \KE of the gas particles leading to a decrease in temperature