Chemistry set 2 Flashcards
What do ‘gas laws’ do?
Gas laws describe how gas will behave.
Why are scientific laws not like legal laws?
Scientific laws describe how things behave, they do not give explanations.
What is needed to provide an explanation for a scientific law?
A theory provides and explanation for a scientific law.
Name the theory to explain how gasses behave.
Kinetic Molecular Theory of Gasses explains how gas behaves.
What is the first assumption of the gas theory?
- Particles (atoms or molecules) are constantly moving in straight lines until they collide with other particles or walls of their container
What is the second assumption of the gas theory?
- There is no loss of energy when a particle collides with another particle or the wall of the container.
What is the third assumption of the gas theory?
- the volume of the particles themselves is so small compare to the volume of the space they occupy that it is considered to be negligible (can be ignored)
What is the fourth assumption of the gas theory?
- the are no forces of attraction between particles because they are so far away from each other when they are in the gas state.
What is elastic collision?
Elastic collision is when particles collide and do not lose energy, this is only in the world of molecules.
What is inelastic collision?
In our world, when things collide they lose energy and slow down due to friction.
What does the Gas theory explain?
The gas theory explains pressure
What is pressure?
Pressure is the force of many molecules against the walls of a container.
What kind of pressure to molecules put on a container?
Molecules have an outward pressure on containers.
What happens if the pressure becomes stronger than the container?
An explosion happens when the pressure of the gas is greater than the strength of the container.
What kind of energy does gas have?
Gas has kinetic energy. (moving energy)
When the kinetic energy of a gas changes, what also changes?
The temperature rises if the gas’s kinetic energy increases.
In what three ways do we measure gas?
Volume, temperature and pressure are used to measure gas.
What is volume?
Volume is the amount of space the gas takes up.
How is gas volume measured?
Gas is measured in capacity units, milliliters (mL) and liters (L), or large volumes in kilolitres (kL)
Why are both Fahrenheit and Celsius based on water temperature?
Originally people were interested in knowing when water changes state, freezing and boiling points.
Do Fahrenheit and Celsius work well for gas?
No, because at zero gas particles are still moving.
Who was Anders Celsius?
Anders Celsius was a Swedish astronomer and physicist who invented celsius.
What is the absolute temperature scale?
The absolute temperature scale was created to show when gas particles stop moving.
What is another name for the absolute temperature scale?
Kelvin scale, after its creator Lord Kelvin of England.
What is the freezing point of water in Kelvin?
0 degrees Celsius is 273 Kelvin.
Do you use degrees with Kelvin scale?
No, you just say the number Kelvin. Ie 43 Kelvin
How do you convert a celsius to Kelvin?
Just add 273 to the celsius to get its kelvin equivalent.
What system is most commonly used for scientific applications?
The metric system
What is the equation (math sentence) for pressure?
P=F/A P is pressure, F is force, A is area
Force is measured in what unit?
Force is measured in units called newtons (N)
How is area represented in an equation?
area is shown as m2 or meters squared
What is a pascal? (Pa)
A pascal is a unit of pressure N/m2 and is named after Blaise Pascal
1000 Pa is called
a kilopascal kPa
100 kPa is called…
a bar
What is psi?
PSI is pounds per square inch, which is an imperial (not metric) measurement
Where do we still use psi every day?
We measure tire pressure in psi
How do we measure atmospheric pressure?
We use a barometer
What fills a barometer?
Mercury fills a barometer.
What measurement is used in a barometer
mm Hg which means millimeters of mercury
mm Hg can be converted to what unit?
mm Hg can also be read as 1 torr
How does a barometer measure air pressure?
The mercury is in a vacuum, so that the air molecules push down the container, and the mercury is forced into the tube.
what is a baseline measurement for air pressure?
The air pressure at sea level is the baseline.
What does a barometer read at sea level?
at sea level, a barometer reads 760 mm (14.696 psi) or 101.325 kPa
What is the air pressure at sea level also known as?
At sea level they say it is ‘standard atmosphere’ or atm
ATM was recently replaced by
they use the bar measurement now, or 100 kPa
What instrument do you use to measure gas pressure?
You use a pressure gauge to measure gas pressure.
How does a tire gauge work?
air pushes a fluid through a tube, which pushes a piston on a spring. The piston travels relative to the pressure in the tire.
What is a piece of equipment that tells you psi?
A calibrating rod gives you a psi measurement.
