P1 Matter Flashcards
What is the billiard ball model?
-Discovered by dalton in 1803.
-Different elements have different atoms.
-Atoms of the same element are identical.
-Atoms can’t be divided.
-Atoms can join to make new substances.
-Atoms make up all substances.
What is the plum pudding model?
-Discovered by JJ Thompson in 1897.
-The atom is a weak, positively charged sphere embedded with negative electrons.
How was the plum pudding model discovered?
-JJ Thompson used a cathode-ray tube to conduct an experiment which showed that there are small particles inside atoms.
-This disproved Dalton’s theory about atoms not splitting.
What is the planetary model?
-Discovered by Rutherford in 1911.
-The atom has a small, central nucleus of concentrated positive charge.
-Electrons orbited around the nucleus.
-He also discovered protons.
How was the planetary model discovered?
-Rutherford and his 2 students, Geiger and Marsden, fired positive alpha particles at thin, gold foil.
-They were supposed to go straight through however some particles deflected or rebounded back.
What is Bohr’s model?
-Discovered in 1913.
-Electrons orbited around the nucleus in fixed shells.
-This prevents the atom from collapsing due to electrons being attracted to the nucleus if there were no shells.
Who discovered neutrons?
Chadwick discovered neutrons in 1932.
What is the atom?
Has a positively charged nucleus orbitted by negatively charged electrons.
What is the radius of a nucleus?
1 x 10-15m
What is the radius of an atom?
1 x 10-10m
Why is most of the atom’s mass in the nucleus?
Contains subatomic particles which are heavier than electrons.
What is density?
How much mass is contained within a certain volume.
What is the formula for density?
Density = Mass / Volume
Why do solids and liquids have similar, higher densities?
-Particles are arranged closely together due to electrostatic forces of attraction.
-The space between particles doesn’t change significantly.
-Liquids tend to have lower densities than solids but water is denser than ice.
Why do gases have much lower densities than solids and liquids?
-The spacing between atoms is much greater.
-Particles have a lot of energy to move so they occupy a greater volume and are less dense than solids and liquids.
Why does a higher density mean a higher pressure?
- There are more particles in the volume of space.
- There are more collisions between the particles.
- Collisions increase the pressure.
- Therefore a higher density means a higher pressure.
What is the conservation of mass?
Mass is conserved when a substance changed state therefore the substance’s volume will change, resulting in a different density, but the mass remains constant.