C1 - Particles Flashcards
What do chemists mean when they use the term particles?
Atoms, ions or molecules
What is the arrangement of a solid?
regular
what is the arrangement of a liquid?
random
what is the arrangement of a gas?
random
what is the relative distance between solid particles?
very close
what is the relative distance between liquid particles?
close
what is the relative distance between gas particles?
far apart
what is the main movement of solid particles?
they vibrate around fixed positions
what is the main movement of liquid particles?
they move around each other
what is the main movement of gas particles?
they move quickly in all directions
can you compress a substance in its solid state?
no
why can you not compress a solid or liquid substance?
there is no space for the particles to move into
why do substances in a solid state have a fixed shape?
since it’s particles vibrate around fixed particles and cannot move from place to place
Give 3 examples of chemical changes
- cooking eggs
- steel rusting
- wood burning
- acid + alkali
Give 3 examples of physical changes
- freezing juice to make a lolly
- mixing sand with water
- dissolving sugar in water
What happens to a substance when it changes state?
The substance’s particles stay the same but the movement and arrangement changes
What happens to a substance’s particles during a chemical reaction?
Particles break up and join in different ways
new substances are made
What is the smallest particle that makes up a substance?
atoms
What element has the smallest atom?
Helium atoms
what is the equation to calculate the mean distance between atoms?
distance between atoms
————
diameter of atom
What are the forces between particles called?
Electrostatic forces
State three limitations of the particle model
- unable to see the electrostatic forces
- unable to see the size of particles
- unable to the the space between particles
Why does the volume of a substance increase when it melts?
Some of the forces of attraction are overcome and so the particles can move around each other
describe what happens to the particles of a substance in the liquid state as it cools down but remains in the liquid state
- particles transfer energy its surroundings
- the particles slow down
- some some electrostatic bonds form between them
describe what happens to the particles of a substance in the liquid state as it freezes
- energy transfers to its surroundings
- the particles become regularly arranged
- the particles can no longer move around each other
- more electrostatic bonds form between each other
State one way in which the diagram does not accurately model the arrangement of particles
show them as stationary, and very close
what is an atom?
the smallest particle of an element that still has its chemical properties
what is a molecule?
- two or more atoms joined together
what is a bond length?
the distance between the centres of two joined atoms
what does the atomic number tell us?
how many protons there are in the atom
what is the mass number?
total number of protons and neutrons
what is an isotope?
- an atom of the same element with the same number of protons and electrons, but a different number of neutrons
- same atomic number
- different mass number
what do the chemical properties of an element depend on?
the number of electrons in the atom
what is an ion?
- a charged particle
- formed when atoms (or groups of atoms), lose or gain electrons
how did dalton contribute to the development of the atomic model?
- all matter is made from atoms
- different elements have different atoms
- same elements have identical atoms
what is a chemical bond?
an attractive force which keeps two atoms bonded together
How did rutherford’s results change as he increased the deflection angle (and why?)
- The number of particles deflected decreased
- as the particles were not being shot straight to the middle (where the nucleus was), and instead at the side where it was empty space
Charge of an alpha particle?
Positive, +2
What Electromagnetic radiation is emitted by electrons?
Photon
What is the typical diameter of atoms and small molecules?
0.1nm
Define atomic number
The number of protons in the nucleus of an atom
What properties do isotopes affect and don’t affect.
May Affect physical properties - due to different numbers of neutrons.
Do not affect chemical properties - number of electrons the same.
What experiment did JJ Thompson do? What did he find? What did he have to make sense of?
He found that beams of cathode rays changed direction in electric and magnetic fields - he concluded that cathode rays were tiny particles that were negatively charged and much smaller than atoms.
He had to make sense of two observations:
- atoms contain electrons
- atoms are neutral overall
