Chemistry Flashcards
How close together are the particles in a solid
Very close
How close together are the particles in a liquid
Quite close
How close together are the particles in a gas
Wide apart
How are the particles arranged in a solid
Ordered
How are the particles arranged in a liquid
Random
How are the particles arranged in a gas
Random
How do the particles move in a solid
Vibrate only
How do the particles move in a liquid
Move fairly freely
How do the particles move in a gas
Move freely
Why do liqiuds and gases take the shape of their container
Particles can move around
Why do solids not take the shape of their container
Particles cannot move around
Why can gases be squashed easily
There are big spaces between the particles
Why can’t solids and liquids be squashed easily
Particles are close together and can’t move
What is the change of state from solid to gas called
Sublimation
What is the change of state from gas to solid called
Deposition
What is the change of state from solid to liquid called
Melting
What is the change of state from liquid to gas called
Boiling
What is the change of state from gas to liquid called
Condensing
What is the change of state from liquid to solid called
Freezing
What are the differences and similarities between boiling and evaporation
Same: Change from liquid to gas
Difference:
Boiling: Boiling occurs at a set temperature, Occurs throughout the liquid, there’s bubbles.
Evaporation: can occur below b.p, only happens at the surface, there’s no bubbles
When ethanol is heated it boils at 78°C. Its temperature doesn’t rise while it boils. Explain why the temperature
does not rise even though the ethanol is being heated.
The energy is used to change state instead of increasing the temperature. It is needed to overcome forces between particles
What is in the nucleus of an atom
Protons and neutrons
What is in shells around the nucleus in an atom
Electrons
What is the relative mass of a proton
1
What is the relative mass of a neutron
1
What is the relative mass of an electron
1/2000
What is the charge of an proton
+1
What is the charge of a neutron
0
What is the charge of an electron
-1
How to calculate the number of each particle
The atomic numer, protons and electrons are always the same amount.
The number of neutrons is the mass number minus the number of protons
Why are atoms always neutral
The atoms of an element contain equal numbers of protons and electrons and so have no overall charge.
What are the rules of maximum amount of electrons in each shell.
1st: 2
2nd: 8
3rd: 8
4th: the rest
What is an isotope?
Different forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nucleus
What is formula mass
When 2 elements chemically combine to make a compound, the name of the 2nd elements name changes to - ide.
Magnesium + sulphur -> Magnesium Sulphide
How do you work out the formula mass
When we work out the formula Mass for a compound, we must add together the atomic masses of all the elements in the formula.
You must write the number as a subscript (like an indices but below the number).
Work out the formula mass for aluminium Sulphate
Al2(SO4)3
(2xAl) + [(1xS) + (4xO)]3 (2x27) + [(1x32) + (4x16)]3 (2x27) + (32+64)3 54 + (96) x 3 54 + 288 = 342
How many elements are there
118
92 natural
26 man-made
What is a mole
A mole is just a number
A mole is 6.022 x 10^23
1g is a mole of hydrogen which has a relative formula of 1.
For example water has a relative formula mass of 18 and a mole of water is 18g. This means that that 2 moles of water equals 36g.
How to work out the number of moles
Number of moles = mass of substance divided by relative formula mass.
What is avogadro’s number
6.02 x10^23
How to work out the number of particles
Number of particles = number of moles x 6.02 x 10^23
How to find the percentage of an element in a compound
Percentage of an element in a compound = mass of element in compound divided by relative formula mass of compound x100
