Y8:Chem7.1 Flashcards
(61 cards)
The solid sphere model is good enough to–, but it is not good enough to–
explain or predict state changes and the different properties of the substance in the three state
Explain or predict chemical reactions
analogy
A comparison between one thing and another to help to explain something
The new model explains—
How atoms join together and chemical reactions
Atoms are made out of tiny—
– make up the nucleus, –orbit outside the nucleus
charged sub-atomic particles (proton, neutron, electron)
protons and neutrons; electrons
Mass and charge of proton, neutron, electron
proton: 1; +1
neutron: 1; 0
electron: 1/2000; -1
Analogy for the size of an atom
If the atom is to be the size of a football stadium, the nucleus is the size of a pea at its center
Why do atoms have no net charge?
The number of protons is equal to the number of electrons.
An individual atom is hold together by the – between its — and —.
electrostatic attraction; positively charged nucleus; negatively charged electrons
In the 1800s, scientists took sealed tubes containing –. They set up an –.
Amazingly, the gases conducted electricity. One day, Johann Hittorf noticed a –. The glow, he said, was caused by –.
These were –.
tiny amounts of gas; electric circuit and applied huge voltages; green glow on the screen; rays from the negative electrode.
cathode rays
How to prove that cathode rays are made up of electrons (2)
- Cathode rays move towards a positive electrode, so they have a negative electrical charge
- pass cathode rays between electrically charged pieces of metal, the rays will change direction to bend towards the positively charged metal
Thomson’s model of an atom
An atom is a positively charged sphere. There are negative electrons embedded in the sphere.
Why is the plum pudding model wrong?
When Rutherford fired positively charged particles at a gold foil, some of them bound backwards. According to the plum pudding model, the particles should go straight through the foil because the positive charge in the foil was not concentrated enough to cause significant deflection.
Rutherford’s new model
- Atoms have a central nucleus. Most of the mass of an atom is in its nucleus. The nucleus is positively charged.
- A nucleus is surrounded by empty space in which electrons move.
Rutherford’s model’s explanation of his oberservations
The positive particles that bounce back hit a nucleus.
The positive particles that change direction a little pass closely to a positively charged nucleus.
The positive particles that went through the foil had passed the empty space between the nuclei.
The new state of matter
Another new boson
Bose-Einstein condensate: would only exist at very low temperatures
Higgs bosons: give other sub-atomic particles their mass
LHC
Lardon Hadron Collider
Purpose: to learn more about sub-atomic particles.
it is a circular tunnel, deep underground. It makes beams of high-energy protons. Inside the tunnel, huge magnets guide the protons around the circle, in both directions. The protons collide with each other. Scientists detect the particles made in the collisions.
an atom has an equal number of protons and electrons.
Particles in the nucleus- protons and neutrons - are called –. The total number of protons and neutrons in an atom is its –/–
It gives the – compared to other atoms.
nucleons; nucleon number/ mass number
relative mass of an atom
The different isotopes of an element have –.
different nucleon numbers
Tap water is -. It has other substances mixed with it, such as –.
not pure; chlorine and carbonates.
Pure silicon contains silicon atoms only. It is used to –.
make integrated circuits in phones
The purity of the water of the Arabian Sea is –. This means that –.
96.3%; In 100g of seawater, there is 3.7 g of salt and 96.3g of water.
Ibuprofen is a painkiller. The purity of the ibuprofen is - or better.
This means that 100g of the powder contains –.
98%; 98 g or more of ibuprofen
The - of the pure substance – while it melts, freezes, or boils.
temperature; does not change
