C1 Flashcards
What is a physical change?
When a substance changes state or shape or breaks into pieces
No new substances are made
Reversible
What is a chemical change?
Produces one or more new substances
Properties of the new substance are different from the original
Difficult or impossible to reverse
What happens to the particles in a physical (state) change?
Particles stay the same but arrangement and movement changes
What happens to particles in a chemical change?
Particles break up and join together in different ways
This is why new substances are made
What is the size of an atom?
3 x 10^-9m
What is the radius of a nucleus
1 x 10^-14m
What are electrostatic forces? (3)
Attractive forces between positive and negative charges in atoms
Forces are weaker the further apart from the particles
Strongest in solids, weakest in gases
Limitations of the particle model: (3)
Doesn’t account for:
- forces between particles
- size of particles
- space between particles
What is an atom?
The smallest particle of an element that still contains the chemical properties
What is a molecule?
Made from two or more atoms joined together joined by attractive forces called chemical bonds
What are the subatomic particles in an atom?
Protons
Neutrons
Electrons
What is the relative mass of the subatomic particles?
Proton = 1
Neutron = 1
Electron = 0.0005
What is the relative charge of the subatomic particles?
Proton = +1
Neutron = 0
Electron = -1
What is the atomic number?
Number of protons (and electrons) in the nucleus
What is the mass number?
Total number of protons and neutrons
What is an isotope?
Atoms with the same number of protons but with different numbers of neutrons
Same atomic number as element but different mass number
What are ions?
Charged particles
Formed when an atom loses or gains electrons
Can occur during chemical reactions
What did Dalton do?
Suggested all matter is made from atoms
- all atoms of an element are identical
- different elements contain different types of atoms
What did Thomson do & how?
Found that beams of cathode rays changed direction in electric and magnetic fields
Concluded that cathode rays were tiny negatively charged particles
- atoms contain electrons
- atoms are neutral overall
What did Rutherford do?
Tested the plum pudding model in 1909
Pointed beams of alpha particles at thin gold foil
Expected particles to go straight through, most did
Some changed direction and some came back
- atoms have a positively charged nucleus containing most of the mass
What did Bohr do?
Electrons occupy shells around the nucleus
