P1 Flashcards
What is the Law of Conservation of Mass?
Mass is neither created nor destroyed in chemical reactions. The mass at the beginning of a reaction will equal the mass at the end of a reaction.
What is the formula for density?
Density = mass ÷ volume
What were John Dalton’s beliefs about the atom?
1 - that all atoms in an element were the same.
2 - the atoms in one element are different from the atoms in all other elements.
What did J.J. Thompson discover and when? What was his particle model called?
In 1897, J.J.Thompson discovered the electron and reasoned that it must have a negative charge. He believed that:
- all atoms were neutral overall (no electrical charge)
- atoms contained negative electrons.
His model was called the plum pudding model.
Who aided Ernest Rutherford in his work?
Hans Geiger and Ernest Marsden.
What was Rutherford’s experiment?
He fired postively-charged Alpha particles at a sheet of gold foil, expecting them to pass straight through.However, while most passed through, others were repelled entirely and some changed direction upon making contact. This lead Rutherford to suggest that atoms were a positively-charged mass surrounded by empty space and orbiting electrons.
What did Neils Bohr’s model of the atom change?
It changed the electron orbits onto electron shells, as the orbits would have meant that the electrons spiralled inwards until colliding with the nucleus.
Give two ways of measuring temperature.
1 - with a thermometer
2 - with a temperature sensor
What is a kelvin (K) a unit of measure for?
Temperature.
What is the difference between the energy in a thermal store and the temperature?
The energy in a thermal store is a measure of how fast the particles are moving or vibrating.
Temperature tells you about the average kinetic energy of the particles.
What is the difference between a chemical change and a physical change?
Physical - usually reversible. Does not involve the formation of a new substance, as particles are simply rearranged. E.g. Dissolving.
Chemical - Usually irreversible. Involves the formation of a new substance as atoms chemically bond together.
State the unit of energy.
Joules (J)
Give the formula for the change in thermal energy.
change in thermal energy = mass x specific heat capacity x change in temperature
Define specific heat capacity.
The energy needed to raise the temperature of 1kg of a material by 1K.
State the unit for specific heat capacity.
J/kgK
Give the formula for specific heat capacity.
specific heat capacity (J/kgK) = change in thermal energy (J) ÷ (mass (kg) x change in temperature (K) )
What does a low specific heat capacity indicate?
It shows that the material is not very resistant to changed in temperature, meaning that it will heat up quickly. These sorts of materials are useful in cooking appliances.
State the unit for specific latent heat.
J/kg
Give the formula for specific latent heat.
SLH (J/kg) = thermal energy required for a change in state (J) ÷ mass (kg)
What are the two versions of specific latent heat?
Fusion and vaporisation.
What is the SLH of fusion?
The energy transferred when 1kg of a substance changed from solid state into a liquid state, or from liquid state into the solid state.
What is the SLH of vaporisation?
The energy transferred when 1kg of a substance changed from liquid to gas.
What is the difference between specific heat capacity and specific latent heat?
Specific heat capacity is about a change in temperature, while specific latent heat is about change in state.
State the units for pressure.
Gas pressure: Pascals (Pa)
N/m^2 (Newtons per metres squared)