P1 - Matter Flashcards
What did dalton think?
All the atoms in an element are the same
The atoms in one element are different from the atoms in all other elements
What did Thomson think?
Used cathode ray investigations given out by hot metals
An atom contains negative electrons
Plum pudding model
Overall , atoms have no electrical charge -neutral
What did Rutherford think?
An atom is made of a tiny , positively charged nucleus with electrons around the outside.
All mass in nucleus.
When alpha particles hit a nucleus, they bounce back
Nucleus = protons and neutrons
What did Bohr think
Electrons can only move in fixed orbits called electron shells, around the nucleus
Diameter of atom?
10^-10
Radius of nucleus
10^-15m
What is the formula for density?
Density (kg/m^3) = mass (kg) / volume (m^3)
How to measure density of different objects?
Eureka can which is a tin with spout off the side
Fill up with water
Make sure water is above the spout
And let the water run down until no more water runs out
Then use a measuring cylinder underneath the spout
Place the object inside and however much water comes out is the volume of the shape.
Then measure with balance.
And use density equation
Explain the density of a solid?
There are more particles closely packed together.
The more particles, the greater the mass
Therefore density increases
What is the law of conservation of mass?
Particles can neither be created nor destroyed
Happens in a closed system
Difference between energy and temperature?
Temperature is how hot or cold something is , measure with thermometer.
Units is °C or °K - usually tells the average kinetic energy of particles
Energy in a thermal stall is measured in Joules (J)
Depends on the arrangement of the particles and how fast they move
What happens when you heat things up?
- Change the energy store- Increase in temperature
- Change in state
- Chemical reactions occur
What is a physical and chemical change?
Physical change is a change of state , e.g. solid to liquid
New substances are not made therefore change is reversible
Chemical change involves a chemical reaction
New substances are made therefore change is irreversible
What is specific heat capacity?
Amount of energy needed to raise the temperature of 1kg of material by 1°C.
Units - (J/kg°C)
What are the three things that determine the amount of energy we need, to raise the temperature of an object?
- Type of material
- Mass of material
- Temperature rise
What is the practical to determine specific heat capacity?
Beaker with water
Immersion heater connected to power supply
Thermometer
Insulation
Measure the change in temperature . The mass of water is known.
Use the equation to work out the SHC of the substance or the energy.
What does an object with high specific capacity mean?
It is resistant to change in temperature.
What does it mean if an object has low specific capacity?
It heats up very quickly
E.g. saucepans
What is the specific latent heat of fusion?
The energy transferred when one kg of the substance changes from the solid state to the liquid state.
Vice versa
What is the specific latent heat of vaporisation ?
Energy transferred when 1 kg of substance changes from the liquid state to gas state
Explain gas pressure with the idea of a balloon
As you blow into the balloon there is an increase number of air particles inside.
Particles collide with the surface
Each collision creates a force
All the forces created by the collisions is the gas pressure
What happens if we add more air particles to a container that can’t expand
Gas pressure increases rapidly
What happens if temperature of a gas is increased
Gain kinetic energy
Therefore more frequent collisions
Leading to increase in pressure
How to measure pressure?
Use a pressure gauge
Units for pressure is (Pa)
1kPa = 1000Pa
What would happen if we call the gas down to absolute zero?
It would have zero Pa of pressure
We do this by extrapolating a graph of results
What is the proportion of pressure and volume?
Pressure and volume are inversely proportional
If the volume doubles, the pressure will halve.
How can we increase the internal energy of a gas?
1) Heat it
2) Doing work on it
Explain how a bike pump works in terms of pressure?
When the user applies force to the pump the gas gets hotter.
Kinetic energy increases so more frequent collisions
Pressure increases
What is atmospheric pressure?
The gases that make up the atmosphere exert atmospheric pressure.
What is the pressure on the surface of Earth?
100,000Pa
Explain pressure in terms of a can
Use a open can
The forces acting in all directions are equal
If air is removed the can collapses
This is because the only pressure acting is from the outside so it collapses
What happens to atmospheric pressure as you go up?
As you go away from the surface of the Earth then atmospheric pressure decreases
Because there is fewer particles of air pushing down
What does the pressure gauge read?
The atmospheric pressure
Not zero
What happens to liquid pressure as you go deeper?
Pressure increases
More particles are pressing down from above
What happens to pressure if liquid is denser?
Greater pressure at the same depth as in a less dense liquid
Explain why in a water bottle with three punched holes , the bottom one pushes water out the furthest?
There are more water particles above and therefore more pressure
Why do items float?
Items will float when upthrust balances weight . Equal forces.
What is the formula for pressure?
Pressure (Pa) = force(N) / area (m^2)
Explain how a submarine can go different depths at sea?
It has tanks which can either be filled with air or water.
If submarines want to be lower, allow water in , as this increases the weight. Weight is greater than upthrust.
If submarines want to be higher, push air in, this increases upthrust. Upthrust is greater than weight.
