Topic 11 - Particle Model, Forces of Matter Flashcards
kinetic theory
everything is made of tiny particles
explain a solids arrangement, movement and properties
- forces of attraction hold particles closely together -> the particles can vibrate in a fixed position
- this explains why solids keep their shape and cannot be compressed
explain a liquids arrangement, movement and properties
- the particles are moving faster and so the forces of attraction between the particles are not strong enough to hold them in fixed positions
- the particles can move past each other so liquids flow and take the shape of their container
- particles are still very close together, so liquids usually can’t be compressed.
explain a gases arrangement, movement and properties
- the particles are far apart and moving around quickly
- compressible
- expand to fill their container
what happens to the particles when a substance undergoes a change of state (arrangement & mass)
- end up in a different arrangement
- same number of particles so the mass stays the same (mass is conserved)
-> physical change, because no new substances are formed and the substance recovers its original properties if the change is reversed
density
The mass of a certain volume of the substance
when are the substances the most dense
when they’re solid because the particles in solids are close together
density equation
density = mass (kg)
volume (m3)
CORE PRACTICAL - Investigating densities method
Liquid:
- Put an empty beaker on a balance, and set the balance to zero.
- Use a measuring cylinder to measure 50 cm of a liquid and then pour it into the beaker. Write down the reading on the balance. This is the mass of 50 cm’ of the liquid
Solids:
- Find the mass of the solid and write it down
- Stand a displacement can on the bench with is spout over a bowl
- Fill it with water until the water just starts to come out of the spout
- Hold a measuring cylinder under the spout and carefully drop your object into the can. If your object floats, carefully push it down until all of it is under the water. Your finger should not be in the water.
- Stand the measuring cylinder on the bench and read the volume of water you have collected. This is the same as the volume of your object. Write it down.
thermal energy
Energy transferred to a system by heating will be stored in the movement of the particles that make up the substances in the system
what happens to the vibrations in a solid when the solid stored more thermal energy
vibrations increase
temperature of a substance
measure of the movement of the particles due to energy stored
how to maintain a store of thermal energy
The amount of energy that is transferred to the surroundings by heating needs to be reduced -> this can be done by surrounding the warm objects with insulation interiors such as wool, foam or bubble wrap
What does the amount of thermal energy stored in something depend on?
- It’s temperature
- It’s mass
- the material it is made from
specific heat capacity of a material
amount of energy it takes to increase the temperature of 1kg of a substance by 1°C
how does temperature cause change of state
When enough energy is transferred to solid it reaches its melting point; if energy continues to be transferred, the temperature stops rising because the extra energy is used to overcome the forces between the particles and turn the solid into a liquid
specific latent heat
Amount of energy it takes to make 1kg of a substance change state
change in thermal energy equation
change in thermal equation (J) = mass (kg) x specific heat capacity (J/kg °C) x change in temperature (°C)
Thermal energy needed for a change of state equation
Thermal energy needed for a change of state (J) = mass (kg) x Specific Latent heat (J/kg)
CORE PRACTICAL - Investigating water method
Melting ice:
- boiling tub full of crushed ice into a heatproof beaker put a thermometer in the ice and note the temperature
- Put the beaker onto a tripod and gauze, pour hot water from a kettle into the beaker and keep it warm using a Bunsen burner
- Measure the temperature of the ice every minute, record your results in a table, stop taking readings three minutes after all the ice is melted
- note the times at which the ice starts to melt and when it appears to be completely melted
Specific heat capacity:
- put a polystyrene cup in a beaker onto a battery powered balance and zero balance then fill the cup almost to the top with water and write down the mass of water, carefully remove the cup from the balance
- put a thermometer in the water and support it, put a 12 V electric immersion heater into the water making sure the heating element is completely below the water level, connect the immersion heater to a joulemeter
- Record the temperature of the water and then switch the immersion heater on, stir the water in the cup gently using the thermometer
- After five minutes, record the temperature of the water again and also write down the readings on the joulemeter
What is the measure of the temperature of a gas?
The temperature of a gas is a middle of the average kinetic energy of the particles in the gas
-> force of the average speed of the particles higher the temperature
What increases the kinetic energy of the particles in a gas?
Heating a gas increases the kinetic energy of the particles so they move faster and the temperature rises
pressure of a gas
due to the forces on the walls of a container caused by the moving particles hitting the walls
What happens to the pressure if the particles are moving faster?
The faster the particles are moving more frequent the collisions will be and the more force they will exert when they collide increasing pressure
How does an increase in temperature of a gas have an effect?
Increase the temperature of a gas increases the speed of the particles and so it also increases the pressure of the gas
Units for pressure
pascals (Pa)
absolute zero
The temperature of -273°C (coldest point on the thermometer temperature scale)
What happens to the pressure if the gas’ temperature was absolute zero
It’s pressure would be zero and the particles will not be moving
Kelvin Temperature scale
Measures temperatures relative to absolute zero
Units for the Kelvin temperature scale
Kelvin (K)
How do you convert from kelvin to degrees Celsius?
Subtract 273
How do you convert from degrees Celsius to kelvin?
Add 273
How did the kinetic energy to the particles in a gas correlate to the Kelvin temperature of the gas?
They’re directly proportional
Gas Pressure
The effect of gas particles hitting the surface, cause a net force on the surface which acts at a right angle to the surface
Equation for the volume and pressure of a fixed mass of gas at a constant temperature
P1 x V1 = P2 x V2
-> product of the starting pressure and the starting volume is equal to the product of the final pressure and the final volume
How does a bicycle pump get warm every time you push the pump handle?
The force is transferring energy to the gas inside the pump so the speed of any particles inside the pump will increase once they bounce off; the average speed of the particles inside the pump will increase and we detect this as an increase in temperature
if a material is inelastic
They will keep their new shape and not returned to its original shape after the forces are removed
Can an object become inelastic if the force is too big
Objects are elastic when the force is a small but behave in elastically if the forces are too big
Extension of a spring
The change in length when forces are applied
What is a force and length graph for a spring?
What is the extension of force graph like for a spring and rubber band?
spring constant
The force needed to produce the extension of 1m in a spring
What was the equation for force using extension and spring Constant
Force (N) = spring constant (N/m) x extension (m)
energy transferred in stretching equation
Energy transferred in stretching (J) = 0.5 x spring constant (N/m) x extension squared (m2)
Method for the core practical: investigating springs
- set up the apparatus shown the photo; the zero on the ruler should be level with the bottom of the unstretched spring
- Measure the length of the spring with no weight hanging on it and write it down
- Hang a 1 Newton weight on the spring; record the extension of the spring
- Repeat the last step until you found the extension of the spring with 10 different masses
- Repeat all the steps for a different spring
- Use your results to calculate the sprint constant for each spring
In terms of area when is pressure less?
When there is a larger area, the pressure is less
pressure
A measure of the force on a unit of surf area where the force is normal to the surface
Pressure equation
Pressure (Pa) = force normal to the surface (N)
area of surface (m2)
What does the pressure exerted by a fluid depend on?
- The depth of the fluid -> the deeper you are the more weight of fluid there is above you to exert pressure
- The density of the fluid
What happens to the pressure if you go up a mountain?
The air pressure decreases because there is less air above you
How does the pressure of fluids act on a person?
Acts normal to any surface (right angle)
Pressure due to a column of liquid equation
Pressure due to a column of liquid (Pa) = height of column (m) x density of liquid (kg/ms3) x gravitational field strength (N/kg)
Why do fluids have upthrust?
This force is due to the difference in pressure above and below the object
Pressure difference equation
Pressure difference = depth difference x density of liquid x gravitational field strength
What is the upthrust of a liquid equal to?
The weight of the water displaced
What is the atmospheric pressure?
100,000 Pa
