Topic 7- Matter Flashcards
Density definition
A mass per unit volume as a measure of ‘compactness’ of a substance.
Symbol for density
Rho (slanted p)
Density equation
Mass/volume
Density units
G/cm cubed
Kg / m cubed
How does a solid float?
If it has a lower average density than the fluid.
How do you find the density of a substance?
For a liquid: Use mass balance to measure mass of empty measuring cylinder.
Pour in liquid and measure mass again (mass difference=liquid mass).
Measure liquid volume on cylinder (1ml = 1 cm cubed).
For solid, work out volume by dimensions.
How do you measure the density of an object without a regular shape?
Measure mass w mass balance.
Fill bottle w liquid of known density.
Place stopper on and dry outside, measure mass of bottle.
Empty bottle and place object into density bottle w same liquid.
Calculate volume of displaced water by taking the mass of the bottle with the object in and taking away the object’s mass, showing volume of water filling it. Take this away from the original mass of the bottle with just water in to find the displaced water mass, (1ml=1cm cubed). This shows the vol.
Physical changes
Only the form of substance changes
Chemical changes
New substances are created by reaction.
Solid
Strong forces of attraction hold particles in close, fixed, regular arrangement. Particles have little energy in kinetic energy stores so vibrate about fixed positions.
Liquid
Weaker forces of attraction between particles which are close together but can move past each other and form irregular arrangements. Have more energy than solid so move in random directions at low speeds.
Gas
Almost no forces of attraction, most energy in kinetic stores, travel in random directions at high speeds.
Where is the energy in a substance’s thermal energy store held?
By its particles in their kinetic energy stores.
Temperature in kinetic theory
Way of measuring average internal energy of a substance.
Specific heat capacity
The change in energy in the substance’s thermal store needed to raise the temperature of 1kg of that substance by 1°C.
Equation relating mass, energy, specific heat capacity and temperature
Change in thermal energy= mass * specific heat capacity* temp change
What’s specific heat capacity measured in?
J/kg°C
How do you find the specific heat capacity of water?
Measure mass of insulating container w mass balance.
Fill w water and measure mass again (difference=water mass)
Connect joulemeter (at 0) to immersion heater in water w thermometer w lid on container.
Measure temp of water and turn on power.
When temp as increased by set temp, record energy on joulemeter
Practical to show energy used in breaking intermolecular forces and energy produced in forming intermolecular bonds
Fill beaker w ice and thermometer (measure temp of ice)
W Bunsen, heat gradually and record temp every 20 secs and state of ice
Continue until begins to boil
Plot graph
Specific latent heat
Amount of energy needed to change 1kg of a substance from one state to another without changing its temperature.
Specific latent heat for cooling
Energy released by a change in state
Specific latent heat for changing between a solid and a liquid
Specific latent heat of fusion
Specific latent heat between liquid and a gas
Specific latent heat of vaporisation
Equation linking thermal energy, mass and specific latent heat
Thermal energy = mass * specific latent heat
What’s specific latent heat measured in
J/kg
Relationship between pressure and volume
Inversely proportional
P1V1 = P2V2
Absolute zero
-273°C
Start of Kelvin scale
Conversion from °C to kelvin
+273
Gas pressure
The total force exerted by the particles per unit area
