Topic 14- Particle Model Flashcards
How are particles arranged and move in different states?
Solid- uniform+ vibrate
Liquid- shape of container at bottom + movement
Gas- shape of container + fast movement in all directions
not enough energy to overcome forces of attraction
Density =
Mass/ volume
What is the calculation for pressure?
Pressure= force/ area
Core practical: investigate the density of a solid and liquid
Solids:
1) Fill eurika can with water
2) Add solid
3) Measure water displaced = volume of shape
4) Weigh shape for its mass
5) Use mass/volume=density
Liquids:
1) Place measuring cup on balance on zero
2) Add water
3) Find mass
4) Find volume
5) Mass/volume= density
Why does a solid have higher density than a gas?
-Gases= less dense as particles are more spread out + move more freely + collide and move opposite way
What are physical changes in substances?
Mass is conserved but physical state changes
Can be reversed so is different to most chemical reactions
What happens when you heat a system?
Change the energy stored and thus the substance stored more energy and will have to change dtate
What is specific heat capacity?
Heat needed to raise 1kg of a substance by 1•C
What is specific latent heat?
Heat energy needed to change the state of 1Kg of a substance (end of liquid to start of gas)
What is the equation for specific heat capacity?
Change in thermal energy= mass (kg) x specific heat capacity x temp change
∆Q = m×c×∆θ
What is the equation for thermal energy needed for a change in state?
Thermal energy needed= mass (kg) x specific latent heat
Q = m× L
How to reduce unwanted energy loss?
Thermal insulation:
-Prevents heatloss
-Loft insulation
-Cavity wall (air)
-Double glazed windows
-Reflexive foil behind radiators
Core Practical: Investigate the properties of water by determining the specific heat capacity of water and obtaining a temperature-time graph for melting ice
1) Place polysterine cup in beaker
2) On balance+ to zero
3) Add known water
4) Fully ubmerge immersion heater
5) Attach to joulemeter
6) Take start temp
7) Turn on immersion heater
8) Wait
9) Record end temp of middle of water
use
∆Q = m×c×∆θ
What is pressure in a gas?
-Random particle collisions with the walls of the container
How does increasing temperature increase pressure?
-Particles have more energy thus move faster
-Collide more frequently and energetically with container’s walls
at a fixed mass and volume
What is absolute zero?
- Lowest theoretical temperature
- -273 degrees celsius
- 0K
- Particles emmit no heat energy
- Lowest energy state
Kelvin to celsius?
K=C+273
What is Boyl’s law?
-If temp is constant
-Increasing pressure will compress the gas
decrease= expandeed
Where does the pressure exert force?
-90 degrees from the surface
How does changing gas volume affect its pressure?
diff container
-Smaller= higher pressure as walls are hit more often
same mass and temp
Equation for pressure and volume at constant temp?
P1xV1=P2XV2
How does doing work on gas increase its temperature?
-Smaller volume
-Higher pressure
-More collsisions
-Faster movement (more KE)
-More heat energy
e.g bike pump
Why is there higher pressure deeper in a fluid?
-Fluid above compresses fluid further down
-More tightly compact as weight pf fluid above
How to work out pressue in a fluid?
Depth x density x gravitational field strength
How does pressure vary in the atmosphere?
-Decreases the higher you go
-Warmer near earth
-Lower density higher
What is upthrust?
-Upwards force on an object in a fluid
-Cuased by higher no.of particle collisions on the bottom of an object (at 90 degrees)
When do objects stop sinking in a fluid?
When its weight and upthrust are balanced
Upthrust=
Weight of the fluid displaced
How does the weight of the object differ further down in the fluid?
-Increases
-Weight of water above it
Why do objects sink?
-If they are more dense than the fluid
Do all objects have upthrust?
-Yes
-But weight and density affect it
Why do boyant objects get harder to push down in a fluid the deeper?
-More dense
-More pressure
-More upthrust
