Solid, liquids and gases Flashcards
1
Q
name the units for temperature
A
- degrees Celsius
- degrees Kelvin
2
Q
name units for density
A
- Kg/m3
- g/cm3
3
Q
name the unit of pressure
A
- N/m2
- 1N/m2 = 1 Pa (pascal)
- N/cm2
4
Q
name the unit for area
A
m2
5
Q
name the unit for weight
A
N = newtons
6
Q
name the unit for speed
A
meters/ second = m/s
7
Q
name the unit for energy
A
J = joules
8
Q
name the units for mass
A
- kg
- g
9
Q
name the units for distance
A
m = meters
10
Q
how many cm2 are in 1m2
A
1m2 = 10,000cm2
11
Q
define density
A
the mass per unit volume of material
12
Q
formula for density
A
density (rho) = mass (m) / volume (v)
13
Q
objects made of the same materials have….? why is this?
A
- objects of the same material have the same density, regardless of their mass
- this is because, if both mass and volume increase proportionally, then density remains constant
14
Q
describe and explain the characteristics of objects with low density
A
- objects of lower density have a smaller number of particles in the same volume
- this means that particles are more spaced out
- this causes the object to have a lower mass
15
Q
describe and explain the characteristics of objects with high density
A
- objects with high density have a greater number of particles in the same volume
- this means that particles are closer together
- this causes the object to have a higher mass
16
Q
substances that are less dense ….. on more dense substances
A
substances that are less dense float on more dense substances
17
Q
formula for volume of a sphere
A
v = 4/3 x pi x r3
18
Q
formula for volume of cube/cuboid
A
v = l x w x h
19
Q
formula for volume of cylinder
A
v = pi x r2 x l or h
20
Q
describe a method for calculating the density of a regular object e.g a cuboid
A
- using a ruler or vernier calipers, measure the side lengths of the shape = repeat 3 times and take an average of each length
- then use v = lwh to calculate the volume of the object
- measure the mass of the object on a digital balance that has been zeroed and set on a flat surface = repeat three times and take an average mass
- use the formula density = mass/volume to calculate the density using the average mass value and average volume value
21
Q
describe a method for calculating the density of a regular object e.g a rock
A
- fill a eureka can to just beneath the spout with water and place a measuring cylinder beneath the spout
- measure the dry mass of the rock on a digital balance that has been zeroed and set on a flat surface - take 3 repeats and take an average mass
- then gently lower the rock into the eureka can to prevent any splashing
- measure the volume of displaced water in the measuring cylinder which is = to the volume of the rock
- ensure to read the value off the cylinder at eye-level to prevent a parallax error
- take three repeat readings of volume by repeating process three times (but allow rock to dry before each repeat)
- use formula density = mass/volume to calculate the density using the average values of mass and volume
22
Q
describe a method for calculating the density of a liquid
A
- place a measuring cylinder onto a digital balance set on a flat surface and zero it
- then pour in a specific volume of liquid and measure volume by reading off cylinder at eye-level to prevent parallax error
- take three repeats of mass and volume and calculate an average value for each
- for volume ensure that the measuring cylinder is replaced with a dry one in each repeat to ensure an accurate value is produced
- using the average values of mass and volume, calculate density using density = mass/volume
23
Q
what is a systematic error? what is a random error?
A
- SE = error that occurs the same way in each repeat due to faulty equipment of flawed method, causing measurements to consistently be too high or low
- RE = error that occurs unpredictably each time a measurement is taken, often due to human reaction time or small environmental changes
24
Q
describe some possible systematic errors when calculating the density of an object
A
- balance not zeroed before taking a reading = too high
- using wrong units and converting incorrectly - e.g using kg/cm3
- not using dry mass of object in eureka can each repeat = too high
25
describe some possible random errors when calculating the density of an object
- reading meniscus of water in measuring cylinder from slightly diff angles each repeat = small variations in volume measurement
- dropping object into eureka can from diff heights each time = small variations in volume depending on how much water splashed out of eureka can
26
describe the arrangement of particles in a solid
- arrangement = close together in fixed positions
- bond strength = strong
- relative density = high
- motion = vibrating
- compressible = no
- flows = no
- fills space = no
27
describe the arrangement of particles in a liquid
- arrangement = close together in random positions
- bond strength = moderate
- relative density = high
- motion = moving at random velocities in random directions
- compressible = no
- flows = yes
- fills space = fills base
28
describe the arrangement of particles in a gas
- arrangement = far apart in random positions
- bond strength = weak
- relative density = low
- motion = moving at random velocities in random directions
- compressible = yes
- flows = yes
- fills space = fills whole space
29
which states of matter have the highest medium and lowest energy in their particles?
- solid = lowest
- liquid = medium
- gas = highest
30
why can gasses be compressed?
- there are large gaps between particles
- this means it is easier to push particles together
- so gasses can be compressed
31
where is the energy of a system stored?
the energy of a system is stored in its particles as internal energy
32
what is internal energy?
the collective kinetic energies of all the particles in a substance + the collective potential energies of all the particles in a substance
33
what happens when a system is heated?
- heating a material increases its internal energy
- this can only do one of two things - increase kinetic energy = increase temperature of material OR increase potential energy = particles are provided with energy to overcome forces of attraction that hold them together (weaken/break bonds)
34
what happens when kinetic energy of a material increases?
- when kinetic energy increases, internal energy increases
- an increase in internal energy requires only one of kinetic or potential energy to increase
- this increases temperature of the substance as temp is a measure of average kinetic energy of particles in a substance
35
what is directly proportional to the kinetic energy of particles?
temperature is directly proportional to the kinetic energy of particles
36
what happens when the potential energy of a material increases?
- when potential energy increases, internal energy increases
- an increase in internal energy requires only one of kinetic or potential energy to increase
- particles are provided with energy to overcome forces of attraction that hold them together (weaken/break bonds)
- this causes a state change as the particles' arrangement has changes
37
what remains constant during a state change and why?
- temperature always remains constant during a state change
- the energy transferred is used to break or form bonds between particles, not to increase their kinetic energy
38
describe the changes that occur when a solid melts to form a liquid
- particles gain energy and vibrate faster
- the forces between particles weaken, allowing them to move around at random velocities in random directions (but are still close together)
- the solid becomes a liquid, but the temperature stays constant during melting
39
describe the changes that occur when a liquid boils to form a gas
- happens at a specific temperature (boiling point) when heat is constantly supplied
- occurs throughout the liquid.
- particles gain more energy and move fast enough to overcome all intermolecular forces
- bubbles of gas form inside the liquid and rise to the surface as they are less dense than the liquid
- gas escapes at surface when bubble pops
- temperature stays constant during boiling
40
describe the changes that occur when a liquid evaporates to form a gas
- evaporation happens only at the surface of a liquid
- it occurs at temperatures below the boiling point
- particles in a liquid have a range of kinetic energies
- some surface particles have enough energy to completely overcome intermolecular forces and escape as gas
- no constant heat supply is needed — it can happen naturally if particles have enough energy
- as high-energy particles escape, the average kinetic energy of the liquid drops, so the liquid cools down
- evaporation has a cooling effect (e.g. sweat)
- then the cycle continues until the whole liquid evaporates
41
name the factors affecting evaporation
- temperature
- surface area
- humidity
- wind speed
42
how does temp affect evaporation?
- increased temp = increased kinetic energy
- this means more particles on the surface will have enough energy to completely overcome all intermolecular forces and escape as a gas
- this increases rate of evaporation
43
how does surface area affect evaporation?
- larger surface area = more particles with enough energy to completely overcome all intermolecular forces are able to escape as a gas at one time
- this increases rate of evaporation
44
how does humidity affect evaporation?
- increased humidity = air is already saturated so there is no space for particles to evaporate into
- this decreases rate of evaporation
- decreased humidity increases rate of evaporation
45
how does wind speed affect evaporation/
- higher windspeed = saturated air from evaporating particles is blown away from directly above the liquid surface
- this means that evaporating particles have more space to move into
- this increases rate of evaporation
46
describe a practical to obtain a temperature-time graph of a substance changing its state
- place stearic acid in a beaker with a thermometer and heat it to 80°C
- then record the initial temperature and the initial state
- record the temperature and state regularly every 30s
- continue even when state is changing, during which u will obtain a constant temperature
- continue this until the stearic acid reaches 45 degrees Celsius
- record the final state of the stearic acid
- plot a temperature (y-axis) time (x-axis) graph of results
47
when and why are there plateaus on a temperature-time graph?
- there are plateaus on a temperature-time graph when there is a state change
- this is bc temperature remains constant during a state change
48
why is the gradient the steepest at the start of a temperature-time graph demonstrating the cooling of a substance?
at the start, there is the greatest difference in temperature between the hot substance and surroundings, which causes the greatest transfer of thermal energy to the surroundings, resulting in a steep negative gradient at the start of a T-T graph of a cooling substance
49
what is specific heat capacity? what are the units?
- the amount of energy required to raise the temperature of 1kg of a substance by 1°C per kilogram of mass
- units = J/kg°C
50
formula for specific heat capacity
change in thermal energy (Q) = mass (m) x SHC (c) x change in temperature (theta)
51
what is the relationship between a material's SHC and amount of energy required to increase its temp?
the larger a material's specific heat capacity, the greater the amount of energy required to increase its temperature
52
what is the specific heat capacity of water?
4200 4,200 J/kg°C
53
describe a method for calculating the specific heat capacity of a metal block
- measure the mass of the metal block using a digital balance (zero it first) that's been set onto a flat surface - do 3 repeats and take an average
- insert a thermometer and heater into the block, and wrap it in insulating material to prevent heat loss by radiation and place on heatproof mat for same reason
- connect the ammeter in series and the voltmeter in parallel to the heater
- record the initial temperature of the block
- turn on the heater for a known time (t) using a stopwatch, then record the final temperature
- calculate the energy supplied using: E = P × t or E = V × I × t (where P = V × I)
- energy supplied = change in thermal energy (assume all energy supplied is transferred to block)
- calculate the specific heat capacity using: change in thermal energy = mass x SCH x change in temperature
- the identity of the metal can be obtained from its SHC as each metal has a diff SHC
54
systematic errors in SHC practical
- digital balance not zeroed before each repeat = mass consistently too high
- heat may be lost to surroundings by radiation = final answer is an overestimate
55
random errors in SHC practical
- if SHC of liquid is meausured, then liquid not stirred consatntly to ensure the temp measured is the temp throughout the fluid
- when voltage and/or current are changing between two values, be consistent in picking the higher or lower value for both
56
define pressure and give the units
- the amount of force per unit of area
- units = N/cm2 or N/m2
- 1 Pa (pascal) = 1N/m2
57
formula for pressure
pressure (p) = force (F) / area (A)
58
if the force is the same, pressure is greater....
- if the force remains constant, pressure is greater if the force is exerted over a smaller area
59
describe what effect sharpening a knife has on the pressure it exerts onto food
- sharpening a knife reduces the area it is in contact with the food
- this causes an increased pressure on the food, allowing sharper knives to cut through food more easily
60
describe the effect that the wideness of a tractor tire has on the pressure it exerts on the ground
- the wideness of tractor tires means that, despite its large mass, it exerts a somewhat low amount of pressure onto the ground
- this means that they don't sink into the ground
61
what is the formula for pressure in liquids?
Pressure (p) = density (ρ) × gravitational field strength/acceleration due to gravity (g) x height/depth of fluid column above object (h)
62
why is pressure in liquids (onto an object that provides a force) exerted evenly in all directions?
- liquid particles are close and move freely, so when pressure is applied, they pass the force equally in all directions
- as liquids are incompressible, pressure is distributed evenly throughout the liquid particles
63
why does pressure in a liquid increase with depth?
- as depth increases, there is an increasingly larger volume of liquid above you, adding more weight and greater force per area
- so, higher density = higher pressure at the same depth
64
why does the pressure exerted on an object in a liquid increase with density of liquid?
- denser liquids have more mass in the same volume
- more mass above = more weight = higher pressure at the same depth
