Energy
List the stores of energy (100 per)
Gravitational Potential
Elastic Potential
Kinetic
Chemical
Thermal
Magnetic
Electrostatic
Nuclear
Draw a heating curve from solid to gas. Label the state changes
See small whiteboard
After 300 years, the activity of a Uranium sample fell from 15,000Bq to ~470Bq.
What is the approximate half life of this sample?
Worth 400 points...
0 - 15,000, 1 - 7500, 2 - 3750, 3 - 1875, 4 - 937.5, 5 - 468.75
5 half lives
300/5 = 6 years
What is meant by the resolution of a piece of equipment?
The smallest measurement on the piece of equipment.
A car travels 20m/s on a road. It has a mass of 1240kg. What is the kinetic energy of the car?
Ek = 0.5 x m x v2
Ek = 0.5 x 1240 x 202
Ek = 248,000 J
What does specific latent heat tell us?
What are the two types?
The energy required to change the state of 1kg of a substance.
Vaporisation - liquid-gas or gas-liquid
Fusion - solid-liquid or liquid-solid
Describe the motion of particles in a gas
Random directions
Random speeds
A radioactive rock is being tested to see what radiation it emits.
It does emit alpha radiation, how could you test to see if it emits other radiation?
If the count rate drops to background when paper is placed near the emitter then only alpha is emitted.
If the count rate drops to background when an aluminium sheet is used instead, it emits beta radiation.
Otherwise it emits gamma radiation
Why are repeat measurements useful?
Minimum two reasons
Minimise affect of random errors
Allows us to take a mean
Can remove anomalous values.
A hairdryer has a power of 2300W, how long would it take to use 15,000J of energy?
E = Pt
15000 = 2300 x t
15000 / 2300 = t
t = 6.52....s
Jeffrey Archibold III wants to replace the energy source in Mr Holmes' imagination land. He says that just using wind and solar will provide enough energy on average. So it will work.
Why did Mr Holmes challenge him to a fortnite 1v1 over his claim?
Solar and wind are both unreliable stores of energy. This means that they cannot produce energy at all times, even if the average energy per day is enough.
This will mean that unless there is good energy storage, a power surge or need for energy will result in Mr Holmes imagination land being without energy.
Also Mr Holmes is cracked at fortnite.
If you triple the volume of a container of gas, what will happen to the pressure on the surface of container?
What assumption have you made?
At a constant temperature
pressure is inversely proportional to pressuer
therefore it will be divided by 3
Write the beta decay of V-52 into Cr. Vanadium has an atomic number of 23.
V → Cr + β
Show the values of the main SI prefixes. (e.g., nano)
T - x1012
G - x109
M - x106
k - x103
-
m x10-3
µ - x10-6
n - x10-9
p - x10-12
cast iron - 1kJ/kg
pig iron - 500,000mJ/kg
wrought iron - 950 J/kg
pure iron - 1200J/kg
1.5MJ = 1,500,000J (1.5 x 106)
1,500,000 = 1400 x L
1,500,000/1400 = L
L =1071.4... J/kg
Closest value is cast iron (1000J/kg).
Mr Holmes (highest mass), a golden retriever (lightest mass) and Mr Baxter (Middle mass) all start at the same height on 3 identical slides.
Assuming a closed system, who will reach the bottom first, why?
Double point bonus: What would be different in an open system.
If all Ep = Ek, then mass on both sides will cancel
v2 = 2gh
This means that mass will not affect their velocity down the slide.
In an open system work will be done against air resistance and friction, dissipating energy as heat to the surroundings.
What is meant by internal energy?
Internal energy is the total kinetic energy and potential energy of all of the particles in a system.
Two pure water samples are taken from the same
river.
Explain how irradiating sample A and contaminating sample B will affect the hazard caused by drinking the water.
Irradiating
water exposed to radiation
(which) does not affect the hazard
OR
because radiation can kill pathogens (1)
(irradiating) decreases the hazard (1)
contaminating
because radioactive isotopes will enter the water / body
(contaminating) increases the hazard
A company claims to have achieved 100% efficient energy transfer in a public post.
What would scientists need to do to verify this, why?
Peer review helps to detect false claims and to establish a consensus about which claims should be regarded as valid.
Without it the publishing may be oversimplified, inaccurate or biased.
A 50m bungee cord has a spring constant of 1.5kN/m, when Mr Holmes jumps, it gains 800,000J of elastic potential energy.
What is the length of the extended cord?
1.5kN/m = 1500N/m
Ee = 0.5 x k x e2
800,000 = 0.5 x 1500 x e2
SQRT(800,000/750) = e
e = 32.7m
Final length = 50 + 32.7 = 82.7m
Draw a cooling curve from boiling water to room temperature, add two lines
- well insulated
- badly insulated
What are some variables that would need to be controlled to do this with more materials? (minimum 2)
See small whiteboard
Initial temperature of water
Volume of water
Container
Thickness of insulation
A.O.A
A balloon full of helium is heated.
The mass and volume of helium in the balloon remain constant.
Explain why the pressure exerted by the helium inside the balloon would increase.
Perfect answer = 1000 points. Otherwise = 0
-particles would have a higher (mean) kinetic energy
-increased number of collisions with the walls of the balloon per second
-greater forces exerted in collisions (between particles and balloon walls)
-greater force exerted on same area = greater pressure
Summarise the work of the main scientists in the development of the modern atomic structure.
MUST INCLUDE ALL SCIENTISTS.
Dont Try Remember Boring Chemists
Dalton - solid spheres for different materials
Thomson - plum pudding, electrons in positive sphere
Rutherford - Nuclear model, small positive nucleus
Bohr - As above but with electrons orbiting at set distances (energy levels)
Chadwick - discovered neutrons
A coffee machine heats water from 20oC to 90oC.
The power output of the coffee machine is 2530W.
The specific heat capacity of water is 4.2kJ/kgoC
Calculate the mass of water that the coffee machine can heat in 14 seconds.
4.2kJ/kgoC = 4200J/kgoC
90-20 = 70oC
E = Pt
E = 2530 x 14
E = 35420J
E = mcΔθ
35420 = m x 4200 x 70
35420 / 294000 = m
m = 0.12kg