internal energy and energy transfers

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mims 😻

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Specific heat capacity is the amount of heat energy required to raise the temperature of a substance by a certain amount.
energy is stored inside a system that is made up of particles - this is called internal energy
internal energy is the total kinetic and potential energy of all the particles in a system, measured in joules
we can use models of several balls and springs to help understand the nature of internal energy, the balls represent molecules and the springs represent the bonds between them (that keep the atoms together)
heating changes the energy stored within a system by increasing the kinetic energy of the particles
heating can increase the temperature of a system, but it can also change the composition of the system (changing state - eg/ liquid to gas)
usually, when a solid melts, there is a small increase in volume - the atoms increase their separation and there is an increase in the potential energy stored (leading to an increase in the internal energy)
specific heat capacity is defined as the amount of energy required to raise the temperature of 1kg of a substance by 1 degree celsius
the amount of energy needed to raise the temperature of a substance depends on its mass and the specific heat capacity of the material
when we say that water has a high specific heat capacity compared with other substances, this means that more energy is needed to raise its temperature than most other materials
water's high specific heat capacity makes it useful for cooling down hot objects without being affected itself
when we add energy to a sample of matter, some of this will be used to overcome intermolecular forces and so increase the average kinetic energy of the particles
if all the added energy goes into raising the temperature of the sample, then the specific heat capacity is equal to the ratio of the energy transferred divided by the product of the mass and the temperature rise
in general, solids have higher specific heat capacities than liquids which have higher specific heat capacities than gases
a large quantity of energy is needed to melt ice because the bonds between molecules are strong
melting occurs when a solid turns to liquid. the internal energy of the system increases
freezing occurs when a solid is cooled below its freezing point. the internal energy of the solid decreases and the particles move faster.
boiling or evaporation occurs when a liquid turns into a gas and the internal energy increases.
condensation occurs when a gas turns into a liquid - the internal energy of the system decreases.
sublimation occurs when a solid turns directly into a gas - the internal energy of the system increases,
sublimation is rare
a change of state is a physical change. it does not produce a new substance and the process can be reversed.
heat added or extracted will not change the temperature if two phases are present (eg/ adding temperature whilst freezing does nothing).
when the temperature of a system is increased by supplying energy to it, the increase in temperature depends on:
the mass of the substance heated
what the substance is made of
the energy put into the system
the specific heat capacity of water is 4200 joules per kilogram per degree Celcius (J/kg°C).
energy = m x c x ΔT 
(energy = mass x specific heat capacity x temperature change)
the specific heat capacity of a substance is the amount of energy needed to raise the temperature of 1kg of the substance by 1 degree
water's specific heat capacity = 4200 J/kg°C
alcohol's specific heat capacity = 2400 J/kg°C
glass' specific heat capacity = 630 J/kg°C
dry air's specific heat capacity = 1000 J/kg°C
water has a very high specific heat capacity of water, this means that 1kg of water requires a lot of energy to heat it up and a lot of energy mus be transferred to cool it down
since we are made mostly of water, our body temperature does not increase too much when we exercise or cool too quickly when we go outside in the cold
c = e/mΔT 
heat capacity = energy/mass x temperature difference