Thermal Physics 5.1 Flashcards
What is temperature?
-A measure of how hot or cold an object is. It is a measure of the kinetic energy of an objects total internal energy.
What is the absolute scale of temperature?
-A scale of temperature which isn’t dependant on any physical properties and starts at absolute zero
What is absolute zero and the triple point of water?
-The temperature at which particles of matter have minimum internal energy
-The value of absolute zero(0 kelvin) is -273.16 degrees Celsius
-The triple point of water is the point at which solid, liquid and gas particles of water exist simultaneously which is 273.16K
What is thermal equilibrium?
-The point at which objects in contact with each other are at the same temperature, so no net heat flow
A small block of aluminium with an initial temperature of 75 degrees celcius is placed in a bath tub full of water at 15 degrees Celsius suggest the temperature of thermal equilibrium and why?
-Around 20-25 degrees Celsius
-The water is very large in comparison to the aluminium block so the aluminium block has small thermal energy store therefore it can only transfer a small amount of energy to the water and the temperature of the water won’t increase by much
Describe using the kinetic model of matter how the particles are in solids?
-Close together due to their strong forces of attraction and vibrate about their individual fixed positions
-Generally have a high density and definite shape
Describe using the kinetic model of matter how the particles are in liquids?
-Particles slide past each other, separation is greater than in solids and attractive forces are weaker.
-Lower densities than solids but can flow and be poured
Describe using the kinetic model of matter how the particles are in gases?
-Particles are free to move, in random directions
-Forces of attraction are weak and their is high separation between particles
-They generally have low densities and can be compressed easily
What is internal energy?
-Internal energy is defined as the sum of all the kinetic and potential energies within a system
What factors affect internal energy?
-Temperature: a higher temperature means that the particles have a higher kinetic energy
-States of matter: gases have the highest internal energy and solids have the lowest
-Intermolecular forces: higher intermolecular forces means more potential energy
How can you increase the internal energy of a system?
-Do work to the system by heating it up
Why does steam at 100 degrees have more internal energy than water at 100 degrees?
-Steam particles have more kinetic energy than water particles
-Energy has to be supplied to the particles of steam to overcome the forces of attraction.
What is Brownian motion?
-The random movement of small visible particles in a fluid due to collisions with much smaller, randomly moving atoms
What are the different patterns of movement in solids, liquids and gases when heated?
-For solids the particles will vibrate more and still be held in their equilibrium positions.
-For liquids some heat will be transferred into translational kinetic energy and the molecules move past each other faster
-For gases, All heat is transferred into translational kinetic energy and particles will collide faster
What is specific heat capacity?
-The amount of energy needed to raise the temperature of 1kg of the substance by 1K
What is the equation for specific heat capacity and its units?
How do you determine the value of specific heat capacity of a material?
- Insulate material so that as much thermal energy is being supplied
- Add an ammeter and voltmeter to the circuit and obtain values as current is flowing, find power P=IV
- Obtain a value for energy transferred E=P*Δt
- Use E=mcΔθ and the values of the thermometer to get a value for specific heat capacity of material.
Define specific latent heat of fusion and specific latent heat of vaporisation?
-fusion: the amount of energy required to change the phase of 1kg of substance from solid to a liquid
-Vaporisation: the amount of energy required to change the phase of 1kg of substance from liquid to gas
What is an equation that can be used to work out the energy needed to change a phase of mass?
Describe an investigation to determine the specific latent heat of vaporisation?
- Measure the amount of vapour thats passes through the condenser over the same time at 2 different powers of heater
- Use the equation (V₂I₂ - V₁I₁)t=(m₂-m₁)Lᵥ to get the specific heat of vaporisation
Describe an investigation to determine the specific latent heat of fusion of water?
- Set up apparatus as shown, place a known mass of ice in A and B, attach a voltmeter and ammeter to A to find the power of heater A (P=IV)
- Switch on heater A and after 15mins switch off the heater and measure the mass of water in beaker A and B. The difference in mass is the amount of water that has been melted due to electrical input
- Use L🇫=E/ΔM to find specific latent heat of fusion
Why does internal energy change during a phase change but temperature does not?
-The temperature remains constant as there is no change in kinetic energy
-However the internal energy does change as there is a change in potential energy as the forces between the molecules are changing
Draw a graph to show the change in temperature while ice changes phases to steam?
What is a mole?
-One mole of any substance is the amount of substance that will contain an Avogadro’s constant number of particles
-This amount is its relative atomic mass in grams for example 12g of carbon 12 contain one mole of substance
