Temperature Change - Sample Essay
Aim In this investigation, I am going to investigate how increasing the temperature of substance will help determine the Specific Heat Capacity of the substance. Specific Heat Capacity (C) is the energy that is required to raise the temperature of 1kg of a substance by 1 c or 1K. The three variables that affect the specific heat capacity of a substance are: Energy supplied (J) Mass (kg) Temperature change (K) or ( c) The equation that is used to determine the specific heat capacity of any substance is; Specific Heat Capacity = Energy Supplied ( Q) (C) Mass (kg ) Temperature Change ( ).
Unit: Jkg- K- Each different substance have different specific heat capacity, this is because different substances require different amount of energy to change the to increase or decrease the temperature. As all substances have different Internal Energy, this explains why different substances require different amount of energy to change the temperature. Studies from A2 explain that Internal Energy (Thermal Energy) is the sum of the kinetic energy and the potential energy of the molecules in an object or substance. If the temperature of a substance increases so does the internal energy.
Referring back to knowledge gained from A1 when a substance is at a liquid state it has more internal energy than a substance at solid state. This can be explained by the fact that at solid state particles are bonded together so the particles movement is restricted. At liquid state the particles are spaced out s they are able to move randomly so they have more internal energy than particles in a solid, which have their movements restricted. As particles in solids are bonded together this means that heat can be conducted from one particle to another easily.
Conduction transfers thermal energy through the collision of neighbouring particles. Liquids are poor thermal conductors because their particles are not bonded together which makes it had for heat to be transferred from one particle to the other. The way heat is transferred in liquids is through convection. Convection is the heat transfer due to the current movement from warmer particles moving towards the section where cooler particles are and cooler particles moving towards the warmer section of a fluid, this is caused by different densities at different temperature.
This explains why liquids tend to have higher rates of specific heat capacity compared to solids because heat is transferred much quicker through conduction than convection. If you compare the specific heat capacity of copper, (390Jkg- K- ) to the specific heat capacity of water, (4180Jkg- K- ) there is a significant difference. In general the specific heat capacity of a solid is significantly lower compared to most liquids expect from Mercury which has a specific heat capacity of 140Jkg- K- when is in a liquid state. This also explains why H O has a low specific heat capacity when it’s in solid state, ice(21 00Jkg- K- ) compared to when it’s in liquid state, water (4180Jkg- K- ) From my research I found out that there are two laws of Thermodynamics: The first law states that the net heat transfer ( Q) of a systems equal to the sum of the thermal energy.
The second law states that the entropy of an isolated system never decreases. This means that heat cannot be 100% converted to useful energy because the heat released to entropy is never returned to the system. Entropy is like internal energy; it is a thermodynamic quantity that belongs to any system of objects.
It is proportional to temperature. As the temperature increase, entropy increased. In a microscopic level, entropy measures the amount of disorder in a substance. When heat is added to the substance, the particles that make up the substance move faster in a random way. The greater the velocity of the particles this implies more disorder for the substance; therefore increasing its entropy. To voltage. Thus to work out energy we use this equation:
Energy = current voltage time The substance that I will be trying to determine its Specific Heat Capacity is Ethanol. Ethanol, C2H5OH is the second member of the aliphatic alcohol series. Most of the ethanol used is a mixture of 5% water because pure ethanol known as absolute ethanol is too expensive. Ethanol is prepared by a 95% solution, which results from the fermentation of sugars. Ethanol used in industry is made by reaction of ethane and steam. C2H4 + H2O= C2H5OH Ethanol’s has a boiling point of 78. 3 degrees centigrade, which is lower than water’s boiling point. PREDICTION.
I predict that the specific heat capacity of ethanol will be less than that of water, but greater than that of any solid. I’ve come up with this prediction because ethanol has a boiling point which is significantly lower than that of water but it’s still a liquid so it’s specific heat capacity should be between 2000-3000. I suggest this because it’s a liquid and from my research require much more energy to warm up, compared to solids but because it’s more dense than water and it’s particles are closer together than those of water, it would mean that it would require less heat compared to water.
I predict that the results would produce a graph that would show the increase of energy as temperature increases. I predict that line produced by the results should be a straight line and should go through the origin but from my preliminary work I found this wouldn’t happen in the real world because there would be heat loss. Working out the gradient of the graph would produce the specific heat capacity of ethanol. From my preliminary work I learnt that some heat was used up to heat up equipment some was lost through radiation by the beaker, convection we taking place which meant temperature rise was less than should be.
METHOD Equipment RV power pack Joule meter Weighting scale Stop clock Connecting wires Heatproof mat Immersion heat Beaker and Lid Wool Thermometer Ethanol (0. 3kg) The equipment will be set-up as shown in the diagram. As temperature will be variable, that will be controlled so the temperature should rise by at least 10 degrees to be able to plot a graph. I will do three observations to be able to work out an average to plot the graph. From the my preliminary work I learnt that I should use a smaller beaker, less liquid, smaller heater and the beaker should be wrapped by material to reduce heat loss.
The thermometer and joule meter reading should be recorded after every 2 minutes. SAFETY As the experiment involves electricity and liquid, safety precautions will apply. The beaker should be placed on a heat proof mat, don’t touch the power pack or connecting wires with wet hands as this can give electric shock. The heater will be hot so one should be aware, it should be placed on the heatproof mat when removed from the beaker and, Spillages of liquid should be avoid as this makes the floor slippery. FAIR TEST.
To be able to obtain accurate results other variable (mass) should be kept be kept the same through out all experiments. In all 3 experiments the same beaker should be used, same heater, thermometer, joule meter and power pack. All three experiments should be done in the same part of the room to avoid temperature variation. BIBLLIOGRAPHY Title Last Published Useful Information Dictionary Of Physics By Usborne Publishing Ltd 2000 I provided and explanation about Internal Energy Advanced Physics For You By Stanley Thomes Ltd 2000 Lots of information but important about thermodynamics.