5 Solids Liquids Gases- Part C “Change of State” Triple Only
Syllabus Aims…
5.8P explain why heating a system will change the energy stored within the system and raise its temperature or produce changes of state
5.9P describe the changes that occur when a solid melts to form a liquid, and when a liquid evaporates or boils to form a gas
5.10P describe the arrangement and motion of particles in solids, liquids and gases
5.11P practical: obtain a temperature-time graph to show the constant temperature during changes of state.
5.12P know that specific heat capacity is the energy required to change the
temperature of an object by one degree Celsius per kilogram of mass (J/kg °C)
5.13P use the equation:
change in thermal energy = mass × specific heat capacity × change in temperature
ΔQ = m × c × ΔT
5.14P practical: investigate the specific heat capacity of materials including water and some solids and obtain a temperature time graph to show the constant temperature during a change of state.
Change of State | Matter | Physics | FuseSchool On Earth, materials exist [...]
Change of State | Matter | Physics | FuseSchool
On Earth, materials exist in one of three main states of matter: solid, liquid or gas.
Materials can change between these states. ... When a state change occurs, a substance’s properties will also change. However, if the state change is reversed the substance will recover the properties it had to begin with. Matter can transition between the three states when heated or cooled. But why is heat key in all this? When a material is heated, it absorbs heat energy. This additional energy can cause attractive forces between molecules to break. This leads to rearrangements of the particles because the attractive forces no longer hold them together as tightly. The same happens when a liquid is heated. The attractive forces between the molecules break, leading them to become more widely dispersed and a gas to form.
Do you know the difference between evaporation and boiling? Both are when a substance transforms from a liquid to a gas. Think of a boiling pan of water… all of the water bubbles. This is because all of the particles have enough energy to become gaseous. But water standing in a pan that is not being heated by anything other than the environment, can also turn into a gas - this is evaporation. Only the particles at the surface have enough energy to change from liquid to gas. Hence, evaporation is a slower process than boiling even though it achieves the same state change. Both are types of vaporisation.
The opposite of these vaporisation processes is condensation: the transition from gas to liquid. Think of a cold can of soda on a hot day - those water droplets on the outside. Or the dew on the grass in the morning. Or the steamed-up mirror after a hot bath. Even the clouds in the sky. Or a foggy windscreen on a car. These are all examples of condensation. Water vapour in the air has cooled down to form liquid droplets of water.
Now let’s think about the transitions between solids and liquids: so, melting and freezing. Think of the Arctic sea ice. In the summer when air temperatures are warmer, more heat energy is absorbed by the ice. This causes bonds to break between the ice’s water molecules and the ice starts to melt. The solid ice becomes liquid water. But in the winter, the air temperatures are colder and so seawater freezes and the ice starts to form again. There is less heat energy within the ice, and so more bonds can form, holding it together as solid ice . Did you know that sometimes when solids are heated they can turn straight into gases? This is called sublimation. This is only demonstrated by particular materials such as solid carbon dioxide (AKA ‘dry ice’). When subjected to a certain pressure it will turn straight into gaseous carbon dioxide. Liquid carbon dioxide does exist but it only occurs under very high pressures. Similarly, gases can turn straight into solids when cooled. This is called deposition.
Our final thing to discover is that when a material changes states the mass stays the same. The density changes - so the mass per unit volume. But the mass does not change. Our glass of nice, cold coke weighs the same whether the ice is solid or when the ice has melted.
So, there we have the changes of state. Just remember that the mass stays the same, whatever the state!
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Specific Heat Capacity - GCSE Science Required Practical
Mr Rees shows you how to measure the SHC of a material using the graph [...]
Mr Rees shows you how to measure the SHC of a material using the graph method. ------------------------------------------ 00:00 Experiment setup 01:08 SHC equation 02:57 Calculating power from V & I 04:50 Analysing data
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Specific Heat Capacity of a Metal Block - GCSE Physics Required Practical
Follow these steps to carry out the core practical finding the specific [...]
Follow these steps to carry out the core practical finding the specific heat capacity of metals. 1. Connect a power supply to a joule-meter that is connected to an immersion ...heater. 2. Insert the immersion heater and a thermometer into the metal block. 3. Insulate the metal block with cotton wool. 4. Record the temperature reading from the thermometer. 5. Turn the power supply on for 5-10 minutes, so that the immersion heater begins heating up the metal block. 6. When the change in temperature is 10 degrees, turn off the power supply and note down the reading on the joule-meter. 7. Use the specific heat capacity equation make your calculation!
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