Ch - 10 (Thermal Properties of Matter) Flashcards
What happens when thermal expansion takes place?
- Temp increases
- Volume increases
- molecules move faster
- molecules move farther
Which state of matter expands the most?
Gas > Liquid > Solid
If an object tht is small and big expanded, which one would expand faster and why?
The one that is bigger because it has more particles.
What is an example of expansion in real life?
- The railway tracks.
- When there is a gap there is no buckling.
What is an example of contraction in real life?
- Power towers with pylons.
- They are not straight tied so they do not contract.
What happens when a material expands?
- Particles don’t get bigger
- They move around more and take up more space.
Define specific heat capacity.
Energy needed to raise temperature of 1kg of the substance by 1°C.
What is the formula for thermal energy?
Mass (kg) x speciofc heat capacity (Jkg°C) x Temp change
E = mv delta T
What is the formula for energy transferred?
Mass (kg) x specific latent heat (Jkg)
E = ml
Define latent heat.
- Energy transferred in a process without the change of the body’s temperature.
Or
- Heat or energy that is absorbed or released during a phase of a substance.
What is internal energy made up of?
KE
Chemical PE
What happens of we supply thermal energy to an object?
Gain KE
What is the specific heat capacity of water?
4200 J/kg°C
What is the specific heat capacity of aluminium?
910 J/kg°C
What is the specific heat capacity of polythene?
2300 J/kg°C
What is the specific heat capacity of steel?
420 J/kg°C
What is the specific heat capacity on land and water? And what warms up quickly?
Land: lower SHC = heats up faster
Water: Higher SHC = heats up slower
Land
Which state/s does thermal expansion happen in?
Solids, liquids, gases
What are the applications of thermal expansion?
- Thermometers (liquid expands with temp)
- Switches (bimetallic strip bends upwards)
What are the consequences of thermal expansion?
- Solids: Buckle if too hot.
- Ex: Metal railway tracks, Road surfaces, bridges
Define internal energy.
The total energy stored inside a system by the particles that make up the system due to their motions and positions.
What affects the kinetic energy?
Motion of the particles
What affects the potential energy?
position of the particles relative to each other
What can the increase in KE (IE) do?
- Temp increases
- Change of state
What factors affect how much the temp of a system increases?
- Mass
- Type of material
- Amount of thermal energy into system
Define fixed points.
The melting and boiling points of pure water are known as fixed points.
What temp does ice melts?
0°C
What temp does pure water boil at?
100°C
What happens when a substance is changing state?
- melting or freezing
- boiling or condensing
The substance does not change temperature
What happens during boiling?
- Thermal energy supplied
- at b.p., temp does not increase (internal energy does not rise)
- additional thermal energy overcomes intermolecular forces
- liquid evaporates
What is another name for evaporation?
Vaporisation
How is the process reversed?
Cooling energy is transferred away
- A gas turns into a liquid (condensation)
What happens during melting?
- ice is heated using thermal energy
- at m.p. Temp does not change (internal energy not rising)
- additional thermal energy overcomes intermolecular forces in solid.
- solid turns to liquid from melting
- heat transferred away and it freezes
Define heating.
Energy is transferred to the system and the KE of molecules increases (arrow to right)
Define cooling.
Energy is transferred away from the system (dissipates to surroundings)
Define the procces of condensation.
- Lose KE and move slowly
- no enough energy to overcome intermolecular forces
- particles get close together
- particles flow over each other
- gas condenses to liquid (no change of themp)
Define the process of solidification.
- particles lose KE and move slowly
- don’t have energy to overcome intermolecular forces
- particles get close togetehr
- vibrate in fixed position n it turns from liquid to solid.
What does a heating/cooling curve if a substance show?
Energy changes the temp is increased/decreased
Define evaporation.
Change in state of a liquid to gas
When does evaporation happen?
- at any temp
- only from surface of liquid
How is the energy in a liquid?
- molecules have range of energy
- average energy relates to temp of liquid
When does evaporation occur?
- more energetic molecules move near to the surface of the liquid. Particles evaporate
- average energy of liquid is reduced
- liquid is cooled down by evaporation
What affects the rate of evaporation?
Temperature, SA, air movements
What happens when temp is increased for evaporation?
- KE of molecules increases
- molecules overcome intermolecular forces (holds in liquid to escape from sueface)
- High temp –> High SA
What happens when SA increases for evaporation?
Molecules only escape the intermolecular forces of attraction at the surface of the liquid.
How does air movement affect evaporation?
- dries air and allows more water movement
What happens in evaporation and cooling?
- An object in contact with an evaporating liquid, both solid and liquid cools.
- refrigerator and air conditioner
Define boiling.
Change in state from liquid to gas.
When does boiling happen?
- happens only at b.p.
- happens all through the liquid
