heating and cooling
heating and cooling - what is temperature.
temperature is the measure of how hot or cold something is. we can measure temperature in degrees Celsius and we use a thermometer to measure temperature. to make something hotter we have to give it energy. this energy is called 'thermal energy' or 'heat energy' all substances are made up of particles ( atoms, ions and molecules)
we heated a pin and then stuck it into ice here are our conclusions
when we heated the pin the particles started vibrating meaning the particles got looser meaning it was getting hotter. when we then stuck the pin into the ice it made a sizzling noise because the heat from the pin melted some of the ice. this is because the particles in the ice are tightly packed together but when the hot pin was on the ice the particles vibrated lots and started to get looser leading to the ice melting.
experiment 2 - we heated up a jug of water and put ina ice cube. when we heated up the water it got quite hot so this means when we put the icecube in it meant that the ice cube melt because the particles in the ice cube were vibrating and spreading out more turning it into a liquid.
experiment 1+2 on heating
the difference between heat and temperature is that heat is energy and temperature is how hot or cold something is. you measure heat in joules and you measure temperature in degrees celcius.
experiment 1 - heating a ball that before heated fit through a hole - before we heated the ball it easily went through the hole but when we had heated it for two miniuts it couldnt fit through the hole. this is because as the ball was being heated the particles got looser and moved around more. they were vibrating and the heat was transfering over to the ball. when the ball gets heated up it expands but when it starts to cool down it contracts.
everything is made of small particles in a solid these particles are held together quite tightley. the particles can move by wobling or vibrating in their fixed position like bottels in a crate. heat energy makes the particles wobble more. we feel this increase in vibration as the object getting hotter.
experiment 2-heating a strip made of two thin strips of metal - the brass is made of two thin strips of metal. when it i heated the particles vibrate more and this makes the metal expand. this then bends because the distance around the outside of the curve is greater then round the inside. if it was then cooled instead of heated it would bend in the opposite way.
expansion of gas.
experiment 1 putting a long tube with air at the top in to a glass of water with our hands around.
when we put the water we put our hands round the glass which means the air inside the glass vibrated more and needed more space so the air needed to go somewere but the only place it could go was down the tube into the water which created bubbles. when we took our hands of the glass it cools and it contracts and the water has to take up the space of the air particles.
energy heat transfer
which would feel warmer if we picked up a piece of wood or copper which were both at room temperature.
the wood would feel warmer because it is a poor conductore. so it would not conduct heat away from your hand as quickley as the copper.
what happens if we heat part of a metal rod.
the particle in that part of the rod vibrate.
the particles pass on the vibration to other particlesin the rod.
think about the vibrating particles again.... when they vibrate they take up more space. the object they are part of expands.
this happenes in solids,liquids and gases.
in liquids and gases the heated part is less dense.
so it floats up through the cooler liquid or gas above it.
this is called cpnvection.
the heat in a hot air balloon is pushed up meaning it pushes the balloon uo.
another example if convection is a chinese latern and another example is a lava lamp.
so convection is when heat is transferred from on part of the room to all parts of a room by for example a heater.
there is a radiator (on) in the bottom corner of a room. the heat rises and as it is going up it pushes the other heat to the side as the heat cools it goes back down this circular movement is called the convection current.
conduction is when heat is transferred from on particle to anoother to another to another the only thing that can stop conduction is an insulator. a conductor doesnt stop donduction.
insulator - something that stops hear from passing through eg... wool, wood,plastic and other non metals.
coductor- something that lets heat through. it is the opposite to insulator. exampels .......... magnesium, copper aluminium and other metals.
radiation is when heat energy is transferred.
in hot contrys it is better to have a white house beacuse white reflects radiation but black absorbs radiation.