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Heat
Junior Cert
Question | Answer |
---|---|
Heat | Heat is a form of energy. |
Heat Units | It is measured in Joules. |
Heat Travel from..? | Heat moves from hot areas to colder areas. |
Conduction | Conduction is the transfer of heat through a solid from particle to particle. Heat moves but particles don't. |
Convection | Convection is the transfer of heat through a liquid or gas. Molecules of the liquid or gas move upwards and carry the heat. |
Radiation | Radiation is the transfer of heat by rays without needing a medium to pass through. |
Insulator | Poor conductors. |
Conduction Experiment | Different Solid metal and non-metal Bars (horizontal - one end in boiling water), Pin and wax. |
Convection Experiment | Potassium Permanganate Crystals in water in a beaker. Lighted Candle under crystal. |
Expansion and Contraction | Solids, liquids and gases all expand when heated and contract when cooled |
Bimetallic Strip | A bimetallic strip consists of two metals (e.g.Copper and Iron) fused together which expand a different amount when heated. This causes the strip to bend when heated. They are used in thermostats, e.g. the thermostat in a smoke alarm. |
Water's Strange Property | Water is at its most dense at 4 degrees Celsius. When cooled below or heated above 4 degrees, it begins to expand. |
Experiment: Expansion Contraction of Solids | Ball and Ring. Ball expands when heated (doesn't fit through ring) and contracts when cooled.(passes through ring) |
Experiment: Expansion Contraction of Liquids | Round bottomed Flask with straw completely full. Level rises when heated. |
Experiment: Expansion Contraction of gases | Empty Round bottomed flask with straw. Straw placed in water. Bubbles with expansion. Water sucked up straw when cooled. |
Temperature | Temperature is a measurement of heat. |
Units of Temperature | Temperature is measured using a thermometer. It is measured in degrees Celsius. |
Freezing and Boiling points of Water. | Water freezes at 0 degrees Celsius and boils at 100 degrees Celsius. |
Amount of Heat Energy. | The amount of heat in a substance depends on the substance, its temperature and it’s mass. |
Latent Heat. | Heat that cause a change in state but not a change in temperature e.g. when ice melts with no rise in temperature. |
Effect of Increased Air Pressure on the Boiling Point of Water | Raises the Boiling Point above 100 degrees Celcius |
Effect of lowering the Air Pressure on the Boiling Point of Water | Decreases the Boiling Point above 100 degrees Celcius |
Effect of Dark Coloured Cans on heat transfer by radiation | Lose heat rapidly |
Effect of Light (silver) Coloured Cans on heat transfer by radiation | Lose heat slowly |
Poor Conductors | Polystyrene, Dry Air, Water, All are good insulators |
Poor Insulators | Metals. All are good conductors |
Heat travels in 3 ways | Conduction, Convection & Radiation |
To Investigate Conduction and Convection in Water Experiment | Test tube with water, ice and a coin to weigh it down. Boil the water at the mouth of the tube with a bunsen burner while ice stays at bottom |
To Show Transfer of Heat by Radiation | Two cans - one shiny outer surface & one dull black outer surface both filled with boiling water. Thermometers in each show a drop in temp with the black can losing heat faster. |
Cooling Curve | A graph showing how temperature changes over time as a substance cools. |
Latent Heat of Fusion | When heat changes a solid to a liquid with NO temperature change |
Latent Heat of Vapourisation | When heat changes a liquid into a gas with NO change in temperature |
How to show Water expands when cooled below 4 degrees celsius | Place a glass bottle (with a tightly fitting lid) filled to the top with water in a freezer overnight. It shatters due to the water expanding as it turns to ice |