Heat and temperature Flashcards
What is heat
Heat is the total amount of thermal energy in an object
What is temperature
The average amount of energy in an object or how hot or cold an object is
What is the law of conservation of energy
Energy cannot be created or destroyed, only changed or transferred
Thermal energy always moves from _________ to ___________ places
hotter to colder
How is thermal energy transferred in solids
Conduction
How is thermal energy transferred in liquids
Convection
How is thermal energy transferred in gases
Radiation
Explain how conduction happens
In solids, particles vibrate in fixed position when heated. Conduction occurs when a solid is heated allowing the bottom particles to vibrate. The particles then transfer these vibrations to the other particles
Why are pans made of metal when cooking.
This is because metals are good conductors meaning they allow heat to pass through them. In this case, it allows the food to cook quicker because the heat is being applied to it.
Why are clothes for cold weather made from insulating materials.
This is because insulators don’t allow heat to pass through them.
Explain how convection happens
Convection occurs when heat is transferred through the movement of liquids/gases. As the fluid heats up, it becomes less dense and rises. Cooler, denser fluid sinks to take its place, creating a pattern knwon as the convection current. This cycle continues, transferring heat through the fluid.
Why does convection happens in liquids and gases but not solids
This is because liquids and solids can move but solids stay in a fixed position
What is radiation
Radiation is the transfer of heat through electromagnetic waves without needing a medium
What are some features of the best emmiters and absorbers of radiation
- They are dull
- They are black
- They have a large surface area
What are some features of bad emmiters and absorbers of radiation and good reflecters of radiation
- They are shiny
- They are white or silver
- They have a small surface area
How does cooling down happen through evaporation
Evaporation happens when heat is applied and liquids change to gas. In this process, the highest energy particles escape the liquid and turn to gas, reducing the thermal energy.
Explain how our body loses heat through sweat even though the sweat is the same temperature as the body
When we are too hot, our body produces sweat and transfers thermal energy from the body to the sweat. When the sweat evaporates, the highest energy particles leave, cooling our bodies.
Why does perfume feel colder than water
Perfume has weaker forces than water, meaning it evaporates quicker. This also means that it removes thermal energy quicker than water, producing a cool feel
What are shiny, white or silver surfaces good at
Reflecting radiation away
What happens to the speed in transfer of thermal energy when there’s a large temperature difference compared to small one
The large temperature difference causes faster thermal energy transfer
Why does a spark from a sparkler not cause burns
The spark has a much lower particle size than the sparkler. As a result , it has also has a lower temperature. The spark has a big temperature difference between its temperature and the air so it loses its heat quickly
When thermal energy moves from a hot object to a cold object, we say it has __________________
dissipated
What are radiators meant to do
To cool
State the law of energy conservation
Energy cannot be created or destroyed only changed or transferred
What happens to the mass or energy of a material before and after doing something
It stays the same because of the law of energy conservation
