Their principal function is to help the fish swim. Fins located in different places on the fish serve different purposes such as moving forward, turning, keeping an upright position or stopping. Most fish use fins when swimming, flying fish use pectoral fins for gliding, and frogfish use them for crawling.
Answer: THE MIDDLE OF THE EARTH IS KNOWN AS THE CORE.
Explanation: The core can be defined as the middle of the earth. It is composed mostly of iron, some nickel, and about 10- 15 percent of a less dense material, probably silicon, oxygen, or sulfur.
The temperature at the inner core's surface is estimated to be approximately 5700 K (5430 °C or 9806 °F), which is about the temperature at the surface of the Sun.
Answer:
B.
C.
Explanation:
Factors control the cooling time of magma within the crust include surface water passing over the magma and the depth at which the magma cool.
Surface water passing over the magma absorbs the water and carries away heat and magma present in depths is cooler than surface because magma rises to earth surface due to high pressure and that is hot.
Hence, the correct option is "B. and C."
Fossil fuels store their energy in the chemical bonds that hold the hydrocarbon molecules together. That energy can stay trapped like that right up until the moment the hydrocarbons meet both heat and oxygen (O2).
Heat (from a match or spark) breaks the hydrocarbon and oxygen molecules apart, and then oxygen atoms react with the freed carbon and hydrogen atoms to give carbon dioxide (CO2) and water (H2O), and loads of energy as heat along the way.
combustion - burning fuel for energy
That extra heat is the key to fossil fuel's success. More heat energy is released when the new bonds form in CO2 and H2O than it took to break the original bonds in oxygen and the fuel. So once combustion starts, it's a runaway chain reaction giving off excess heat.
We've used the heat directly for cooking and warming, and indirectly to boil water for steam-powered turbines for electricity. The gases given off from burning fuels have driven pistons in internal combustion engines for more than a century.
Not only can we start a fire with a single spark, we can stop it by cutting the supply of fuel, air or heat, so it's a source of energy we can turn on and off as needed.
A controllable source of energy that has only two major downsides — finite supply and being the source of the CO2 that's driving climate change. No wonder fossil fuels have been such a hard habit for industrialised countries to kick.
