Answer : The correct answer is a) an exothermic reaction that releases energy.
Combustion reaction is generally referred as burning or when hydrocarbon reaction with oxygen to produce carbon dioxide and water . Combustion reaction releases energy. Example :
CH₄ + O₂ → CO₂ + H₂O + Energy or heat .
The reaction which releases energy or heat are known as Exothermic reactions .
Since it says hot dogs and hamburgers are cooked means they are undergoing combustion chemical reaction and so they are exothermic reactions. So option a) an exothermic reaction which releases energy is correct .
Structure 2 is the nucleus.
Friction is helpful:
- We use it to brake for cars
- We use it to fly planes
-We wouldn't be able to turn a door knob without friction ( Our hand would just slide off it)
Friction harmful:
-Our cars would get much better gas mileage without tire and air friction
- There would be no skinned knees if friction didn't exist (Like when your skating or football)
- We could do some pretty cool dance moves without friction
- Our shoes would last longer without friction
Compounds=Chemically combined, fixed proportions,and components change properties.
Both= Made of elements, and 2 or more components.
Mixtures=Physically combined, variable proportions, and components retain properties.
