Answer: A) grinding coffee beans
Explanation:
A physical change is defined as a change in which there is alteration in shape, size etc. No new substance gets formed in these reactions.
A chemical change is defined as a change in which a change in chemical composition takes place. A new substance is formed in these reactions.
1. Grinding coffee : Only change in size takes place, thus a physical change
2. Baking a cake: the chemical reaction occurs by combination of flour with oxygen , thus a chemical change.
3.:converting water to hydrogen and oxygen: The decomposition iof water takes place, thus is a chemical change
4.Burning of coal: the chemical reaction occurs by combination of carbon with oxygen , thus a chemical change.
<span>They want a full outer shell of electrons, so the lose, gain, or share electrons with other elements, forming compounds, until they have 8 valence electrons and become stable.
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Answer-The correct option is option d with says all of the above.
Explanation- All three acids that are given combined together to form acid rain in which nitric and sulphuric acid are stronger acids present while carbonic acid is a weaker one.
The carbon dioxide admitted in air combines with water to form carbonic acid and gives a weak acidic nature to rainwater. Pollution in nature makes sulphur and nitrogen present in air react to form the stronger acids responsible for acid rain.
Substances that cannot be separated and found on a periodic table are elements.
A
nswer: -
C. Energy is released by the reaction
Explanation:-
An exothermic reaction is one in which during the progress of the reaction heat is evolved.
So energy is released by the reaction.
It cannot be created as energy is neither created nor destroyed as per the Law of conservation of energy. Energy is not transferred either.
The energy released during the progress of the reaction originates from the chemical bonds of the reactants as they break during their conversion into products.
