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MissTica
3 years ago
13

What are the observable indicators that can be evidence a chemical change might have occurred?

Chemistry
1 answer:
kozerog [31]3 years ago
5 0

solution:

The four observations that indicate a chemical change are:  

1) Precipitate is formed  

2) Odour  

3) Heat is emitted ( change in temperature)  

4)Formation of a Gas

Changes of state may of course be merely physical—as for example when liquid water is boiled to form a vapor. (These and other examples of physical changes resulting from temperature changes are discussed in the essays on Properties of Matter; Temperature and Heat.) The vapor produced by boiling water, as noted above, is still water; on the other hand, when liquid water is turned into the elemental gases hydrogen and oxygen, a more profound change has occurred.  

Likewise the addition of liquid potassium chromate (K2CrO4) to a solution of barium nitrate (Ba[NO3]2 forms solid barium chromate (BaCrO4). In the reaction described, a solution is also formed, but the fact remains that the mixture of two solids has resulted in the formation of a solid in a different solution. Again, this is a far more complex phenomenon than the mere freezing of water to form ice: here the fundamental properties of the materials involved have changed.  

The physical change of water to ice or steam, of course, involves changes in temperature; likewise, chemical changes are often accompanied by changes in temperature, the crucial difference being that these changes are the result of alterations in the chemical properties of the substances involved. Such is the case, for instance, when wood burns in the presence of oxygen: once wood is turned to ash, it has become an entirely different mixture than it was before. Obviously, the ashes cannot be simply frozen to turn them back into wood again. This is an example of an irreversible chemical reaction.  

Chemical reactions may also involve changes in color. In specific proportions and under the right conditions, carbon—which is black—can be combined with colorless hydrogen and oxygen to produce white sugar. This suggests another kind of change: a change in taste. (Of course, not every product of a chemical reaction should be tasted—some of the compounds produced may be toxic, or at the very least, extremely unpleasant to the taste buds.) Smell, too, can change. Sulfur is odorless in its elemental form, but when combined with hydrogen to form hydrogen sulfide (H2S), it becomes an evil-smelling, highly toxic gas.  


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sertanlavr [38]
In the periodic table, elements of the same group are characterized by having the same similar properties.
So, first we will check the elements that lie within the same group as <span>beryllium  and then we will attempt to choose the elements with atomic mass higher than 130.

So, elements in the same group as </span>beryllium are: magnesium, calcium, strontium, barium and radium.
Among these elements, we will find that:
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Based on this, the two elements would be barium and radium.

3 0
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The process of adding hydrogen to the double bonds in unsaturated fatty acids to extend the shelf-life of food products is calle
Viktor [21]

Hydrogenation is a process that involves adding hydrogen to the double bonds in unsaturated fatty acids to extend the shelf-life of food products.

<h3>What is hydrogenation?</h3>

Hydrogenation can be defined as a chemical process that involves an addition of hydrogen to the double bonds in unsaturated fatty acids to extend the shelf-life of food products.

<h3>The purpose of hydrogenation.</h3>

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Read more on unsaturated fatty acids here: brainly.com/question/1580524

8 0
2 years ago
2H2 + O2 → 2H2O
pantera1 [17]
Okay
Mr (H2O)= 18g
therefore moles of H2O
is 720.8/18= 40.04mol
the ratio of H2 to O2 to H2O is
2 : 1 : 2
so moles of H2 is same as H2O here
H2= 40.04moles

moles of O2 is half
so 40.04 x 0.5
20.02moles

grams of O2 is
its moles into Mr of O2
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Answer:

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Explanation:

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