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new substances are formed with new properties.
when a object changes its form
A chemical reaction has occurred when the chemical identity of a the reactants is different from that of the products. The evidence for this could be obvious or very subtle. For instance, if a colorless gas reacts to form another colorless gas, there would be no visible sign of the reaction. However, often a chemical reaction will cause a change in color or the formation of a solid. The tools you might use to determine if a reaction has taken place depends a great deal on what the suspected reaction is (or what the products formed would be). The most common method is to use analytical chemical technique to verify the presence of the product molecules, or the disappearance of reactant molecules.
Note that there are many physical changes that can be confused with chemical changes. For instance, boiling water or freezing water results in many changes in the properties of water, but those are physical changes, not chemical ones. But whether water is liquid, solid or a gas, it is still water, and that is why it is a physical rather than chemical change.
See the Related Questions for more information about the difference between chemical and physical changes.
(Emperor-A) Here are some evidence they are-
A colour change
A gas given off
A temperature change
there are 7 ways to spot if a chemical reactions is occurring:
1. A Temperature change
2. A color change.
3. A precipitate is formed (an insoluble substance)
4. A gas is given off.
5. Light may be given off
6. Odor may be given off
7. Sound may be given off
Basically if there are any permanent changes to the object, such as burning, it can be considered a chemical reaction.
Also when there is bubbling or fizzing.
- A new substance may be created
- A change or peak in energy occurs.
- change in appearance of substance(s)
- Temperature change
- Precipitate
- Color change
You can tell when a chemical reaction occurs when there are changes in properties, a color change, and when the changes in properties precipitate.
The color change, Fomation of a precipitate, Formation of gas, and Temperature change
Evolution of a gas
heat/ energy
precipitate forms
color change
evolution of light
You could know by the color change, temperature change, a new substance may be created, etc..
First it changes into a complete different substance
Second it changes energy
Third it may change color
Fourth a solid may appear when two solutions are mixed together
Fifth is a gas might be produced from solids or liquids.
the smell and size.
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The following observations can help you to determine whether a chemical reaction has occurred:
- change of odour (smell)
- change of colour
- change in temperature, e.g. the production or loss of heat.
- change of form, e.g. burning paper
- light, heat, or sound is given off.
- formation of gases, often appearing as bubbles.
- formation of a precipitate (insoluble particles that usually sink to the bottom)
- the decomposition of organic matter, e.g. food rotting
- evident apparition of a new substance with a new chemical formula
There are quite a few indicators that a chemical change may have occurred. These include;- Change in color or luster. The release of gas or vapor. (noticeable odor or formation of bubbles) Change in temperature. (either cooling down or heating up) Formation of a precipitate. The release of heat and/or light & sound. A change in volume. The melting point or boiling point changes. A change in electrical conductivity occurs. A change in any distinctive chemical or physical properties occurs. Not all of these changes are necessarily proof of a chemical change, but they are a good indication and a starting point for further investigation. e.g. ruling out physical changes.
What else can I help you with?
What is the predicted organic product for the reaction?
The predicted organic product for the reaction is the compound that forms as a result of the chemical reaction taking place.
What evidence shows that a chemical reaction has taken place when you burn coal?
Evidence that a chemical reaction has taken place when burning coal includes the release of heat and light, the production of carbon dioxide and other combustion byproducts, and the change in the physical properties of the coal, such as the formation of ash.
What is the evidence that a chemical reaction took place when zinc mixed with HCl?
Evidence that a chemical reaction took place when zinc mixed with HCl includes the production of hydrogen gas bubbles, formation of zinc chloride as a product, and an increase in temperature of the reaction mixture due to the exothermic nature of the reaction. Additionally, the disappearance of the solid zinc as it undergoes dissolution is another indication that a chemical reaction has occurred.
What evidence do you have that a chemical reaction took place?
Evidence of a chemical reaction includes the formation of a new substance with different properties, changes in color, the release of gas or heat, or the formation of a precipitate. Additionally, changes in mass due to the rearrangement of atoms in the reactants can also indicate a chemical reaction has occurred.
What is the evidence that a chemical reaction took place when silver nitrate was mixed with ammonium chloride?
The evidence that a chemical reaction took place when silver nitrate was mixed with ammonium chloride is the formation of a white precipitate of silver chloride. This indicates that a chemical reaction occurred between the silver ions from silver nitrate and the chloride ions from ammonium chloride, resulting in the insoluble silver chloride. Additionally, the solution may turn cloudy or there may be a color change, further supporting the occurrence of a chemical reaction.
What evidence is there to show that a chemical reaction has taken place when an egg is cooked?
The change in color indicates that a chemical reaction has taken place.
How is a precipitate evidence for a chemical reaction?
A precipitate forms when two aqueous solutions react to produce an insoluble solid. The formation of a precipitate indicates that a chemical reaction has occurred, as the reactants have undergone a change in chemical composition to produce a new substance with different physical properties. This is observable evidence of a chemical change taking place.
What changes gives NO evidence that a chemical reaction has taken place?
Changes such as a change in state (solid to liquid), change in color, change in odor, change in solubility, or change in temperature do not provide direct evidence that a chemical reaction has occurred. These changes can be indicative of a physical change rather than a chemical change. To confirm a chemical reaction, additional evidence such as the formation of new substances, evolution of gas, or consumption of reactants is necessary.
What evidence that a chemical reaction has taken place would a living thing show?
work
What is the products of a chemical reaction?
The products of a chemical reaction are the substances that are formed as a result of the reaction taking place. These products can be different compounds or elements from the reactants that were present before the reaction occurred.
What is the predicted organic product for the reaction?
The predicted organic product for the reaction is the compound that forms as a result of the chemical reaction taking place.
What evidence shows that a chemical reaction has taken place when you burn coal?
Evidence that a chemical reaction has taken place when burning coal includes the release of heat and light, the production of carbon dioxide and other combustion byproducts, and the change in the physical properties of the coal, such as the formation of ash.
Which is indicated if a gas forms when two or more substances are mixed?
a chemical reaction has taken place.
Bubbling present during a chemical reaction is evidence of what?
Bubbling present during a chemical reaction is evidence of a gas being produced. The formation of gas bubbles indicates that a chemical change is taking place, often as a result of a reaction between two or more substances.
What type of chemical reaction occurs when electrons are shared?
no chemical reaction takes place . when electrons are shared it is known as covalent bond
What is the evidence that a chemical reaction took place when zinc mixed with HCl?
Evidence that a chemical reaction took place when zinc mixed with HCl includes the production of hydrogen gas bubbles, formation of zinc chloride as a product, and an increase in temperature of the reaction mixture due to the exothermic nature of the reaction. Additionally, the disappearance of the solid zinc as it undergoes dissolution is another indication that a chemical reaction has occurred.
Is burning newspaper a physical change?
Yes, burning newspaper is a chemical change because it undergoes a chemical reaction (combustion) that changes its chemical composition. The heat and flame produced during burning are evidence of this chemical reaction taking place.
