what are physical and chemical changes explain with examples
Answers
Physical Change:
Changes which occur in the physical composition such as shape is called a physical change.
Some examples:
◉ Cutting of wood
◉ Breaking of bricks
◉ Freezing of water to make ice cubes
Chemical Change:
Changes involving change in the chemical composition are called chemical changes.
Some Examples:
◉ Burning of wood
◉ Digestion of food
◉ Cooking of food
your answer
Explanation:
temperature change, one substance, such as water is being heated. However, in this case, one compound is mixed in with another, and these reactants produce a product. When the reactants are mixed, the temperature change caused by the reaction is an indicator of a chemical change.
fireworks 4
Figure: Violent Reaction (Fireworks) with heat as a product
As an example of a exothermic reaction, if Fe2O3 is mixed with Al and ignighted (often with burning Mg), then the thermite reaciton is initiated
Fe2O3+2Al→2Fe+Al2O3+Heat(2)
This reaction generates heat as a product and is (very) exothermic.
However, physical changes can be exothermic or endothermic. The melting of an ice cube, which is endothermic, is a change in a physical property and not composition. Thus, it is a physical change.
Change in Color
A change in color is also another characteristic of a chemical reaction taking place. For example, if one were to observe the rusting of metal over time, one would realized that the metal has changed color and turned orange. This change in color is evidence of a chemical reaction. However, one must be careful; sometimes a change in color is simply the mixing of two colors, but no real change in the composition of the substances in question.
Metal Rusting
Oxidized balcony to the ocean 5
The reaction above is that of the rusting of iron.
4Fe+3O2+6H2O→4Fe(OH)3(3)
Noticeable Odor
When two or more compounds or elements are mixed and a scent or odor is present, a chemical reaction has taken place. For example, when an egg begins to smell, (a rotten egg) a chemical reaction has taken place. This is the result of a chemical decomposition.
Spoiled Egg
cracked egg
Formation of a Precipitate
The formation of a precipitate may be one of the most common signs of a chemical reaction taking place. A precipitate is defined to be a solid that forms inside of a solution or another solid. Precipitates should not be confused with suspensions, which are solutions that are homogeneous fluids with particles floating about in them. For instance, when a soluble carbonate reacts with Barium, a Barium Carbonate precipitate can be observed.
Test Tube
chemistry1
Reaction:
Ba2+(aq)+CO2−3(aq)→BaCO)3(s)(4)
For further information, please refer to Classification of Matter.
Formation of Bubbles
The formation of bubbles, or rather a gas, is another indicator of a chemical reaction taking place. When bubbles form, a temperature change could also be taking place. Temperature change and formation of bubbles often occur together. For example, in the following image, one can see a gas spewing. This is the formation of a gas.
Gas Formation
smoke
However, most reactions are much more subtle. For instance, if the following reaction occurs, one may notice Carbon Dioxide bubbles forming. If there is enough Hydrochloric Acid, bubbles are visible. If there isn't, one can't readily notice the change:
Na2CO3+2HCl→2NaCl+H2O+CO2(5)
hu viscosity image is also free to be duplicated as per permission of author on wikipedia.com.
Problems
1. Which of the following is a chemical reaction?
Freezing liquid Mercury
Adding yellow to blue to make green
Cutting a piece of paper into two pieces
Dropping a sliced orange into a vat of Sodium Hydroxide
Filling a balloon with natural air
2. Which of the following is a physical reaction?
Shattering Glass with a baseball
Corroding Metal
Fireworks Exploding
Lighting a match
Baking a cake
3. Which of the following is a chemical reaction?
Painting a wall blue
A bicycle rusting
Ice cream melting
Scratching a key across a desk
Making a sand castle
4. Which of the following is a physical reaction?
Frying an egg
Digesting carrots
A Macbook falling out of a window
Creating ATP in the human body
Dropping a fizzy tablet into a glass of water
5. Write C for Chemical Reaction or P for Physical Reaction.
Burning Leaves
Cutting Diamonds
Crushing a ledjjd