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irga5000 [103]
3 years ago
5

Which of the following is a chemical change?

Physics
2 answers:
e-lub [12.9K]3 years ago
4 0
A screw driver rusting when left in a pail of water is a chemical reaction
Kisachek [45]3 years ago
4 0

Answer:

a screwdriver rusting when left in a pail of water

Explanation:

In case of chemical change we can say that there must be a chemical reaction due to which there will be a change in the chemical reactants.

As we can see the given options

1). wind breaking down a rock into smaller pieces

There is no chemical reaction between them and it just a physical change of big size to smaller size

2). a leaf falling off of a tree during a storm

As we know that here also leaf detach from the tree so there is only physical change again.

3). a screwdriver rusting when left in a pail of water

Here we will have a chemical change due to which iron made its oxide due to chemical reaction of iron and oxygen

4). a block of ice melting in the sun

This is also physical change in which water molecules change from its solid state to liquid state

So here correct answer will be

a screwdriver rusting when left iwind breaking down a rock into smaller pieces

a leaf falling off of a tree during a storm

a screwdriver rusting when left in a pail of water

a block of ice melting in the sunwind breaking down a rock into smaller pieces

a leaf falling off of a tree during a storm

a screwdriver rusting when left in a pail of water

a block of ice melting in the sunwind breaking down a rock into smaller pieces

a leaf falling off of a tree during a storm

<em>a screwdriver rusting when left in a pail of water </em>

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1. For a reaction to occur, energy must be
amm1812

For a reaction to occur, energy must be absorbed to break chemical bonds

<u>Explanation:</u>

Reactions can be classified as chemical reaction, nuclear reaction, thermal reaction. So in these three reaction types, the nature of energy will only be varying.

But in order to execute a reaction, there should be breaking of existing bonds and then formation of new bonds. So for breaking of the bonds of reactants, energy should be absorbed from the surrounding.

Then the extra energy will be released after forming the products. Thus, the process of absorption of energy will lead to endothermic process and the process of releasing of energy will lead to exothermic reaction. So for a reaction to occur, energy must be absorbed to break the chemical bonds.

8 0
3 years ago
Help with these questions please?
egoroff_w [7]

Answer:

5. dispersion

6. 49.8°

Explanation:

5. Dispersion is the name given to the phenomenon of light of different wavelengths being bent differently. A rainbow is the result of light from a point source (the sun) being spread out by wavelength (color), a nice example of dispersion.

___

6. n = 1.31 is the ratio of the sine of the angle of refraction to the sine of the angle of incidence (for light passing to a medium of n = 1). When the angle of refraction is 90°, the angle of incidence is the "critical angle." So, ...

sin(90°)/sin(critical) = 1.31

critical angle = arcsin(1/1.31) ≈ 49.8°

8 0
3 years ago
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melamori03 [73]
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In other words, energy has to be conserved in every reaction.
4 0
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Is work being done on a barbell when a weight lifter is holding the barbell<br> over his head?
Artemon [7]

Answer:

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Semenov [28]

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4 0
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