Physics, 13.10.2019 00:00, Haneendye123

Which would show an example of how physical changes are reversible? cutting a gold bar in two peices and then putting the pieces next to eachother. or burning a match and then relighting it. or melting tin and then cooling it into a mold. or combining sodium and chlorine to make the new material of table salt

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answered: queengenni

Melting tin and then cooling it into a mold is the process which showing physical changes are reversible.

Explanation:

Physical change:

The physical change is the change of shape, size or state of the substance. by physical change a new substance is formed. The physical change can be reversible.

Chemical change:

The change or rearrangement of atoms is there , the change is called the chemical change. which leads to the formation of new substance.

(A) The physical change which is not reversible is cutting a gold bar into pieces next to each other.

(B)Burning a match and then realigning is a chemical change as new substance are formed.

(C)Melting tin and then cooling it into a mold: This is a physical change and it is reversible as its original state is achieved again.

(D)Combination of sodium and chlorine to make the new material of table salt as it is a chemical change.

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answered: smcculleymcculley

melting tin and then cooling it into a mold

Explanation: Physical change is a change in which shape, size or state of the substance is changed and no new substance is formed. Physical changes can be reversed by

Chemical change: When there is a change in rearrangement of atoms which leads to the formation of the new substance.

a) Cutting a gold bar in two pieces and then putting the pieces next to each other: It is a physical change but it is not reversible as original state is not achieved again.

b) burning a match and then relighting it: This is a chemical change as new substances are formed.

c) melting tin and then cooling it into a mold: This is a physical change and is reversible as the original state has been achieved again.

d) combining sodium and chlorine to make the new material of table salt: It is a chemical change. $2Na+Cl_2\rightarrow 2NaCl$

answered: Guest

answer: the correct answer id option(d).

explanation:

snell's law refraction:

$\frac{n_2}{n_1}=\frac{sin \theta_1}{sin\theta_2}$

the angle of refraction = $\theta_2=38 ^o$

the angle of incidence = $\theta_1=?$

refractive index of air = $n_1$ = 1

refractive index of glycerol $n_2$ = 1.47

$\frac{1.47}{1}=\frac{sin\theta_1}{sin 38^o}, (sin38^o=0.61)$

$sin\theta_2=0.8967$

$\theta_2=24.2^o, (sin^{-1}0.8967=63.72^o)$

from the given options, the most closest answer to 63.72° is 65° of option (d).

answered: Guest

answer: you might love summer weather, but you don’t want it to feel like the sun is inside your car. but a hot car that just won’t seem to cool down might be a bigger of a problem than you think. your car relies on being at the right temperature.

explanation: