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3 years ago

What are some examples of physical changes?

2 answers:

5 0

Answer: Melting of ice to water is a physical change. Evaporation, Freezing are also physical change. Cutting of wood, breaking of glass are also examples. Any change in size and phase but does not change its chemical composition is an example of a physical change.

Explanation:

Ludmilka [50]3 years ago

3 0

Some examples of physical changes are:

Breaking a glass

Chopping wood

Tearing paper

Mixing sand and water

Melting an ice cube

These all are physical changes because the composition of the matter does not change.

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A sample of metal has a mass of 24.64 g, and a volume of 5.91 mL. What is the density of this metal?

dlinn [17]

Answer:

$\boxed {\boxed {\sf 4.17 \ g/mL}}$

Explanation:

We are asked to find the density of a metal. Density is the mass per unit volume. It is calculated by dividing the mass by the volume.

$\rho= \frac{m}{v}$

The mass of the metal sample is 24.64 grams and the volume is 5.91 milliliters. We can substitute these values into the formula.

m= 24.64 g
v= 5.91 mL

$\rho=\frac{24.64 \ g }{5.81 \ mL}$

Divide.

$\rho= 4.169204738 \ g/mL$

The mass measurement has 4 significant figures the volume measurement has 3 significant figures. Our answer for density must match the least number of significant figures, which is 3.

For the number we calculated, that is the hundredth place. The 9 in the thousandth place tells us to round the 6 up to a 7.

$\rho \approx 4.17 \ g/mL$

The density of this metal is approximately <u>4.17 grams per milliliter.</u>

3 0

3 years ago

The quantum yield of light-induced chemical reactions (called photochemical reactions) measures the efficiency of the process. T

marissa [1.9K]

Answer:

1.9×10^20

Explanation:

ϕ = number of reaction events /number of photons absorbed

ϕ= 0.26

Energy= power× time

885×10^-3×10×60= 531J

But E= nhc/λ

n= number of photons

h= planks constant

c= speed of light

λ= wavelength

n= Eλ/hc

n= 531×280×10^-9/6.6×10^-34 ×3×10^8

n= 7.5×10^20

Therefore

From

ϕ = number of reaction events /number of photons absorbed

Number of reaction events= 0.26×7.5×10^20

= 1.95×10^20

3 0

4 years ago

This is a quiz and it’s due today

Romashka [77]

The answer is the el second one since it is a physical change

7 0

3 years ago

Collectiveness leads to a good society? how

ivann1987 [24]

Answer:

A good society has a transparent talk, they share all matters related to the society, hence everyone knows what's going on. This is why collectiveness leads to a good society.

If my answer helped, kindly mark me as the brainliest!!

Thank You!!

8 0

3 years ago

Im Stuck on this question for My Science homework

yarga [219]

Answer:

it's not clear

Explanation:

7 0

3 years ago