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3 years ago

Which most likely indicate a chemical change has occurred ?

1 answer:

5 0

If a new substance suddenly appears that wasn't there originally,
then a chemical change has occurred.

Like for example, (this is the only example I can think of right now):

-- You leave your bicycle outside in the rain, and it gets wet, and
a few days later there's some rust on it.

-- You scrape off some of the rust, take it to school, give it to the
Chemistry teacher, and ask her to analyze it and tell you what it
is. Later that day, she tells you it's a substance called "Iron oxide".

-- Where did that come from ? There was no iron oxide there.
There was only iron in the bicycle, and air, and water.

-- The iron oxide formed from a chemical change when the iron
on the surface of the bike combined with some of the oxygen in
the air, and molecules of a new substance were created. (For
some reason, the presence of water makes this chemical reaction
go faster.)

You might be interested in

Suppose the line on a distance-versus-time graph and the line on a speed-versus-time graph are both slanted straight lines going

lesya [120]

No, because the distance-time would show a constant velocity but the velocity-time graph shows an increasing velocity.

4 0

4 years ago

A 99.5 N grocery cart is pushed 12.9 m along an aisle by a shopper who exerts a constant horizontal force of 34.6 N. The acceler

Romashka [77]

1) 9.4 m/s

First of all, we can calculate the work done by the horizontal force, given by

W = Fd

where

F = 34.6 N is the magnitude of the force

d = 12.9 m is the displacement of the cart

Solving ,

W = (34.6 N)(12.9 m) = 446.3 J

According to the work-energy theorem, this is also equal to the kinetic energy gained by the cart:

$W=K_f - K_i$

Since the cart was initially at rest, $K_i = 0$ , so

$W=K_f = \frac{1}{2}mv^2$ (1)

where

m is the of the cart

v is the final speed

The mass of the cart can be found starting from its weight, $F_g = 99.5 N$ :

$m=\frac{F_g}{g}=\frac{99.5 N}{9.8 m/s^2}=10.2 kg$

So solving eq.(1) for v, we find the final speed of the cart:

$v=\sqrt{\frac{2W}{m}}=\sqrt{\frac{2(446.3 J)}{10.2 kg}}=9.4 m/s$

2) $2.51\cdot 10^7 J$

The work done on the train is given by

W = Fd

where

F is the magnitude of the force

d is the displacement of the train

In this problem,

$F=4.28 \cdot 10^5 N$

$d=586 m$

So the work done is

$W=(4.28\cdot 10^5 N)(586 m)=2.51\cdot 10^7 J$

3) $2.51\cdot 10^7 J$

According to the work-energy theorem, the change in kinetic energy of the train is equal to the work done on it:

$W=\Delta K = K_f - K_i$

where

W is the work done

$\Delta K$ is the change in kinetic energy

Therefore, the change in kinetic energy is

$\Delta K = W = 2.51\cdot 10^7 J$

4) 37.2 m/s

According to the work-energy theorem,

$W=\Delta K = K_f - K_i$

where

$K_f$ is the final kinetic energy of the train

$K_i = 0$ is the initial kinetic energy of the train, which is zero since the train started from rest

Re-writing the equation,

$W=K_f = \frac{1}{2}mv^2$

where

m = 36300 kg is the mass of the train

v is the final speed of the train

Solving for v, we find

$v=\sqrt{\frac{2W}{m}}=\sqrt{\frac{2(2.51\cdot 10^7 J)}{36300 kg}}=37.2 m/s$

7 0

4 years ago

Which of the following is TRUE about inertia based on Galileo’s conception? A. Inertia is responsible for the continuous acceler

Arlecino [84]

Inertia is a property of all the objects. Galileo stated that inertia is proportional to mass. Therefore, the answer is D.

5 0

1 year ago

The Moon orbits the Earth once in about _______.

Bas_tet [7]

Answer:

The moon orbits the Earth once in about 27.332 days.

7 0

3 years ago

Read 2 more answers

with respect to air the refractive index of ice is 1.31 and that of rock salt is 1.54 calculate the refractive index of rock sal

abruzzese [7]

Answer:

1.17

Explanation:

Given that,

The refractive index of ice wrt air = 1.31

The refractive index of rock salt wrt air = 1.54

We need to find the refractive index of rock salt with respect to ice.

We know that,

refractive index = (speed of light in air or vaccum)/( speed of light in that medium)

So,

The speed of light in ice = c/(1.31)

The speed of light in rock salt = c/(1.54)

So, the refractive index of rock salt with respect to ice is :

$\mu=\dfrac{1.54}{1.31}\\\\=1.17$

So, the required refractive index of rock salt wrt ice is 1.17.

4 0

3 years ago