What indicates that a chemical reaction has taken place? Explain why

Physics

1 answer:

podryga [215]3 years ago

4 0

Answer:

Color. The changing of color of a substance is not necessarily an indicator of a chemical change. For example, changing the color of a metal does not change its physical properties. However, in a chemical reaction, a color change is usually an indicator that a reaction is occurring.21-Aug-2020

Liquid → Gas: Vaporization

Gas → Liquid: Condensation

Solid → Gas: Sublimation

Solid → Liquid: Melting

Explanation:

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Calculate the average speed of a gazelle that runs 140 meters in 5.0 seconds

bekas [8.4K]

140 m / 5 s = 28 meters per second

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2 years ago

a steam engine work on its vicinity 285 k heat is released with the help of 225 c energy absorbed to the system what is the effi

-Dominant- [34]

The efficiency of the steam engine is 78.9% because the rest of the work input is used to overcome friction.

<h3>What is efficiency of machines?</h3>

Efficiency of a machine expresses the useful work done by a a machine as a percentage.

Efficiency of a machine = work output/work input × 100 %%

The efficiency of machines are always less than 100% percent due to energy losses due to friction and heat.

For the steam engine:

Work output = 225 J

Work input = 285 J

Efficiency = 225/285 × 100% = 78.9 %

Therefore, the efficiency of the steam engine is 78.9% because the rest of the work input is used to overcome friction.

Learn more about efficiency of machines at: brainly.com/question/7536036

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1 year ago

A shell is fired at an angle of 35° above the horizontal at a velocity of 40 m/s. (a) What is it's speed at the highest point of

Fudgin [204]

Answer:

Part a)

$v_f = v_x = 32.77 m/s$

Part b)

T = 4.68 s

Explanation:

Part a)

Shell is fired at speed of 40 m/s at angle of 35 degree

so here we have

$v_x = 40 cos35 = 32.77 m/s$

$v_y = 40 sin35 = 22.94 m/s$

since gravity act opposite to vertical speed of the shell so at the highest point of its trajectory the vertical component of the speed will become zero

so at the highest point the speed is given

$v_f = 32.77 m/s$