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3 years ago

Help me with number 3 and 4 pleaseeeeeeeee

Physics

2 answers:

Andrej [43]3 years ago

6 0

i think its b cause if you were talking about ice it freezes the melts the evaporates to gas

Roman55 [17]3 years ago

3 0

Number three I think might be b

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Describe how velocity and speed are different

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Noise pollution can lead to the disruption of speech communication in children<br> true or false

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1. 412.9 g of dry ice sublimes at room temperature. a. What’s changing? --- sublimation b. What constant will you use? ----- 25.

hoa [83]

1. 236 kJ

a. The phase (or state of matter) of the substance: from solid state to gas state (sublimation)

b. The enthalphy of sublimation, given by: $\lambda=571 J/g$

c. The equation to use will be $Q=m\lambda$ , where m is the mass of dry ice and $\lambda$ is the enthalpy of sublimation

d. The energy is being absorbed, because the heat is transferred from the environment to the dry ice: as a consequence, the bonds between the molecules of dry ice break and then move faster and faster, and so the substance turns from solid into gas directly.

e. The amount of energy being transferred is

$Q=m\lambda=(412.9 g)(571 J/g)=2.36\cdot 10^5 J=236 kJ$

2. 165 kJ

a. The phase (or state of matter) of the substance: from gas state to liquid state (condensation)

b. The latent heat of vaporisation of water, given by $\lambda=2260 J/g$

c. The equation to use will be $Q=m\lambda$ , where m is the mass of steam that condenses and $\lambda$ is the latent heat of vaporisation

d. The energy is being released, since the substance turns from a gas state (where molecules move faster) into liquid state (where molecules move slower), so the internal energy of the substance has decreased, therefore heat has been released

e. The amount of energy being transferred is

$Q=m\lambda=(72.9 g)(2260 J/g)=1.65\cdot 10^5 J=165 kJ$

3. 3.64 kJ

a. Only the temperature of the substance (which is increasing)

b. The specific heat capacity of silver, which is $C_s = 0.240 J/gC$

c. The equation to use will be $Q=m C_s \Delta T$ , where m is the mass of silver, Cs is the specific heat capacity and $\Delta T$ the increase in temperature

d. The energy is being absorbed by the silver, since its temperature increases, this means that its molecules move faster so energy should be provided to the silver by the surroundings

e. The amount of energy being transferred is

$Q=m C_s \Delta T=(39.2 g)(0.240 J/gC)(412.9^{\circ}C-25.9^{\circ}C)=3641=3.64 kJ$

4. 89 kJ

a. Both the phase of the substance (from solid to liquid) and then the temperature

b. The latent heat of fusion of ice: $\lambda=334 J/g$ and the specific heat capacity of water: $C_s=4.186 J/gC$

c. The equation to use will be $Q=m\lambda + m C_s \Delta T$ , where m is the mass of ice, $\lambda$ the latent heat of fusion of ice, Cs is the specific heat capacity of water and $\Delta T$ the increase in temperature

d. The energy is being absorbed by the ice, at first to break the bonds between the molecules of ice and to cause the melting of ice, and then to increase the temperature of the water

e. The amount of energy being transferred is

$Q=m\lambda +m C_s \Delta T=(156.3 g)(334 J/g)+(156.3 g)(4.186 J/gC)(56.232^{\circ}C-0^{\circ}C)=8.9\cdot 10^4 J=89 kJ$

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3 years ago

In a nuclear power plant, the temperature of the water in the reactor is above 100°C because of what?

SVETLANKA909090 [29]

Answer:

The temperature of the water increases because the nuclear reactor heats it producing steam

Explanation:

The nuclear power plants are usually defined as those thermal plants where the nuclear reactors are used in order to generate heat that eventually leads to the rotating of the turbines and produces electricity. Here the nuclear reactor heats the water, and it increases above a temperature of 100°C, where this heat energy plays a key role in the entire process. It is an efficient method as it does not lead to the emission of any green house gases that are harmful to the environment.

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3 years ago

A force of 14 N acts on a 5 kg object for 3 seconds.

DiKsa [7]

Answer: a) 42Nm b) 8.4m/s

Explanation:

Impulse is defined as object change in momentum.

Since Force = mass × acceleration

F = ma

Acceleration is the rate of change in velocity.

F = m(v-u)/t

Cross multiply

Ft = m(v-u)

Since impulse = Ft

and Ft = m(v-u)... (1)

The object change in velocity (v-u) = Ft/m from eqn 1

Going to the question;

a) Impulse = Force (F) × time(t)

Given force = 14N and time = 3seconds

Impulse = 14×3

Impulse = 42Nm

b) The object change in velocity (v-u) = Ft/m where mass = 5kg

v-u = 14×3/5

Change in velocity = 42/5 = 8.4m/s

3 0

3 years ago