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olya-2409 [2.1K]
3 years ago
10

A doorknob makes it easier for you to open doors because it is what type of simple machine?

Chemistry
1 answer:
vagabundo [1.1K]3 years ago
5 0

Answer: Wheel and Axle

Both of these work together to form a simple machine. You can't have one without the other.

If you try to turn just the axle itself, then you'll find it takes a lot of work. This is because the inertia of the axle wants to keep the object at rest. Also, you won't have a lot of torque due to the small radius compared to what a doorknob can offer.

Using a doorknob is like putting a (steering) wheel on an axle. This increases the radius and therefore increases the torque. You put in less work into the system and get more out of it.

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If constant heat is added to ice water, what changes will take place and at what temperatures?
EleoNora [17]

Answer:

Explanation:

When you heat ice, its temperature rises, but as soon as the ice starts to melt, the temperature stays constant until all the ice has melted. This happens because all the heat energy goes into breaking the bonds of the ice's crystal lattice structure.   :)

6 0
3 years ago
HELP PLEASE I HAVE A TEST TODAY AND I DON'T UNDERSTAND ANY OF THIS...
myrzilka [38]

Answer:

About 67 grams or 67.39 grams

Explanation:

First you would have to remember a few things:

 enthalpy to melt ice is called enthalpy of fusion.  this value is 6.02kJ/mol

  of ice  

 it takes 4.18 joules to raise 1 gram of liquid water 1 degree C

 water boils at 100 degrees C and water melts above 0 degrees C

 1 kilojoules is 1000 joules

  water's enthalpy of vaporization (steam) is 40.68 kJ/mol

  a mole of water is 18.02 grams

  we also have to assume the ice is at 0 degrees C

Step 1

Now start with your ice.  The enthalpy of fusion for ice is calculated with this formula:

q = n x ΔH    q= energy, n = moles of water, ΔH=enthalpy of fusion

Calculate how many moles of ice you have:

150g x (1 mol / 18.02 g) = 8.32 moles

Put that into the equation:

q = 8.32 mol x 6.02 = 50.09 kJ of energy to melt 150g of ice

Step 2

To raise 1 gram of water to the boiling point, it would take 4.18 joules times 100 (degrees C)  or 418 joules.

So if it takes 418 joules for just 1 gram of water, it would take 150 times that amount to raise 150g to 100 degrees C.  418 x 150 = 62,700 joules or 62.7 kilojoules.

So far you have already used 50.09 kJ to melt the ice and another 62.7 kJ to bring the water to boiling.  That's a total of 112.79 kJ.

Step 3

The final step is to see how much energy is left to vaporize the water.

Subtract the energy you used so far from what you were told you have.

265 kJ - 112.79 kJ = 152.21 kJ

Again q = mol x ΔH (vaporization)

You know you only have 152.21 kJ left so find out how many moles that will vaporize.

152.21 kJ = mol x 40.68  or   mol = 152.21 / 40.68  = 3.74 moles

This tells you that you have vaporized 3.74 moles with the energy you have left.

Convert that back to grams.

3.74 mol   x  ( 18.02 g / 1 mol ) = 67.39 grams

5 0
2 years ago
When salt is added to water, the entropy, S,
Dovator [93]

Answer:

C. number of particles

Explanation:

Entropy is the measure of disorderliness of a system. Remember that when you dissolve salt in water, you increase the number of particles in the solution. The greater the number of particles in solution, the greater the entropy of the  solution system.

Hence dissolution of a salt in water increases the entropy by increasing the number of particles in solution leading to the inequality; Ssolution > Swater + Ssalt.

5 0
3 years ago
Which molecule is a source of energy, a store of energy, and can mix with water?
yanalaym [24]

Answer:

Glucose

Explanation:

Glucose is a source of energy and it is stored in the body (in the form of glycogen) and it can also dissolve in water.

3 0
3 years ago
Briefly explain how magnetic behavior is related to the arrangement of valence electrons in the outer orbitals
olga nikolaevna [1]

Answer:

Elements with unpaired valence electrons in the outer orbital are paramagnetic. Elements that are predicted to exhibit paramagnetic behavior may exhibit ferromagnetic behavior. Elements that contain only paired valence electrons are diamagnetic.

3 0
3 years ago
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