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Building a tower out of magnetic blocks and water vapor condensing on a bathroom mirror are only physical changes.
A physical change is easily reversible. It does not involve a change in the composition of a substance.
A tower built out of magnetic blocks can easily be pulled apart and water that condensed on a bathroom mirror can easily change back to vapour by heating.
All these are possible because the both processes are only physical changes.
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Explanation:
From the attached phase diagram, one can easily make out the phase in which water exists. Matter generally exists in three physical states which are solid, liquid and gas. Water is a unique compound that can exists in these three states at a given temperature and pressure.
From the attached phase diagram,
- point O is the triple point where the three phases of pure substance co-exists.
- The areas between the curves points at a single phase of matter. Y is a water vapor.
- The lines on the curve denotes two equilibrium phases. For example; X is a phase contain ice and melt water.
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B. normal contact force acts in the opposite direction as of weight, hence A is out. C is out as if normal contact force is lesser than the weight, the object would be sinking into the ground due to net force of the weight. D is out as if normal contact force is greater than the weight, the object would be flying upwards.
Answer:
1.57×10²³ molecules
Explanation:
Given data:
Number of molecules of ethanol = ?
Volume of ethanol = 15.0 mL
Density of ethanol = 0.789 g/mL
Solution:
Mass of ethanol :
Density = mass/ volume
0.789 g/mL = mass/ 15.0 mL
Mass = 0.789 g/mL× 15.0 mL
Mass = 11.84 g
Number of moles of ethanol:
Number of moles = mass/molar mass
Number of moles = 11.84 g / 46.07 g/mol
Number of moles = 0.26 mol
1 mole contain 6.022×10²³ molecules
0.26 mol × 6.022×10²³ molecules / 1mol
1.57×10²³ molecules
