Answer: Electricity
Explanation: Electricity is the movement of matter. not matter itself
Answer:
To decrease the solubility of the organic product in water.
Explanation:
Methyl benzoate is prepared via <em>Fischer esterification </em>reaction between benzoic acid and methanol in the presence of a mineral acid. The following steps are involved:
- Benzoic acid is dissolved in methanol in a round bottom flask.
- Concentrated sulphuric acid is added and heated under reflux on a steam bath
- Reaction is poured into ice, reaction flask is rinsed with dichloromethane. Layers collected in a test tube.
- Dichloromethane layer is then washed with first sodium carbonate solution(this is done inorder to neutralize and remove the residual benzoic acid) and then with sodium chloride solution(to decrease the solubility of the organic product in water).
- Then Dichloromethane solution is dried over magnesium sulphate.
- Dichloromethane is removed via distillation on a steam bath.
- Collect distillate in a vial on a heating mantle.
Answer: A) The mass of the cup of frozen water is 12 grams which means the mass did not change
Explanation:
The mass of water did not change, because the amount of matter is the same: by the law of mass conservation you can assure that the mass of water (12 grams) is the same at the begining than the end.
Both in the physical changes (as in the case of the changes in the phases of the matter) and in the chemical changes, the law of conservation of the mass is obeyed. Therefore, assuming that the liquid water did not spill from the sealed container during the night, the mass remained constant (12 grams).
Regarding the fact that Josh noticed the cup had cracked on its sides, you must observe that water is an exception to the common behavior of the matter: most substances shrink when pass from liquid state to solid state due to the fact that the particles (atoms, molecules or ions) lose kinetic energy and they the approach each other occupying less space.
Being the density inversely relatated to the volume (density = mass / volume), this increase on volume means that the substances will increase its density when pass from liquid to solid.
But water is a remarkable exception. Water density reaches its maximum at about 4°C, which means that solid water (0°C) is less dense than liquid water.
Hence, ice (solid water) will ocuppy more space (more volume) than the same amount of liquid water, which is the reason why the liquid water in the plastic cup expanded when it froze, cracking the cup.
No, it is a physical change. Changing states is physical.A chemical change is to change the nature of something by changing it's chemical makeup.
The answer is "A. a pure substance can be separated by chemical means, while a mixture can be separated by physical means". A pure substance only has one type of substance, whereas a mixture has more than one. A pure substance therefore, can only be separated chemically, because it is not two things mixed together, whereas a mixture can be separated physically because there are multiple substances.
