Yes!
Yes, water weighs more than dirt. This is because water has a higher density compared to dirt, which means that a given volume of water will weigh more than the same volume of dirt.
Suppose the weight of the tank is T pounds. Then the weight of the liquid is (500 - T) pounds. The same volume of water will weight (500 - T)/0.8 = 1.25*(500 - T) pounds = 625 + 1.25T pounds.
That converts to 4000 pounds which is the same as 2 tons. Pounds is a unit of mass/weight. Gallons is a liquid measure. They do not convert cleanly. The density of the liquid being measured can make a big difference. If the liquid is water, there is 8 pounds to a gallon.
Flour and water are two substances whose weights are referenced to the same system of weights ... the avoirdupois system. Therefore the "pounds" used for each of them are the same pound. So 155 pounds of flour and 155 pounds of water have exactly the same weight, namely 155 pounds. There's no way to tell them apart using a scale.
To make 37000 pounds of steam, you would need 37000 pounds of water. This is because steam is simply water in the gas phase, so the weight of the steam would be equal to the weight of the water used to generate it.
No. If the water doesn't overflow, then the addition of the fish will increase the total weight of the tank and its contents by 50 pounds.
Both buckets weigh the same, 10 pounds each. The weight of the contents (water or apples) does not affect the weight of the buckets.
The same reason pressure builds up when you pile a thousand pounds of dirt onto someone. If you are 100 feet under water you are under many tons of water. Good thing all of that weight isn't directly exerted onto you, but spread out evenly in the ocean.
Multiply pounds by 16 to get the same weight expressed in ounces.
Dirt weighs more than water because dirt is denser than water. Water has a density of 1 gram per milliliter, while dirt can vary in density depending on its composition. Thus, a given volume of dirt will generally weigh more than the same volume of water.
They weigh the same, both are 100 pounds in weight.
That isn't a matching conversion. Pints are a measure of liquid volume. Pounds is a measure of weight/mass. They don't convert directly because of density. If you weighed the same as water, you would be 200 pints. But the human body is lighter than water, so it would be more, say 220 pints.