51. What is the mass of 4.2 kg of gold when it is transferred to a planet having twice the gravity of earth?
71. You have a mixture of salt and sand that must be separated by using physical changes only. Describe what you would do to prepare dry samples of the two constituents of the mixture.
51. Wouldn't the mass be 2 x 4.2 kg?
71. Salt and sand. Salt dissolves in water, sand doesn't. Couldn't you use that physical property to separate them?
Mass and weight are two different things. It is true that the object would weigh twice as much, but the mass would remain the same, as it is independent of gravity.
Think of mass as a measure of the amount of matter in an object. Weight is a measure of force (F=ma).
I agree on the other one. Salt (NaCl) is very soluble in water, and sand (SiO2) is mostly insoluble.
Ian is absolutely correct. I missed that the problem asked for mass and not weight.
To find the mass of the gold on a planet with twice the gravity of Earth, we need to understand the concept of weight and mass. Weight is the force exerted on an object due to gravity, while mass is the measure of the amount of matter in an object.
Since we know the mass of the gold is 4.2 kg, the weight on Earth can be calculated using the formula:
Weight = mass * acceleration due to gravity
On Earth, the acceleration due to gravity is approximately 9.8 m/s^2. So, the weight of the gold on Earth would be:
Weight on Earth = 4.2 kg * 9.8 m/s^2 = 41.16 N (Newtons)
Now, to find the weight of the gold on a planet with twice the gravity of Earth, we can simply double the acceleration due to gravity:
Acceleration due to gravity on the new planet = 2 * 9.8 m/s^2 = 19.6 m/s^2
Finally, we calculate the weight on the new planet using the same formula:
Weight on the new planet = 4.2 kg * 19.6 m/s^2 = 82.32 N
Therefore, the mass of 4.2 kg of gold when transferred to a planet with twice the gravity of Earth would be 82.32 N.
Regarding the mixture of salt and sand, there are several ways to separate them using physical changes. One common method is to use the differences in solubility between the two substances.
First, we can dissolve the mixture in water since salt is soluble while sand is not. By adding water and stirring the mixture, the salt will dissolve, while the sand will remain as a solid.
Next, we can use filtration to separate the liquid solution containing salt from the sand. Filtration involves passing the mixture through a filter, which will trap the solid sand particles while allowing the liquid to pass through. The result would be a mixture of water with dissolved salt and a solid filter residue containing the sand.
To obtain dry samples of the two constituents, we can follow these steps:
1. Evaporation: Heat the liquid solution containing salt to evaporate the water. As the water evaporates, the salt will remain behind as solid crystals.
2. Filtration: Once the liquid is completely evaporated, use filtration again to separate the solid salt crystals from any remaining impurities.
3. Drying: Allow the collected salt crystals to air dry or use gentle heating to remove any remaining moisture.
4. The result will be dry salt crystals. The remaining residue collected during filtration will be dry sand.
By using these physical changes (dissolving, filtration, evaporation, and drying), we can successfully obtain dry samples of salt and sand from the mixture.