According to the statement there is a force of repulsion between the two objects. Remember that two objects must have the same charge so that they repel each other. In this way if the tape is repelled by a plastic pen that is negatively charged, this allows us to appreciate that the tape is also negatively charged. Now if the tape repels the sphere, therefore the sphere is also negatively charged.
Under these considerations the correct answers would be
2. Sodium ions from the salt water on your hand moved onto the sphere
4. The excess negative charge from the sphere spread out all over your body
6. Electrons from the sphere moved into the salt water on your skin, where they reacted with sodium ions
7. After you touched it, the metal sphere was very nearly neutral.
The process of flask becoming cold is due to endothermic reaction.
Answer: Option B
<u>Explanation:</u>
So two kinds of heat transfer can be possible in any chemical reaction. If the sample is considered as system and the sample container is considered as the surrounding, then heat transfer can occur between them.
If the heat is transferred from the surrounding to the system , then it is an endothermic reaction. And in those cases, the sample holder will be becoming colder. This is because the heat from the surrounding that is the container will be utilized to complete the reaction.
While when there is transfer of heat from the system to surrounding , it will be exothermic reaction and the beaker will be getting hot in this process. So in the present case, the container is becoming cold because of occurrence of endothermic process.
Im afraid i cant help u if we can’t see the image u r working with. could u provide an image of the question?
Answer:
c. expanded polyurethane
Explanation:
Thermal performance of a building fabric is measured in terms of heat loss and is expressed as U-value or R-value. U-value is the rate of heat transferred through a structure divided by the difference in temperature across the structure with a unit of measurement of W/m²K.You can calculate the U-value of a by getting the reciprocal of the sum of thermal resistances , R, making the building material.
If you have the value of R, then U=1/R
Material size R U
plywood 1" 1.25 0.8
Poured concrete 2" 0.99 1.010
Expanded polyurethane 1" 6.5 0.1538
Asbestos shingles 1" 0.03 33.33
The material with lowest U-value is expanded polyurethane
