Help me check answers

[cookies]

1. To turn 50g of boiling water to steam requires

A. 50 Calories (210 Joules)

B. 500 Calories (2100 Joules)

C. 540 Calories (2270 Joules)

D. None above

 

2. If you were caught freezing in cold weather with only a candel for heat, you would be warmer in

A. an igloo

B. a car

C. a tent

D. a wooden house

 

3. It is possible to totally convert a given amount of energy into mechanical energy.

A. True

B. False

 

4. When a solid is changed to a liquid phase, the solid

A. absorb energy

B. release energy

C. neither

 

5. When work is done by a system and no heat added to it, the temperature of the system

A. Decrease

B. Increase

C. Remains unchanged

 

6. An inventor discovers a harmless and tasteless salt, which, when added to water changes its boiling point, the market value for this salt will be best if the salt

A. lower the boiling point of water

B. raises the boiling point of water

C. either raises or lowers the boiling point, as the food would be cooked either way.

 

7. A good asorber of radiation is a

A. good reflector

B. good emitter of radiation

C. poor emitter of radiation

 

8. The amount of energy ultimately converted to heat by light bulbs is about

A. 30%

B. 60%

C. 15%

D. 45%

E. 100%

 

9. Steam burns are more dangerous than burns caused by boiling water becuase steam

A. Gives the additional energy when it condenses

B. Has more energy per kilogram than boiling water

C. Both of these

D. neither of these

 

 

 

 

Answers for # 1 through #9 are D,A, B, A, A, B, B, E, C.

 

please correct me thxs

[Ndi]

1. 50 Cal. Though if it's BOILING water than technically it will evaporate itself . One cal raises 1 gram by one degree. 50 cals will rise 50g by one degree, assumingly over 100.

2. Igloo (best isolation). When lines with skin on the inside, it can keep you at 20 deg Celsius in a -50 environment. That is, T-shirt.

3. False. Some is always heat. You can convert nothing into nothing without heat loss.

4. Changing state to a higher level absorbs heat. (evaporation chills)

5. Decrease (Don't quote me). I don't completely understand the question (language). Does it apply the work inside? Outside?

6. If it increases boiling point. The applications in automotive cooling systems and heat pumps in general is going to make that person veeeery rich. As for cooking, food will cook faster if the water boils at a higher temperature, but the taste changes so it's open for debate.

7. C (IIRC)

8. IMHO, this is a bad question. Light bulbs convert approx 5% light and 95% heat. Fluorescent bulbs go as high as 20% light. Trick question? "Ultimately" ALL energy ANYWHERE finally ends up as heat sooner or later so i guess 100% is OK for any conversion. Is this a concept test or a memory test? No bulbs do even close to those numbers. OTOH, if they do 100% heat, where's the light coming from?

9. Steam burns because it is hotter than water (100 Deg Celsius). It is true it gives more energy when it condenses on skin but that is not really why it's bad. Both are technically correct, though. C?

 

Do NOT take this as expert advice.