[Guest]

Old Mr. Tidy was found dead in his study by Mr. Fiend. Mr. Fiend recounted his dismal discovery to the police. "I was walking by Mr. Tidy`s house when I thought I would just pop in for a visit. I noticed his study light was on and I decided to peek in from the outside to see if he was in there. There was frost on the window so I had to wipe it away to see inside. That is when I saw his body. So I kicked in the front door to confirm my suspicions of foul play. I called the police immediately afterward." The officer immediately arrested Mr. Fiend for the murder of Mr. Tidy. How did he know Mr. Fiend was lying?

[Thalia]

Wouldn't frost be on the inside of the window? If so, he couldn't have wiped it away.

[Guest]

The frost is nothing more than condensation which forms on the inside of the glass due to the temperature change. Arrest him! He's the killer.

[Guest]

frost on the outside of the window? unless it was so snowy that it literally accummulated on the outside, this is a 'dead' giveaway. And, if it were that snowy, it's highly unlikely he would've seen the light anyhow.

[Brandonb]

I think I'm stumped. I wiped the frost off the outside of my car windows this morning, so the phrase "There was frost on the window so I had to wipe it away to see inside." is nothing more than a red herring... unless of course there was evidence that no one had wiped the window... or none of the windows were frosted.

Actually, now that I think about it, Frost does not form on either side of warm glass. So if the lights were on, then the electricity was on. If the electricity was on, then the heat was likely on. If the heat was on, then the glass would not have frost unless it was CRAZY cold outside and snowing. In which case, I wonder if there were footprints in the snow outside Tidy's window?

[bonanova]

I think I'm stumped. I wiped the frost off the outside of my car windows this morning, so the phrase "There was frost on the window so I had to wipe it away to see inside." is nothing more than a red herring... unless of course there was evidence that no one had wiped the window... or none of the windows were frosted.

Actually, now that I think about it, Frost does not form on either side of warm glass. So if the lights were on, then the electricity was on. If the electricity was on, then the heat was likely on. If the heat was on, then the glass would not have frost unless it was CRAZY cold outside and snowing. In which case, I wonder if there were footprints in the snow outside Tidy's window?

I grew up in cold-weather climate and never thought of the apparent contradiction.

[1] Frost does form on the inside of a house window - I licked it as a child.

[2] Frost does form on the outside of a car window - I scraped it as an adult - still do.

Why the difference? What are the two mechanisms?

[1] is easy. A cold window lowers the temperature of nearby inside air beyond its dew point, making water, and continues cooling it, making ice. Same thing happens to the outside of a bottle or glass containing a gold beverage in a warm humid day.

[2] is different. On cool mornings, but with temperature above freezing, dew forms on the ground, car windows, etc. If the temperature is low enough, the dew becomes frost. In [1], a surface cooler than the dew point gets wet. With dew and frost, it's not the surface that cools the air and receives moisture. Rather, the air is cooled by natural causes at night [radiation loss into the sky is one mechanism] squeezing moisture [mostly] onto upward-facing surfaces. The ground, grass, car windshields more than [side-facing] car windows. As a secondary process, the moisture freezes into frost. Or, the humidity goes directly to the ice state when the air cools below its frost point.

a propos the OP, frost does not form on the outside of windows of a heated house.

[Guest]

Probably the ppl here are right but my opinion would be that if Mr. Fiend killed the man the hatch of the door should be opened(he can't lock the door from the inside),but according to his statement he KICKED the door,so the police should see that the hatch is broken. There is the discrepancy.

[Guest]

Probably the ppl here are right but my opinion would be that if Mr. Fiend killed the man the hatch of the door should be opened(he can't lock the door from the inside),but according to his statement he KICKED the door,so the police should see that the hatch is broken. There is the discrepancy.

This was my first thought, too.

[Guest]

Frost would not form on the outside of the window, especially that the light was on, which would cause the temperature in the room to be higher than outside. Moisture in the room would be in the form of gas, but (and here is an assumption that it was a frosty night) temperature would drop near the window to cause the moisture to condense and freeze inside. Although it would be possible to melt the ice from outside by applying the constant heat for a time, Mr Fiend says that he "wiped it away", which of course was not possible. Obviously he didn't pay attention in his physics lessons!

[Guest]

Classic one.The window frost is from the inside.If it was from the outside it would mean it was very hot outside and freezing inside !

[Guest]

is it because the study is on the second floor?

[Guest]

Whether the frost was on the inside or on the outside doesn't matter because if it was frosty, he could not have seen the lights in the study on. There is the discrepancy.

As bonanova explained, frost could have been on either side of the window.

[Guest]

good job thalia. You all have some good ideas. but you see, you have to account for the insulation on the house. A car doesnt have that insulation.

[Guest]

Puzle Solved

[Guest]

sorry im trying to get this pol thing right

[Brandonb]

I grew up in cold-weather climate and never thought of the apparent contradiction.

[1] Frost does form on the inside of a house window - I licked it as a child.

[2] Frost does form on the outside of a car window - I scraped it as an adult - still do.

Why the difference? What are the two mechanisms?

[1] is easy. A cold window lowers the temperature of nearby inside air beyond its dew point, making water, and continues cooling it, making ice. Same thing happens to the outside of a bottle or glass containing a gold beverage in a warm humid day.

[2] is different. On cool mornings, but with temperature above freezing, dew forms on the ground, car windows, etc. If the temperature is low enough, the dew becomes frost. In [1], a surface cooler than the dew point gets wet. With dew and frost, it's not the surface that cools the air and receives moisture. Rather, the air is cooled by natural causes at night [radiation loss into the sky is one mechanism] squeezing moisture [mostly] onto upward-facing surfaces. The ground, grass, car windshields more than [side-facing] car windows. As a secondary process, the moisture freezes into frost. Or, the humidity goes directly to the ice state when the air cools below its frost point.

a propos the OP, frost does not form on the outside of windows of a heated house.

Very well explained Bona. It's been a long time!

[Guest]

If you really think about it

You can't wipe away frost with your bare hands or even with a glove! It would just be crystalized.