help with homework

[brendon557]

im helping my little sister with chemitsry homework and i have no idea how to do it and she is failing chemistry with a 49%, Does anyone know the answers?

Im gonna give a list of 5 things and i need to know if they are chemical or physical change and why.

thanks alot

1- A hotdog is cooked

2- Thousand island dressing and mayonaise are mixed to make "secret sauce" for hamburgers.

3- Water is boiled in preperation for making pasta.

4- Old ham goes bad in a refrigerator.

5- A rockstar gets a tatoo on his forehead.



thanks again.

[beeper]

1- Physical Change. The hotdog is not changing chemically, and it is possible to get the hotdog back to its origional state of being cold. (this may be wrong)

2- Physical change. You can separate thousasnd island dressing and mayo, although it would take a long time.

3- Chemical change. Once water turns into a gas, it can no longer be turned back.

4.- Chemical change. There is no way you can revive the ham in the fridge from being bad.

5- This one has me stumped.

[James_Potter]

1. Temperature change. The hot dog was cold, now it's hot.
2. Magical Change. How do they make that secret sauce??
3. Temperature change, same reason as number 1
4. Unfortunate change...I was looking forward to that ham....
5. Mental change. Think of what he's gonna look like when he's 60!! Haha!

Do your own homework, lazy Amerikan.

[aydan_evans]

3- Chemical change. Once water turns into a gas, it can no longer be turned back.

yeah it can, its called condensation isn't it?

[beeper]

yeah it can, its called condensation isn't it?


You cant physically take water molecules from the air, and put them in a pot to form water. A chemical change occurs in that situation, mainly because it is changing its state from a liquid to a gas. You can not make a liquid become a gas by using your hands.
Therefore, it is indeed a chemical change.

[James_Potter]

You cant physically take water molecules from the air, and put them in a pot to form water. A chemical change occurs in that situation, mainly because it is changing its state from a liquid to a gas. You can not make a liquid become a gas by using your hands.
Therefore, it is indeed a chemical change.
Geez, what are they teaching you kids in school these days?
A chemical change is when the molecular structure of a substance changes.
Whether water is in liquid, gas or solid form, it is still H2O, two atoms of Hydrogen and two atoms of Oxygen. So any change done to water where it remains H2O, is only physical. If something is done to water to change it to H2O2 or something would be a chemical change.

[dan de man]

im helping my little sister with chemitsry homework and i have no idea how to do it and she is failing chemistry with a 49%, Does anyone know the answers?

Im gonna give a list of 5 things and i need to know if they are chemical or physical change and why.

thanks alot

1- A hotdog is cooked

2- Thousand island dressing and mayonaise are mixed to make "secret sauce" for hamburgers.

3- Water is boiled in preperation for making pasta.

4- Old ham goes bad in a refrigerator.

5- A rockstar gets a tatoo on his forehead.



thanks again.
the hot dog one is a chemical change ,the hotdog is being cooked not heated

[ridingwithscissors]

Geez, what are they teaching you kids in school these days?
A chemical change is when the molecular structure of a substance changes.
Whether water is in liquid, gas or solid form, it is still H2O, two atoms of Hydrogen and two atoms of Oxygen. So any change done to water where it remains H2O, is only physical. If something is done to water to change it to H2O2 or something would be a chemical change.
so there.

[UniBrier]

the hotdog is being cooked not heatedLet's be frank about this.

The hot dog has already been cooked and then frozen. You jsut re-heat it it probably doesn't change much except it's warm again. You can cook it beyond that point and it will change from being charred, burnt, etc.

[Rubix]

2- Thousand island dressing and mayonaise are mixed to make "secret sauce" for hamburgers.


This here would be called an 'emulsion', physically combining two things that aren't meant to be combined. Oil and water....fat and proteins....it all can be done, just gotta know how and what temp. You can also break the emulsion easily too, with the temp, or how aggressive you are emulsifying the ingredients. They all will seperate on their own, but you can also speed up that process real easily.

[SqueakyOnion]

Let's be frank about this.

The hot dog has already been cooked and then frozen. You jsut re-heat it it probably doesn't change much except it's warm again. You can cook it beyond that point and it will change from being charred, burnt, etc.


Teacher could be referring to in the factory where the hot dog is being cooked. You're only assuming that the average joe is taking it out of the fridge and tossing it in the nuker.

I'd make a stink about it in class, and tell the teacher it could be either based on interpretation.

Cooking, I believe, would be a chemical change, and heating would not. Thus, open to interpretation...

[James_Potter]

The hotdog being heated is the same as the water being heated...if it's just warmed up a lot, it is still a hotdog and therefore physical. If it's heated too much and burns, then it's turned into ash, which is a different element, and therefore it is not a hotdog anymore, so it's a chemical change.

[kington99]

1- A hotdog is cooked

chemical change

2- Thousand island dressing and mayonaise are mixed to make "secret sauce" for hamburgers.

physical change, mixing of an emulsion as someone mentioned above

3- Water is boiled in preperation for making pasta.

physical change, molecules reamin unchanged only bonding between them, process is obviously reversible

4- Old ham goes bad in a refrigerator.

chemical, oxidation of molecules in meat

5- A rockstar gets a tatoo on his forehead.

physcial, ink is placed underneath the skin



and seriously some of the answers already posted are atrocious

[dan de man]

Let's be frank about this.

The hot dog has already been cooked and then frozen. You jsut re-heat it it probably doesn't change much except it's warm again. You can cook it beyond that point and it will change from being charred, burnt, etc.
wait I think this is a dialecticle difference between australia and america ,we barbacue a hot dogs and we call em sauseges

[jamessd]

and seriously some of the answers already posted are atrocious
I was going to say that before, but then I feared for my reputation.

But some are pretty demeaning.