Question

Name each activity or observation as either physical or chemical change.
1) Boiling water for pasta
2) Digesting food
3) Soda goes "flat"
4) Stretching a rubber band
5) Grilling a hamburger
6) Adding sugar to tea
7) Adding lemon to tea
8) Mowing the grass
9) The smell of perfume "wafts" across the room
10) Candle wax melts
11) Breaking glass
12) Making cement
13) Lighting a match
14) Water is absorbed by a paper towel
15) Firefly glows in the dark
16) Snow melts
17) Bleaching your hair
18) Turning on a light bulb
19) Milk goes sour
20) Shooting off fireworks

Answer 1

for u to fully understand this qst u sh'd kinow exactly wat those terms mean so heres a site to help with that.... http://www.mcwdn.org/chemist/pcchange.html

Answer 2

for more info the first is chemical since u cant change the pasta back to being its original state same as the second one

Answer 3

stretching a rubber band is physical since the rubber band doesnt change it physical state and it can go back to how it was ..c if u can tackle the other qsts then we confirm according this theory if they are right

Answer 4

GOOD JOB

Answer 5

You have a lot of changes on here indicating that you dont really understand the lesson you are in. I would suggest revisiting your book and one of the many amazing science websites out there. In short a physical change involves a change that doesn't really need to be permanent. It starts with 2 hydrogens and 1 oxygen and ends with 2 hydrogens and 1 oxygen (water switching between phases). Once a chemical change takes place it cant really be reversed. Think about when something rusts. It goes from a smooth metal to the rough red substance. the only way to get rid of it is to file it off and hope the rest doesn't rust too.

Answer 6

Physical: boiling, soda going flat, stretching the rubber band, dissolving sugar or lemon in tea, mowing the grass, diffusion of perfume, melting wax, absorption of water, melting of snow, turning on of light bulb.

All the rest are chemical, with the exception of breaking glass, which is a little ambigious. The problem is that to the extent the fracture happens along crystal grain boundaries, this is a physical change, but to the extent Si-O chemical bonds are broken, it is technically a chemical change. The difficulty is that from certain perspectives, as piece of glass can be regarded as one giant molecule, and therefore breaking it is technically a chemical change. I have no idea how your instructor wants it answered.

Chemical change is any change in which there is a chemical reaction -- that is, in which chemical bonds between atoms are made, broken, or (usually) both. Generally some substances are destroyed and some new ones are created, although there are some ambiguous cases, like the breaking of glass (or diamond), or the evaporation of a salt.

Everything that is not a chemical change is a physical change. So, to distinguish, look for changes that suggest a chemical reaction is taking place, and one substance is turning into another. For example, when milk goes sour, its taste changes, and what you taste are the various chemical compounds in the milk. If you get a new sour taste, that tells you a new substance has been created. A chemical reaction has taken place.

Another useful helpful fact is that any combustion -- e.g. fire -- always involves a chemical reaction, because one substance (the fuel) is destroyed, and another (smoke, gases, and ashes) are creaeted.