00:01
Hi there.
00:03
This question is asking about physical changes versus chemical changes.
00:09
So let's talk about these two terms for a moment before we proceed.
00:13
Physical change is exactly that.
00:18
The matter is just changing physically.
00:21
You are not getting a new substance.
00:24
It'll still have the same formula.
00:33
For example, if we have ice, which is h2o solid, we can heat that up and it melts.
00:43
To liquid water, but the formula is still h2o.
00:47
It is still the same substance.
00:50
So that would be a physical change.
00:52
A chemical change, on the other hand, gives us new substances with new properties.
01:11
All right, so new substances, that means a new formula with new properties.
01:19
For example, let's stick with water here.
01:21
Let's say we start with liquid water, and we pass an electric current through it.
01:27
That will break the water into hydrogen gas.
01:30
And oxygen gas.
01:33
We don't have h2o anymore.
01:36
We have hydrogen and oxygen.
01:38
Two things with very different formulas and very different properties.
01:43
So that would be a chemical change.
01:45
So we are ready to tackle question here.
01:49
So let's look at letter a.
01:52
Letter a says we are cutting up food.
01:57
So think about food that you cut up.
01:59
You have a tomato.
02:00
You cut it up.
02:01
It's still tomato.
02:02
It's just in smaller pieces, but it's still the same substance.
02:06
So cutting food, chopping wood, cutting up paper, all of those are physical changes.
02:16
Letter b, we have food interacting with saliva and digestive enzymes.
02:25
So that food is chemically being broken down into simpler substances...
