Chemical Changes, Physical Changes, and Mixtures

Question 1

What is a chemical change?

Answer 1

a change where the chemical composition of a substance is altered.
For example C3H8 + 5O2 —> 3CO2 + 4H2O

Question 2

Is water boiling a chemical change?

Answer 2

NOOOOOOOO!!!! Its always H20. Physical change but not chemical.

Question 3

Is propane burning a chemical change?

Answer 3

YES! When it comes together with oxygen, it becomes something new. First Propane, then turns into CO2 Carbon dioxide.

Question 4

What’s something important to remember with chemical changes?

Answer 4

Matter cannot be created or destroyed (law of conservation). One side has to be on the other side, but it can be bonded to something different.
What the numbers represent - 3CO2 Three Carbon atoms and O2 two oxygen atoms
soo… 5O2 = 10 oxygen atoms is going into this reaction.

Question 5

What is a catalyst in a chemical reaction?

Answer 5

Something that starts a chemical reaction, such as a spark. The fire as a RESULT. Often, Fire is in chemical reactions (why you use Bunsen burners).

Question 6

What is a mixture? What are the two types of mixtures?

Answer 6

a material that can be separated by physical means into two or more substances.

Two Types-

1. Solution
2. suspension

Question 7

What is a solution?

Answer 7

It is a homogeneous (even throughout) mixture in which one substance has dissolved into the other(s).
ex: salt water- how it blends together after it is hot.

Question 8

What is a suspension?

Answer 8

a system in which small particles are kept dispersed by agitation or molecular motion in the surrounding medium
ex: muddy water, it separates, mud at the bottom, water at the top.

So if you come back after a couple hours, a solution would still be mixed together (saltwater) and a suspension would be seperated (muddy water)

Question 9

What is a physical change?

Answer 9

A change from one state to another WITHOUT a change in chemical composition.

Question 10

What are three basic states of matter?

Answer 10

-solid
-liquid
-gas
(each are defined by certain qualities)

Question 11

Defining qualities of a solid..

Answer 11

• cannot be compressed

- does not take shape of container

Question 12

Defining qualities of a liquid..

Answer 12

• cannot be compressed

- DOES take shape of container

Question 13

Gas

Answer 13

• can be compressed

- does take shape of container

Question 14

Two reasons why physical change occurs..

Answer 14

1. temperature change

2. pressure

Question 15

What temperature forms are the three states of matter?

Answer 15

• Solid is in its coldest state
• liquid is middle state
• gas is hottest state

*Every substance has its own unique boiling point and freezing point.

Question 16

What are the two factors that cause a substance to change state?

Answer 16

1. Temperature

2. Pressure

Question 17

What is water’s-

- boiling point
- freezing point
	- what happens when you change the altitude?

Answer 17

-water boils at 212 degrees f’ at sea level
-water freezes at 32 degrees f’ at sea level
BUT its not true if you change altitude because of PRESSURE
(less atmosphere pushing down, less pressure)

Question 18

What happens if there is more pressure (in the atmosphere)? less pressure? what is pressure trying to do?

Answer 18

With more pressure, the more (the atmosphere) was to be solid
less pressure, the more it wants to be gas

Higher pressure= higher temperature because molecules are moving faster

Question 19

What are the two gas laws?

Answer 19

1. Charles’ law (Temperature increases = then volume increases)
   ex: boiling water with a lid, you hear it rattling around. because its taking up more space and expanding.
2. Boyle’s Law (as pressure increases= volume decreases)
   ex: swimming at the bottom the pool with a balloon, it compresses the air because of pressure.

Question 20

What is pH?

Answer 20

pH is a measure of the presence of hydrogen ions in a substance. It affects its property to bond with other substances.
-gives it a sort of a charge, ionic.

acids versus alkaline or bases on the other sides.
High pH=basic/alkaline
Low pH= acidic

Question 21

How do you measure pH?

Answer 21

with a litmus test.

Question 22

If something burns, what kind of pH is it?

Answer 22

It can be either acidic or basic. DON’T be fooled by thinking that the Acid in something that would be something that BURNS through something else or caustic. Bases can be as well. Bleach is a base.

Question 23

What is in the middle of the pH scale?

Answer 23

distilled water.

Question 24

What are acids?

What are alkaline (bases)?

Answer 24

acids- milk, coffee, beer, stronger acids, vinegar, gastric acid, battery acid, citric acids (lots of foods are acid)

alkaline- hand soap, bleach, lye, ammonia (lots of cleaners)
High pH=basic/alkaline
Low pH= acidic

Question 25

What is alkaline?

Answer 25

base