Unit 2, Physical and Chemical Changes

Question 1

What is a physical change?

Answer 1

A change that happens without changing the identity of a substance.

Question 1

What are some examples of physical changes?

Answer 1

-changes in shape
-smashing a glass
-boiling water
-dissolving sugar
-tearing paper
-chopping wood
-letting a soda go flat

Question 2

What is a chemical change?

Answer 2

A change that happens that changes the identity of a substance.

Question 3

What is evidence of a chemical change?

Answer 3

-new color
-bubbles form
-precipitate formed
-temperature change(energy change)
-light is made(energy change)
-sound is given off(energy change)

Question 4

What are some examples of a chemical change?

Answer 4

-rusting
-rotting
-explosion
-fire
-bubbles when something is dropped in acid
-activating ice pack
-a cut healing

Question 5

What two physical properties do rubber and wood have in common?

Answer 5

1. don’t conduct electricity
2. not attracted to a magnet

Question 6

solid - gas

Answer 6

sublimation

Question 7

gas - solid

Answer 7

deposition

Question 8

solid - liquid

Answer 8

melting

Question 9

liquid - gas

Answer 9

boiling, evaporating

Question 9

liquid - solid

Answer 9

freezing

Question 10

gas - liquid

Answer 10

condensation

Question 11

What is 100*C called

Answer 11

“boiling point” and “condensation point”

Question 12

What is 0*C called

Answer 12

“freezing point” and “melting point”

Question 13

If a block of ice is melted into a puddle of water, would that be a chemical or physical change?

Answer 13

Physical as changes in phase of matter are not changing the identity of the substance

Question 14

When you eat a McDonalds 30 piece chicken McNugget meal combo for energy, would that be a physical or chemical change?

Answer 14

Chemical as the food is dissolved in your stomach acid and it is an irreversible change.

Question 15

What is a mixture?

Answer 15

It is a substance made up of two or more pure substances not chemically bonded

Question 16

Is sugar a mixture or compound?

Answer 16

compound as it is made up of 2 or more types of atoms bonded chemically

Question 17

Is a fruit salad a mixture or compound?

Answer 17

mixture

Question 18

If you dissolve sugar in water, how would you get the sugar back?

Answer 18

You could let the water sit and evaporate and the sugar will be left in the container

Question 19

When water is boiled, are the bubbles formed made out of hydrogen gas, oxygen gas, both, or neither?

Answer 19

Neither, as boiling is a physical change so, it can’t separate the water molecules into just hydrogen and just oxygen

Question 20

During the electrolysis lab, you separated the water molecules into hydrogen and oxygen gas, is this a chemical or physical change?

Answer 20

Chemical as it created bubbles, and it changed the identity of the substance, in this case from water to hydrogen and oxygen

Question 21

How did we determine the ratio of gasses during the electrolysis lab?

Answer 21

Water’s chemical formula is H2O, so there is 2x more hydrogen than oxygen. The slope compares the air between the gases from the two wires. The slope was 2 black/red. Slope is equivalent to ratios so the ratio is 2:1.