Chemical & Physical Reactions

Question 1

What is a chemical reaction?

Answer 1

When a chemical reaction takes place, one or two new substances are made.

A chemical reaction CANNOT be reversed

Question 2

Name 5 points from which we know a chemical reaction is taking place

Answer 2

• A change in colour
• Bubbles that show us a gas is being made
• A change in mass as a gas escapes
• Light energy being given out
• A change in temperature

Question 3

What is a physical change?

Answer 3

Something that CANNOT create a new substance.

Something that CAN be reversed

Question 4

Examples of CR and PC…

Answer 4

PC:
Boiling the kettle
Alcohol evaporating
Freezing yoghurt

CR:
Making toast
Frying an egg
Neutralising an acid

Question 5

Why is neutralising an acid not a physical change?

Answer 5

Because you have 2 reactants that create a new product

Question 6

Testing for Hydrogen is also called the…

Answer 6

Squeaky pop test

Question 7

What gas is produced in the Squeaky Pop Test?

Answer 7

Hydrogen

Question 8

Hydrogen is lighter than air. What proof of this have you seen in this experiment?

Answer 8

The pop was at the top of the test tube as this is where most of the gas was as the hydrogen went up meaning it was lighter than air.

Question 9

Is hydrogen gas flammable

Answer 9

Yes

Question 10

Do metals always make hydrogen gas when reacting with acids?

Answer 10

No, Copper for example doesn’t react with acids because it’s lower down on the reaction table.

Question 11

What is the test called when magnesium reacted with hydrochloric acid?

Answer 11

The Squeaky pop test

Question 12

What is the test for Carbon dioxide?

Answer 12

Putting gas through limewater.

Positive result: limewater turns milky and cloudy

Question 13

What is the test for hydrogen?

Answer 13

Hold a lit splint in the gas

Positive result! Burns with a squeaky pop

Question 14

What is the test for oxygen?

Answer 14

Hold a glowing splint in the gas

Positive result: Relights splint

Question 15

Metal + acid

Answer 15

Salt + hydrogen

Question 16

Carbonate + acid

Answer 16

Salt + water + Carbon Dioxide

Question 17

In air - Carbon

Answer 17

Orange flame

Question 18

In air - Sulphur

Answer 18

Blue, small flame

Question 19

In air - zinc

Answer 19

Blue silver

Question 20

In air - calcium

Answer 20

Orange flame - rocks go white

Question 21

in air - Iron

Answer 21

Orange/ gold like a sparkler

Question 22

in air - Magnesium

Answer 22

Bright white flame

Question 23

Test for water

Answer 23

Putting cobalt chloride paper into water

Positive result: turns pink

Question 24

Independent

Answer 24

The variable that you change

Question 25

Control

Answer 25

The variable you keep the same

Question 26

Dependent

Answer 26

The variable that you measure

Question 27

The fire triangle

Answer 27

Oxygen, fuel, heat

All 3 are needed

Question 28

Product of burning

Answer 28

Carbon dioxide - Co2

Question 29

Differences in PC and CR

Answer 29

CR’s cannot be reversed - PC’s can

CR’s create a new chemical substance - PC’s can’t

Question 30

What is complete combustion?

Answer 30

When there is enough oxygen for the fuel to combust fully

Question 31

What is incomplete combustion?

Answer 31

When there is not enough oxygen so the fuel can not burn fully

Question 32

What is the difference between complete and incomplete combustion?

Answer 32

Complete combustion has enough oxygen to burn foully unlike incomplete combustion.
They create different products
Complete combustion creates carbon dioxide
Incomplete combustion creates carbon monoxide (a toxic gas)

Question 33

How can monoxide be dangerous?

Answer 33

When breathed it displaces oxygen in the blood

It’s invisible and you can’t smell it

Question 34

What are the similarities of incomplete and complete combustion?

Answer 34

A chemical reaction is still occurring between fuel and oxygen to produce heat and light

Question 35

What is a word equation?

Answer 35

Describing a chemical reaction with words.

For example 2 reactants changing into a product.

Question 36

Metal + oxygen

Answer 36

Metal oxide

Question 37

Element + oxygen

Answer 37

Element dioxide