chem Apr 18 (🎉🎂💀)

Question 1

What is a chemical reaction?

Answer 1

A change in which atoms are rearranged to create new substances

Question 2

what happens in a chemical reaction?

Answer 2

atoms are rearranged

Question 3

All chemical reactions

Answer 3

Make new substances

Transfer energy to or from surroundings.
Are not easily reversible
Have reactants and products that have the same mass

Question 4

indicators that a chemical reaction is happening

Answer 4

Visible flames/sparks
Change in smell
Change in colour
Change in temperature
Loud bang/effervescence

Question 5

Uses of chemical reactions

Answer 5

Creation of medicines
Production of fabrics
Cement
Combustion of fossil fuels for power

Question 6

Useless chemical reactions

Answer 6

rusting (oxidation)
food rotting

Question 7

In a physical change…

Answer 7

Change of state and dissolving are reversible

Question 8

what is a fuel?

Answer 8

a material that burns to transfer energy by heating

Question 9

examples of fuels

Answer 9

wood, coal, biogas, LPG, petrol, diesel

Question 10

what are fossil fuels

Answer 10

fuels that are made from the remains of animals and plants that died millions of years ago,

Question 11

examples of fossil fuels

Answer 11

coal, oil and natural gas

Question 12

what are oxidation reactions?

Answer 12

In oxidation reactions substances join with oxygen to form oxides

Question 13

examples of oxidation reactions

Answer 13

rusting and combustion

Question 14

what is combustion

Answer 14

A chemical reaction in which a substance reacts quickly with oxygen and gives out light and heat.

Question 15

examples of combustion reaction

Answer 15

Methane+Oxygen–> Carbon dioxide + water
glucose+oxygen–> Carbon dioxide+water
Magnesium+ Oxygen–> Magnesium oxide

Question 16

what is decomposition?

Answer 16

A chemical reaction in which a compound breaks down to form simpler compounds and/or elements (usually with heat (thermal decomposition)).

Question 17

Difference between decomposition and combustion

Answer 17

A decomposition reaction produces multiple products from a single reactant. On the other hand a combustion reaction is a reaction between a substance and oxygen to make oxides.

Question 18

examples of decomposition reactions

Answer 18

Hydrogen peroxide (H2O2)–> water+oxygen
Copper carbonate–> Copper oxide+Carbon dioxide

Question 19

what is the law of conservation of mass

Answer 19

law that states that the mass of the reactants MUST be the same as that of the products.

In a chemical reaction, mass is neither created nor destroyed.

Question 20

example of law of conservation of mass in action

Answer 20

Copper oxide + carbon dioxide–> Copper Carbonate
(87g) (50g) (137g)

Question 21

Endothermic change

Answer 21

energy from the surroundings ENters the system (chemical reaction)

Question 22

Exothermic change

Answer 22

energy from the chemical reaction EXits and is transferred to the surroundings

Question 23

examples of endothermic processes

Answer 23

melting ice cubes- takes in energy from surroundings to melt

melting, boiling, and evaporation- takes in energy to melt, boiling takes in energy so that water becomes gas same for evap

sweating- liquid from skin evaporates :))

Question 24

example of exothermic processes

Answer 24

combustion- energy exits the reaction

freezing water- requires the release of energy for liquid to become solid

rusting- generates lots of heat

respiration

Question 25

On which side of a word equation do the reactants go?

Answer 25

On the left

Question 26

What are the products formed when a carbon based fuel undergoes combustion?

Answer 26

CO2 + H2O (Carbon dioxide and water)

Question 27

What does thermal decomposition mean?

Answer 27

The breaking down of substances by using heat

Question 28

What is produced when magnesium carbonate undergoes thermal decomposition?

Answer 28

Magnesium oxide and carbon dioxide (no water cuz no hydrogen 😒)

Question 29

Why in a chemical reaction can it sometimes appear that the mass is not being conserved?

Answer 29

A gas could be produced which means that the mass it accounts for will escape

Question 30

What is a physical change?

Answer 30

One where the physical properties of a substance changes, but a new substance is not formed. Particles may move or be arranged differently

Question 31

What is meant by a reversible reaction?

Answer 31

A reaction in which the you can get back to the substances you started with (physical)

Question 32

examples of physical change

Answer 32

Melting an ice cube. Boiling water. Mixing sand and water. Breaking a glass. Dissolving sugar and water.

Question 33

physical changes can/cannot be exothermic/endothermic

Answer 33

can

Question 34

examples of chemical change

Answer 34

combustion respiration photosynthesis

Question 35

Is ice melting a physical or a chemical change?

Answer 35

Physical

Question 36

In which type of reaction will energy be transferred to the surroundings?

Answer 36

Exothermic

Question 37

In which type of reactions will energy escape the surroundings and enter the system

Answer 37

Endothermic

Question 38

What will happen to the temperature in an endothermic reaction?

Answer 38

It decreases

Question 39

the temperature of the surroundings/system is measured

Answer 39

SURROUNDINGS🤬

Question 40

What will happen to the temperature in an exothermic reaction?

Answer 40

it increases

Question 41

Why is an instant ice pack an example of an endothermic reaction?

Answer 41

As it takes in energy from the surroundings and decreases the temperature of the surroundings

Question 42

Does making bonds require or release energy?

Answer 42

RELEASES to minimize the repulsion between the atoms.

Question 43

If more energy is needed for breaking bonds that is released from making bonds, which type of reaction will this be?

Answer 43

ENDOTHERMIC

Question 44

If less energy is needed for breaking bonds than is released from making bonds, which type of reaction will this be?

Answer 44

EXOTHERMIC

Question 45

What is a catalyst?

Answer 45

A chemical which speeds up the reaction and lowers the energy needed for a reaction