energy changes

Question 1

what is a redox reaction?

Answer 1

a reaction where both oxidation and reduction occur

Question 2

what is a endothermic reaction?

Answer 2

where energy is taken in from the surroundings (temperature decreases)

Question 3

what is a exothermic reaction?

Answer 3

when energy is released from its surroundings. (temperature increases)

Question 4

where does metallic bonding occur?

Answer 4

in metallic elements and alloys

Question 5

what is covalent bonding

Answer 5

the particles are atoms which share pairs of electrons

Question 6

where does ionic bonding occur?

Answer 6

in compounds formed from metals combined with non metals

Question 7

where does covalent bonding occur?

Answer 7

in non metallic elements and compounds of non metals

Question 8

what is metallic bonding?

Answer 8

the particles are atoms which share delocalised electrons

Question 9

what is ionic bonding?

Answer 9

particles are oppositely charged ions

Question 10

what is atomic structure?

Answer 10

atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in shells

Question 11

name three types of strong chemical bonds-

Answer 11

ionic, covalent and metallic

Question 12

define relative atomic mass and relative formula mass-

Answer 12

Relative atomic mass- average mass of atoms in an element taking into account masses and abundance of its isotopes
Relative formula mass- sum of relative atomic masses of all atoms in the formula

Question 13

oxidation/reduction defined in terms of electron transfer-

Answer 13

oxidation - loss of electrons
reduction- gain of electrons

Question 14

what is oxidation/reduction?

Answer 14

oxidation- when a substance gains oxygen
reduction- when a substance loses oxygen

Question 15

how are metals more reactive than carbon extracted?

Answer 15

by electrolysis

Question 16

1) what is general equation for a reaction between metals and acids?
2) what type of reaction is this?

Answer 16

1) metal + acid —> salt + hydrogen
2) redox reaction

Question 17

example of exothermic reaction-

Answer 17

(acid + alkali)

Question 18

example of endothermic reaction-

Answer 18

(citric acid + sodium hydrogen carbonate)

Question 19

what is activation energy?

Answer 19

minimum amount of energy that particles need to react

Question 20

bond breaking -

Answer 20

endothermic- energy must be supplied to break existing bonds

Question 21

bond forming -

Answer 21

exothermic - energy is released when new bonds are formed

Question 22

what happens during a chemical reaction?

Answer 22

during a chemical reaction old bonds are broken and new bonds are formed

Question 23

how to calculate bond energies-

Answer 23

1) find energy required to break original bonds
2) find energy released by forming new bonds
3) find overall change for reaction

Question 24

what is a fuel cell? -

Answer 24

an electrical cell that’s supplied with fuel and oxygen