CHEM TEST 2

Question 1

what is a physical change

Answer 1

a change that does not create a new substance. e.g ice to water

Question 2

what is a chemical change

Answer 2

when a new substance with a diffrent formula is created. e.g burning anything

Question 3

what does (aq) mean

Answer 3

aqueous meaning dissloved in water

Question 4

what is the diffrence between an exothermic and endothermic reaction

Answer 4

Exothermic means that it produces heat, endothermic means that it sucks in heat

Question 5

what is combustion and its general form

Answer 5

combustion is any reaction where a substance burns in oxygen to produce light and heat.
fuel+oxygen - carbon dioxide+water

Question 6

respiration , and its general form

Answer 6

a chemical reaction that goes into cells of all living things
glucose+oxygen gas - carbon dioxide+water

Question 7

corrosion, general form

Answer 7

When metals combine with oxygen gas in the air to from metal oxides
metal+oxygen gas - metal oxide

Question 8

decomposition, general form

Answer 8

when a single reactant breaks apart to form several products
XY - X+Y

Question 9

combination, general form

Answer 9

when to reactants combine to form a single product
X+Y - XY

Question 10

percipitation, general form

Answer 10

when 2 clear sloutions are mixed together they react to form an insoluable solid
salt (aq) + salt (aq) - solid+ salt (aq)

Question 11

neutralisation, general form

Answer 11

when an acid reacts with a base
acid+base - salt + water

Question 12

acid and metal, general form

Answer 12

when acids react with metals
acid+metal - salt+hydrogen gas
MASH

Question 13

acid & carbonate, general form

Answer 13

when acids react with carbonates
acid+carbonate - salt+water+carbon dioxide
CWA

Question 14

define solid, what happens when temp is increased

Answer 14

particles are close together vibrating. as temp increases particle speed and energy increases until melting point is reached and the bonds break to form a liquid

Question 15

define liquid, what happens when temp is increased

Answer 15

particels that are close togther but moving over each other. as temp increases so does spped and energy until bonds break and a gas is formed

Question 16

define gas, what happens when temp is increased

Answer 16

particles are individual and far apart moving rapidly in all directions. as temp increases speed/energy increases

Question 17

how do you calculate reaction rate

Answer 17

change in product
time

change in reactants
time

Question 18

what are the two conditions of collison theory

Answer 18

1. energy of the collision must be big enough to break bonds
2. bonds must have the correct orientation

Question 19

how does temp affect reaction rate , draw diagram

Answer 19

low temp: the particles move too slowly with low energy. this results in most collisions being unsuccessful
high temp:th eparticel sar emoving faster with more energy. this results in more succsessful collisions ( but not all due to wrong orientations)

Question 20

how does concentration affect reaction rate, draw

Answer 20

low concentration: a low number of successful collision as it is unlikley that the particles will collide. this means a low reactino rate
high concentration: lots more successful collisions ( same % of successful collisions as low concentration). this means faster reaction rate

Question 21

how does a successful collision occour

Answer 21

when particels have enough energy and the correct orientation.

Question 22

how does surface area affect reaction rate, draw

Answer 22

low surface are: means less area for a solution to react with, low number of particles on the outside of a solid or liquid so low number of collisions and successful collisions. this means low reaction rate
high surface area: more surface area is exposed so more collisions can occour. still the same % of successful collisions as low surface area. this means faster reaction rate

Question 23

what is the law of conservation of mass

Answer 23

matter cannot be created or destroyed but it can change form