3.1 INTRO, ELEMENTS, COMPOUNDS, SOLUTIONS

Question 1

what is a physical change?

Answer 1

• creates no new substances
• usually easy to reverse
• absorb or release small amounts of energy

Question 2

what is a chemical change?

Answer 2

• create new substances
• usually difficult to reverse
• absorb or release large amounts of energy

Question 3

chemical test for water:

Answer 3

• anhydrous copper (II) sulphate
• turns from white to blue

Question 4

physical test for water:

Answer 4

• melting point is 0 degrees
• boiling point is 100 degrees
• pure water is closest to these values

Question 5

definition of an element:

Answer 5

a substance containing only one type of atom

Question 6

definition of a compound:

Answer 6

a substance containing more than one type of atom, chemically bonded together

Question 7

what is a molecule?

Answer 7

two or more atoms chemically bonded together

Question 8

definition of a mixture:

Answer 8

contains two or more substances not chemically bonded together

Question 9

properties of metal elements:

Answer 9

• high MP/BP
• electrical conductors
• malleable
• shiny

Question 10

properties of non- metal elements:

Answer 10

• low MP/BP
• electrical insulators
• brittle
• dull

Question 11

where are metal elements?

Answer 11

left hand side of the staircase

Question 12

what are the 8 diatomic molecules?

Answer 12

• hydrogen
• nitrogen
• oxygen
• fluorine
• chlorine
• bromine
• iodine
• astatine

Question 13

where are diatomic molecules on the periodic table?

Answer 13

upside down L, 1 row from the end

Question 14

how can you make a compound?

Answer 14

heating their elements together

Question 15

properties of compounds:

Answer 15

usually totally different from the properties of the elements the compound is made from

Question 16

why do we make the compound ammonium chloride in a tube?

Answer 16

to illustrate diffusion of gases

Question 17

ammonium chloride in a tube method:

Answer 17

• two gases ammonia + hydrogen chloride diffuse from the ends of the sealed tube
• where they meet ammonium chloride forms as a white smoke
• ammonia + hydrogen chloride —> ammonium chloride
• this shows that the hydrogen chloride molecules must be heavier, as they diffused slower

Question 18

definition of a solute:

Answer 18

the substance which is going to be dissolved

Question 19

definition of a solvent:

Answer 19

the liquid which is going to be the dissolvent

Question 20

definition of a solution:

Answer 20

the resulting mixture of solute dissolved in solvent

Question 21

definition of a saturated:

Answer 21

a solution in which no more solute can be dissolved

Question 22

definition of a suspension:

Answer 22

a solid floating in a liquid because it cannot dissolve

Question 23

definition of a soluble:

Answer 23

a substance which can be dissolved

Question 24

definition of insoluble:

Answer 24

a substance which cannot be dissolved

Question 25

P2 how do we measure solubility?

Answer 25

in g per 100g of solvent
for example, the solubility of sodium chloride in water is 36.37g/ 100g, this means that up to 36.37g of sodium chloride can dissolve into 100g of water

Question 26

P2 what does solubility vary with?

Answer 26

temperature

Question 27

P2 what does the line show on a solubility curve?

Answer 27

shows the maximum mass of solid which can be dissolved at each temperature

Question 28

P2 what does above the line show on a solubility curve?

Answer 28

• insoluble
• more than the maximum mass of solid, so some will dissolve and some won’t

Question 29

P2 what does below the line show on a solubility curve?

Answer 29

• soluble
• less than the maximum mass of solid, so it will all dissolve