Chemistry

Question 1

Melting point

Answer 1

The melting point of a substance is the temperature at which it changes from a solid to a liquid (melts).
To identify an unknown substance, the melting point of the substance can be determined and compared to the melting points of known substances.
It is a characteristic property because no two pure substances have the same melting point.

Question 2

Characteristic property

Answer 2

It is a characteristic property because no two pure substances have the same property.

Answer 3

The boiling point of a substance is the temperature at which it changes from a liquid to a gas (boils/evaporates).
It is a characteristic property because no two pure substances have the same boiling point.
The boiling point of an unknown substance can be determined and compared to the boiling points of known substances.

Question 4

Density

Answer 4

Density is the ratio (relationship/proportion) between the mass and volume of a substance.

Density is a characteristic property.

The unit used to express density is g/mL or g/cm3 (note: 1 mL = 1 cm3).

Question 5

A = 1KG
B = 5KG
AREAS ARE THE SAME

Answer 5

B has a higher density than A, because B has a higher mass for the same amount of space occupied.

Question 6

A = 10KG
B = 10 KG
B AREA IS BIGGER

Answer 6

A has a higher density than B, because for the same amount of mass A occupies less space.

Question 7

A) M = 20KG, V= 1L
B) M = 40KG, V = 2L

Answer 7

A has a higher density than B, because for the same amount of mass A occupies less space.

Question 8

Density formula

Answer 8

D = M/V
D = g/ml or g/cm3

Question 9

Mass formula

Answer 9

M = D x V
Mass (g)

Question 10

Volume

Answer 10

V = M/D
V = ml or cm3

Question 11

Concentration

Answer 11

The concentration of a solution is the quantity of dissolved solute in a quantity of solution.

Question 12

Formula CONCENTRATION

Answer 12

C = M/V
M = C x V
V = C/M

Question 13

Solubility

Answer 13

Definition: a measure of the maximum amount of solute that can be dissolved in a solvent at a given temperature
It is a characteristic property because no two pure substances share the same solubility for a given temperature.

Question 14

Saturation/Unsaturation

Answer 14

The solubility of a substance can be determined by slowly dissolving the solute into a solvent until the solute will no longer dissolve.
The saturation level describes how much solute is dissolved in the solvent.
An unsaturated solution has less solute dissolved in it than the maximum amount.
A saturated solution has exactly the maximum amount of solute that can be dissolved, similar to its solubility value. This means if more solute is added, it will not dissolve.

Question 15

Solid : effect of temperature on solubility

Answer 15

As the temperature increases, the solubility will also increase
To dissolve more solid, heat up the solution

Question 16

Gas: effect of temperature on solubility

Answer 16

As the temperature increases, the solubility will decrease
To dissolve more gas, cool down the solution

Question 17

SOLUBILITY CURVES

Answer 17

The solubility of a substance compared to the temperature of the solution can be represented as a graph.

Question 18

Indicators

Answer 18

Indicators are substances that change colour, because of a chemical change, when in the presence or absence of a chemical species such as an acid or a base.

Question 19

Blue and red litmus paper

Answer 19

Acid; base or neutral substance
Red = acid
Blue = base
Red stays red + blue stays blue = neutral

Question 20

pH paper

Answer 20

Specific pH of a substance
Paper turns a different colour and you compare it to a colour chart to find out the pH

Question 21

Cobalt chloride paper

Answer 21

Water
The paper changes colour in the presence of water
The paper stays blue when there is no water present

Question 22

Iodine

Answer 22

Starch
Starch turns blue in the presence of iodine

Question 23

Limewater test

Answer 23

Carbon dioxide
If the clear, colourless limewater turns milky white, CO2 is present

Question 24

Solutions

Answer 24

A solution consists of a solute dissolved in a solvent.
In an aqueous solution, the solvent is water.
The solute is the substance that is dissolved in the water.

Question 25

Seawater solute

Answer 25

Sodium chloride, magnesium, sulphate

Question 26

Urine solute

Answer 26

Urea, uric acid, sodium, potassium

Question 27

Juice

Answer 27

sugar, flavour

Question 28

Plasma

Answer 28

Salts, sugars, proteins

Question 29

Homogeneous vs heterogenous mixture

Question 30

universal solvent

Answer 30

WATER

Question 31

CHEMICAL
PROPERTIES

Answer 31

Properties that can be observed or measured when a substance undergoes a chemical change.
A chemical reaction needs to be conducted to show the property.
Can be used to predict how substances react.
Can include compressibility, radioactivity, toxicity, flammability, heat of combustion, reactivity between chemicals, etc.

Question 32

PHYSICAL PROPERTIES

Answer 32

Properties that can be observed without bringing a chemical change.
No chemical reaction is needed here.
Mostly used in identifying or describing the substance.
Can include molecular weight, boiling point, melting point, freezing point, volume, mass, length, density texture, colour, odour, shape, solubility, etc.