Lecture 1-Elements,compounds & mixtures

Question 1

What is a molecule?

Answer 1

A group of 2/+ atoms that are joined together

Question 2

How can elements exist?

Answer 2

As atoms/molecules

Question 3

What are compounds made of?

Answer 3

Molecules

Question 4

How do chemical reactions change the identity of compounds?

Answer 4

Rearranging the atoms to change the ratios of chemical combinations

Question 5

What is combing power/valency?

Answer 5

The ability of an atom of one element to combine with other atoms based on the n.o of e- an atom will give/take to form a chemical bond

Question 6

What determines the atom’s chemical + electrical properties?

Answer 6

E- in the outermost orbitals

Question 7

What is the RAM equation?

Answer 7

Mass of 1 atom of element
——————————————–
1/12 mass of 1 atom of carbon-12

Question 8

What is the RMM equation?

Answer 8

Mass of 1 molecule of substance
————————————————
1/12 mass of 1 atom of carbon-12

Question 9

What are the qualities of intensive properties?

Answer 9

• Doesn’t depend on the amount of matter

- Identify substances

Question 10

Examples of intensive properties?

Answer 10

Density, Colour, Boiling point

Question 11

Examples of extensive properties?

Answer 11

Mass, Volume, Weight

Question 12

What do physical properties examine and why?

Answer 12

A sample of pure substance

-because of molecular structure + strength of intermolecular forces

Question 13

How are chemical properties observed and why?

Answer 13

During a chemical reaction

-because of the distribution of e- (around the atom’s nucleus)

Question 14

A physical change is a change in …..?

Answer 14

energy

Question 15

A chemical change is a change in……..?

Answer 15

identity

Question 16

How do you separate mixtures?

Answer 16

By using differences in physical properties

Question 17

Basic separation techniques?

Answer 17

Filtration
Crystallization
Extraction
Distillation
Magnetisation
Chromatography

Question 18

What is density?

Answer 18

Mass to volume ratio

Question 19

Can pure substances be separated by physical means?

Answer 19

NO

Question 20

What is an element?

Answer 20

The simplest from of matter that has a unique set of properties

Question 21

What is a compound?

Answer 21

A substance that contains 2/+ elements chemically combined in a fixed proportion

Question 22

What is a heterogeneous mixture and give an example?

Answer 22

MULTIPLE PHASE

• Various properties
• non-uniform appearance
  e. g. emulsion / colloid

Question 23

Describe a distinctive property of pure substances?

Answer 23

Can only change in identity + properties chemically