Year 8 Semester 2 Revision

Question 1

Chemical Properties

Answer 1

It is a type of substance that you can see/observe that does not change the chemical matter or has the same matter.
Eg Some examples of chemical properties are vapor, energy level, electric charge and toxicity.

Question 2

Physical Properties

Answer 2

It is a matter that can be observed and measured without changing the physical matter.
Eg Some examples of physical properties are the smell, taste, touch, hearing, the appearance, colour, texture, odor and the weight of the substance/matter/objects.

Question 3

Chemical Reaction

Answer 3

It is when a substance chemical changes from one or more chemicals are produce or made.

Question 4

Reactants

Answer 4

It is when a substance takes part or undergoes through a chemical change.

Question 5

Products

Answer 5

It is the new chemical substance that came or resulted from a chemical reaction.

Question 6

Precipitate

Answer 6

It is a solid substance or product that came or resulted from a chemical reaction which can not dissolve in water.

Question 7

Reaction Rate

Answer 7

The speed of the reaction occurred or took place.

Question 8

Catalyst

Answer 8

It is the chemical that helps it start or speed up a chemical reaction but is still stayed there once the reaction has finished.

Question 9

Rusting

Answer 9

It is the corrosion of the iron and it turns to a reddish orange colour.

Question 10

Corrosion

Answer 10

It is a chemical reaction that wears away metal by exposing the metal to oxygen and water.

Question 11

Rust

Answer 11

It is a reddish orange colour that is formed when a metal is exposed to oxygen and water.

Question 12

Surface protection

Answer 12

It is the coating of metal to prevent or stop corrosion occurring on metals.

Question 13

Galvanising

Answer 13

It is when you are protecting metal by covering it with more reactive metal that will corrode first and protect the other metal.

Question 14

Burning

Answer 14

It is a combination of substance with oxygen to form a flame.

Question 15

Oxidation

Answer 15

It was a chemical reaction which involving the loss of electrons by a substance

Question 16

Fossil fuel

Answer 16

It is substances such as oil and coal which is produce from the remains of ancient organisms.

Question 17

Combustion

Answer 17

It is the process of combining oxygen, most commonly burning with a flame.

Question 18

What is digestion?

Answer 18

Digestion involves the breaking down of food so that the nutrients it contains can be absorbed into your blood and carried to each cell in your body.

Question 19

What are the five key processes in supplying nutrients to cells?

Answer 19

1. ingestion
2. mechanical digestion
3. chemical digestion
4. absorption of the broken-down food into your cells 5. assimilation

Question 20

What do teeth do?

Answer 20

Bite and chew food to break it down to smaller pieces.

Question 21

What does saliva do?

Answer 21

Secretes enzymes from the saliva glands which begins the chemical digestion of some carbohydrates.

Question 22

List the order of the organs in the digestive systems, in terms of when you first put food into the body to when waste comes out.

Answer 22

Mouth 
Oesophagus 
Stomach
 Small Intestine
Large Intestine 
Anus

Question 23

Peristalsis

Answer 23

Is the process of pushing food along the oesophagus or small intestine by the action of muscles

Question 24

Villi are

Answer 24

Tiny finger-like projections from the wall of the intestine that maximize the surface area of the structure to increase the efficiency of nutrient absorption.

Question 25

Enzymes are

Answer 25

Special chemicals that speed up reactions but are themselves not used up in the reaction

Question 26

Proteases are

Answer 26

Enzymes that break proteins down into amino acids

Question 27

What is the difference between mechanical and chemical digestion?

Answer 27

Mechanical - digestion that uses physical factors such as chewing with the teeth Chemical - the chemical reactions changing food into simpler substances that are absorbed into the bloodstream for use in other parts of the body