Chemistry :(

Question 1

Define the law of conservation of matter.

Answer 1

Matter can be neither created nor destroyed. The atoms are simply just rearranged to create new substances.

Question 2

Define endothermic.

Answer 2

A reaction that absorbs heat, taking it from the surroundings and making it feel colder. The products have more energy than the reactants.

Question 3

Define exothermic.

Answer 3

A reaction that releases energy. The reactants have more energy than the products.

Question 4

Is photosynthesis endo or exothermic?

Answer 4

Endothermic.

Question 5

Is respiration endo or exothermic?

Answer 5

Exothermic.

Question 6

Define combustion.

Answer 6

Types of exothermic reactions that require a fuel and an oxygen.

Question 7

Define complete combustion and provide an example.

Answer 7

A type of combustion that occurs only if sufficient oxygen is present, the products always being carbon dioxide and water. e.g. octane + oxygen gas -> carbon dioxide + water.

Question 8

Define an incomplete combustion and provide an example.

Answer 8

A type of combustion that occurs when insufficient oxygen is present, the products always being carbon monoxide/water, and carbon. e.g. methane + oxygen gas -> water + carbon

Question 9

What is the general equation of combustion?

Answer 9

fuel + oxygen gas -> carbon dioxide + water + energy

Question 10

Define a corrosion reaction.

Answer 10

A type of reaction that requires oxygen and involves metals corroding

Question 11

Define acids

Answer 11

substances that release hydrogen ions (H+) into aqueous solutions (e.g. hydrochloric acid in your stomach)

Question 12

Define bases.

Answer 12

substances that release hydroxide ions (OH+). E.g. ammonia

Question 13

What are the 6 properties of acids?

Answer 13

• corrosive
• turns blue litmus paper red
• have a sour taste
• conduct electricity
• are neautralised by bases
• react with some metals, releasing hydrogen gas and leaving salt behind.

Question 14

What are the 6 properties of bases?

Answer 14

• caustic
• have a soapy, slimy feel
• have a bitter taste
• conduct electricity
• Turn red litmus paper blue
• are neutralised by acids, producing water and salt.

Question 15

Define alkalis.

Answer 15

Bases that are soluble in water.

Question 16

What is the pH scale;

Answer 16

A scale that measures how acidic or basic a substance is, with numbers ranging from 1-14.

Question 17

Where does an acid fall on the pH scale?

Answer 17

any pH less than 7.

Question 18

Where does a base fall on the pH scale?

Answer 18

any pH greater than 7

Question 19

Define a neutral substance.

Answer 19

It is neither acidic nor basic, it contains the same amount of hydrogen and hydroxide ions. It falls on 7 in the pH scale.

Question 20

What is the general reaction for neutralisation?

Answer 20

acid + base -> salt + water

Question 21

What is the general reaction for acids and metals?

Answer 21

acid + metal -> salt + hydrogen gas

Question 22

What is the general reaction for acids and carbonates?

Answer 22

acid + carbonate -> salt + water + carbon dioxide

Question 23

What is the general reaction for acids and digestion?

Answer 23

hydrochloric acid + sodium hydrogen carbonate -> sodium chloride + water + carbon dioxide

Question 24

What is a process in digestion that allows food to be digested?

Answer 24

Saliva in your mouth is slightly basic, so it helps to neautralise some of the acids that you eat like orange juice.