Chem Unit 1- Reactions & equations

Question 1

Define “base”

Answer 1

Bases are bitter compounds that turn litmus or universal indicator blue or purple. When dissolved in water they produce (OH-) ions and are sometimes corrosive.

Question 2

Define “salts”

Answer 2

Compounds that are made up of metal atoms bound to non-metal atoms.

Question 3

Chemical formulae for the following acids:

• hydrochloric acid
• sulfuric acid
• nitric acid
• carbonic acid

Answer 3

HCl

H2SO4

HNO3

H2CO3

Question 4

Chemical formulae for these bases:

• sodium hydroxide
• potassium hydroxide

Answer 4

NaOH

KOH

Question 5

Define “acid”

Answer 5

Are sour tasting, corrosive compounds that contain hydrogen. They turn litmus and universal indicator red, orange or yellow depending on the strength. Acids are any substances that produce H+ ions when dissolved in water.

Question 6

Characteristics of a physical change

Answer 6

A physical change is a change of state. It is generally easy to reverse and no new substances are produced

Question 7

Characteristics of a chemical reaction

Answer 7

Substances are changed into different substances. a colour change is identified or a gas is released. Energy is either absorbed or released eg. Heat or light. A gas is released and bubbles are noticed. There is a formation of a solid - precipitate and the change is generally not easily reversed.

Question 8

The Law of Conservation of Matter

Answer 8

States that matter is never destroyed or created in chemical reactions. The particles of one substance are rearranged to form a new substance.
The same number of particles that existed prior to the reaction, will exist afterwards as well.

Question 9

Explain Endothermic reactions

Answer 9

Chemical reactions that absorb heat from their surroundings (perhaps making it colder) eg. An instant ice pack absorbs the energy from the sportsperson and in doing so makes the injury colder.

Question 10

Exoteric reactions

Answer 10

Involves the production or release of energy in a chemical reaction eg. burning (combustion) of gas in a laboratory.

Question 11

Sweating

Answer 11

ENDOTHERMIC reaction as the sweat absorbs the heat and makes the body feel better.

Question 12

Explain an element

Answer 12

An element is a pure particle that consists of 1 type of atom. It cannot be simplified of decomposed easily.

Question 13

Explain compounds

Answer 13

Pure particle consisting of 2 or more elements chemically bonded in a fixed ratio by mass, whose properties are different from the different original element.
Compounds can be decomposed chemically into either the elements that make them up or smaller compounds.