What is the difference between a change in demand and a change in quantity demanded?

Answer 1

In economics, demand is defined as the quantity of a good or service consumers are willing and able to buy at a range of prices.

A change in demand occurs when a demand factor/conditionchanges. The four main demand factors are:

• Consumer tastes, fashions and preferences.
• Consumer income.
• The price of substitute goods.
• The price of complimentary goods.

A change in demand is shown visually as a shift of a demand curve.

Quantity demanded is defined as the quantity of a good or service consumers are willing and able to buy at a price.

A change in quantity demanded is caused only by a change in price. The law of demand states that as the price of a good or service increases (ceteris paribus), the quantity demanded will decrease (and vice versa). A change in quantity demanded is shown visually as a movement along a demand curve.

Ceteris paribus is a Latin term; it is used in economics to signify that all demand/supply factors remain unchanged.
A change in Demand is affected by either a change in productivity or a change in the price of a certain product. And a change in the quantity demanded is affected by either Immigration( a large increase in the quantity or laborers) and an shift in minimum wage.
Change in quantity demanded as illustrated in a demand curve is the movement along the curve or the response in quantity demanded due to a change in price.

Change in demand as illustrated in a demand curve in the movement OF the curve or the expansion or contraction of the demand. (e.g. more consumers in the market)
Demand: the people's desire to purchase something.

For example, when the Apple iPod came out, it was in high demand so the suppliers had to make more of them quickly because they were running out and were wanted by the people

Quantity: A particular or indefinite amount of something.

For exmaple, 2 fish are swimming the the lake. The ocean has a vast amount of water
change of demand means increase or decrease in demand due to change in the price of the commodity other than other factors that affect demand.but however change in quantity damand means increase or decrease in demand due to change in factors that affect demand apart from the price of the commodity.
A change(shift) in demand refers to a change in the amount of a product or service demamded in regards to changes in expectations,income,Demographics,substitutes and expectations and will cause a "shift" in the demand curve. A change in quantity demanded refers to a change of the inputs(resources required to produce that good or service) required to produce the goods or services being demanded. If the price of producing the good or service changes then the quantity demamded will "change" causing a movement along the demand curve.