Unit 2.1 - elements, mixtures and compounds

Question 1

Define element

Answer 1

Elements are the simplest substance that cannot be broken down into anything simpler using chemical reactions; a substance made from one one type of matter/atom. Fixed properties, fixed composition.

Question 2

Define compound

Answer 2

A substance made from 2 or more different elements chemically combined; can be chemically but not physically broken down. They have completely different properties from the elements from which they were made. Fixed properties, fixed composition.

Question 3

Define mixture

Answer 3

A substance made up of 2 or more pure substances physically combined together; mixtures can be physically separated with different methods. Mixtures keep the properties of the substance from which it was made from. Not fixed properties, not fixed composition.

Question 4

What are the 2 types of mixtures and the difference between them?

Answer 4

1. Solution - a soluble solid/liquid/gas dissolved in another liquid. They are made up of a solvent (the major component in which the solid dissolves, e.g. water) and the solute ( the minor component which is being dissolved, e.g. salt). An aqueous solution is a solution where the solvent is water. Solutions are transparent, but some may be colored.
   Suspensions - a mixture where an insoluble solid is spread through a liquid. The solid settles at the bottom (e.g. chalk and water). Suspensions are opaque

Question 5

What does it mean when a solution is concentrated, dilute, and saturated?

Answer 5

Concentrated - large amount of dissolved solute compared to solvent
Dilute - small amount of dissolved solute compared to solvent
Saturated - solution has maximum concentration or solute at specific temperature

Question 6

What is a pure substance?

Answer 6

A substance that is made from only 1 type of particle (element or compound) and have consistent/specific properties such as melting points

Question 7

What is boiling point elevation?

Answer 7

When a solute that does no easily evaporate is added to water, the boiling point of water is elevated. Water boils when vapor pressure (how much vapor is being produced by a liquid at a certain temperature) = atmospheric pressure. Dissolved salt ions block the water molecules from evaporating, meaning that that it takes longer for vapor pressure to equal atmospheric pressure, which results in a higher boiling point. The opposite can be said for the melting point, which drops when salt is added.