Elements, Compounds, Mixtures

Question 1

What is an element?

Answer 1

Made of 1 type of atom only eg: Zn, Mg, Oz, Coo

Example: Zinc (Zn) is an element

Question 2

What is a compound?

Answer 2

Made of 2 or more different elements joined eg COz, H20, CHa, AlzOs

Example: Water (H2O) is a compound

Question 3

What are mixtures?

Answer 3

2 or more elements or compounds not chemically joined. Eg salt dissolved in water, gases in air, hydrocarbons in crude oil, sand and water, alcohol and water

Question 4

How can mixtures be separated?

Answer 4

Filtration: solid gets trapped in the filter paper.
Crystallisation: evaporate the water to leave solid crystals.
Distillation: Evaporate then collect vapours and condense. Chromatography: Dissolved chemicals move different distances up the paper (Rr values different for different chemicals)

Question 5

What is the atomic structure?

Answer 5

Protons and neutrons in nucleus. Electrons in energy shells around nucleus. 2 max in first shell and 8 max in next 2 shells. Atomic mass is the protons and neutrons added together as both have a mass of 1. Electrons mass is virtually zero so it is not included in the mass of an atom. Size of atoms around 1x 10-1 (0.1nm)