Boiling water. A phase change occurs when water boils.
The three common phases are <em>solid</em>, <em>liquid</em>, and <em>gas</em>. A <em>phase change</em> happens when one phase changes into different phase without a change in chemical composition.
When water boils, the liquid phase becomes a gas (water vapour or steam). The water does not change its chemical composition be each phase consists of water.
Thus, boiling water involves a phase change.
Mixing paint does <em>not</em> involve a phase change because it stays a liquid during all stages of the mixing.
A suspension consists of two phases, but the phases do not change into other phases.
When 2-pentanol gets oxidized you end up with 2-pentanone. In this case, since we are oxidizing a secondary alcohol you end up with a ketone. They cannot be oxidized further than that. If it was a primary alcohol you would end up with an aldehyde.
You can find the mechanism as well the molecule formula of both 2pentanol and 2pentanone attached.
Answer: b. One atom transferring electrons to another atom
Explanation: An ionic bond is formed when an element completely transfers its valence electron to another element. The element which donates the electron is known as electropositive element and the element which accepts the electrons is known as electronegative element. This bond is formed between a metal and an non-metal.
Covalent bonds are formed by sharing of electrons between non metals
For example, In calcium iodide the one electron from calcium metal gets transferred to iodine atom and thus form an ionic bond to give 
Electronic configuration of calcium:
![[Ca]=1s^22s^22p^63s^23p^64s^2](https://tex.z-dn.net/?f=%5BCa%5D%3D1s%5E22s%5E22p%5E63s%5E23p%5E64s%5E2)
Calcium atom will lose two electron to gain noble gas configuration and form calcium cation with +2 charge.
![[Ca^{2+}]=1s^22s^22p^63s^23p^6](https://tex.z-dn.net/?f=%5BCa%5E%7B2%2B%7D%5D%3D1s%5E22s%5E22p%5E63s%5E23p%5E6)
Electronic configuration of iodine:
![[I]=1s^22s^22p^63s^23p^64s^23d^{10}4p^5](https://tex.z-dn.net/?f=%5BI%5D%3D1s%5E22s%5E22p%5E63s%5E23p%5E64s%5E23d%5E%7B10%7D4p%5E5)
Iodine atom will gain one electron to gain noble gas configuration and form iodide ion with -1 charge.
![[I^-]=1s^22s^22p^63s^23p^64s^23d^{10}4p^6](https://tex.z-dn.net/?f=%5BI%5E-%5D%3D1s%5E22s%5E22p%5E63s%5E23p%5E64s%5E23d%5E%7B10%7D4p%5E6)
Calcium
this is because calcium will lose will lose more electrons and is a group 2 metal, copper is a transition metal which is a lower position and more stable than calcium.
break down food into smaller molecules the body can use; absorb molecules into blood and carry them throughout the body; eliminate wastes from the body
