Dissociation & Rate of Dissolving Bundle 4: WateR, Solubility, and ph

Watch the following video and write down your observations engage Watch the following video and write down your observations

QUICK WRITE – 2 Minutes What did you see happen in the video? Now, turn to your table partner and together discuss what happened and draw it on the paper provided. Be prepared to share with the class.

Table Talk – 1 minute Question: Why do the water molecules orient themselves differently around the anions and cations in salt? Answer: electrical attraction Because Water is polar! The Water Molecule has charged ends so the positive end of a water molecule is attracted to the negative chlorine ion, and the negative end of a water molecule is attracted to the Positive sodium ion.

Dissociation Dissociation (Dissolving) is a process where the positive and negative ions of a substance come apart as an ionic compound dissolves in a solvent, like water. Dissociation is reversible because the original ionic compound does not change, therefore dissociation is a physical change ONLY Ionic compounds dissociate

Dissociation of Ionic compounds Dissociation is a separation of ions that already exist.

activity At your table, create a picture of the dissolving of salt ions in water using the ion and water molecule pictures. Color the ions and water molecules as instructed below: Sodium – green Chlorine – red Oxygen – blue Hydrogen – orange Glue or tape your pictures in your ian notebook showing the correct configuration of water molecules around the salt ions When finished, your teacher will stamp your picture if it is correct

Question If you wanted to dissolve a substance in water quickly, what are some things you could do to make it happen faster?

DEMO What factors do you think affect how quickly something dissolves?

Rate of dissolving There are 3 factors that affect the rate at which a substance will dissolve in water. Agitation Increased surface area Increased temperature

AGitation Agitating mixture (stir, shake) - moves dissolved solute particles away from contact surfaces more quickly allowing new collisions between solute and solvent. Ex. Sugar stirred in tea vs. unstirred.

Increased Surface Area a greater Surface Area allows more collisions to occur. The surface area can be increased by crushing or grinding the solute to change into powder Ex: sugar cube vs granulated sugar

IncreaseD temperature increases the KINETIC energy (energy of movement) resulting in more frequent collisions with greater energy. Ex. Sugar dissolves faster in hot tea than in cold tea.

Rate of dissolving lab Go to your assigned lab table Complete the three tasks in 10 minutes or less Answer the guided questions Return to your seat and write your summary of the lab Be prepared to share with the class