Activity 38 Analysis

1. Which solvent/solute pairs dissolved completely? What is you evidence?

• Water completely dissolved starch, sugar, sodium chloride, and copper sulfate

• Ethanol dissolved only lauric acid• Evidence is

formation of a clear liquid (could be colored or colorless) Disappearance of all solids

2. a. Which solvent/solute pairs seemed not to dissolve at all? What is your evidence?• Water didn’t dissolve lauric acid or neroline yara yara• Ethanol didn’t dissolve starch, sugar, sodium chloride,

and copper sulfate• Evidence is that the solids left in the cups appear to be

the same amounts as were added

b. In these cases how might you test to be sure you are correct that none of the solute dissolved?• Filter the solid• Evaporate off the solvent from the liquid that flows

through

3. Which solvent/solute pairs dissolved partially? What is your evidence?

• Water partially dissolved iron chloride• Ethanol partially dissolved iron chloride and

neroline yara yara.• Evidence

Liquid turned colored Some of the solid remained undissolved Neroline yara yara in ethanol didn’t change color Could tell some of it disappeared

4. Thinking back to Activity 37, “What Dissolves?” explain the connection between the terms solubility and saturation.

• Solubility describes how well a particular solute dissolves in a particular solvent

• The more soluble the solute is, the higher the amount of it that can dissolve before the solution becomes saturated

Warm up• In the warm up section of your

notebook, answer analysis question #5 from activity 38.

• Create a concept map using the following list of terms:– Soluble– Dissolved/dissolves– Solute– Solvent– Saturated– solution

Concept Map: Solubility

What do you think determines how much of a substance dissolves?

• The identity of the solvent and solute determine whether some dissolving is going to occur

• How much something dissolves or whether the solution becomes saturated depends on the relative amounts of solvent and solute

Water is the most effective solvent known and is often referred to as the universal

solvent

Water has polar covalent bonds

Title: Contaminants and the Water Cycle

Activity 39

Talking Drawing: Contaminants and the Water Cycle

• Label places that contain water

• Draw arrows showing water’s possible movement

• Label places where water could get contaminated and name the type of contamination

What are the forms of water found on earth?

Solid liquid vapor

Ice rain water vapor

Snow seawater

lakes

rivers/streams

Are these phase changes chemical or physical changes?

Read C-47

Problem: How does water move from place to place and pick up contaminants as it moves?

Hypothesis/Initial Thoughts:

Background:• A drop of water contains many billions of

water molecules

• Water molecules have the same composition in their vapor, liquid, and solid states

• These states differ in how close together and how rigidly held together the molecules are

The Activity• You will take an imaginary journey with a

molecule of water– As it collects to form a drop with other molecules– As it falls to earth as precipitation– And joins others that are traveling on the water cycle

• The large collections of molecules go through the water cycle many times, picking up and leaving behind biological and chemical contamination

• Individual molecules do not stay with the same collection of molecules, but encounter many other molecules as they go through the cycle

Procedure• Organisms are living things, from single-celled

bacteria to elephants.• The molecules of water in this water droplet must

go to the general location defined by the roll of the white number cube (such as the atmosphere).

• You can choose to have those molecules be in any state or place within the general location and are not restricted to choosing one of the descriptions listed on the cards.

• You may designate a specific location where a drop of water might be, such as a drainpipe and a tree near a river.

Procedure

• This activity models real-life.

• You may not go to every location of the water cycle and you may go a location more than once.

• A higher percentage of water is found in certain locations (the ocean), so you may spend more time there.

My Water Cycle Story