Solutes and the freezing point of Water

Phase change Substances undergo changes in phase: SolidLiquid LiquidGas Phase changes requires a transfer of energy. Exothermic: the phase change results in a release of energy. Endothermic: the phase change results in an absorption of energy. During freezing water molecules lose energy and become more ordered. what type of energy transfer would that be? Ice melting absorbs energy from it’s surrounding. What type of energy transfer would that be?

Heating & Cooling Curve Graphs Visually represent what is occurring during phase changes. What is happening to kinetic energy as time progresses in the heating curve? Cooling curve?

Solute Addition Solute addition to water can change the physical properties of water. The addition of an electrolyte to water results in the ability of water to conduct electricity. The addition on non-electrolytes will not allow this to happen. Remember: Electrolytes are ionic compounds, like NaCl, which ionize into cations and anions. Remember: Non-electrolytes are covalent compounds, like sugar, which do not dissociate in water. Freezing point and boiling point, like conductivity, may also change with the addition of a solute.

How does the addition of different types of solutes affect the freezing point of water? Determine how the addition of electrolytes and non-electrolytes affect the freezing point of water. With your group develop a hypothesis to answer the question. Using the available materials develop an investigation to collect evidence that will support your claim. Conduct your experiment Analyze data Present your argument- group poster or individual

procedure Hints Using rock salt and ice a supercool environment can be generated (less than 0*C) in your Styrofoam cup. The aqueous solutions you test should have a concentration between .5-1.0M. Mix 100mL of distilled water & solute in an Erlenmeyer flask until all solute is dissolved. Before you begin answer the investigation proposal questions on your lab.

Available Materials Tools Solute NaCl Sucrose Isopropyl Alcohol KCl Test Tube Test Tube Clamp Ring Stand Thermometer Foam Cups DI Water Ice Rock Salt NaCl Sucrose Isopropyl Alcohol KCl NaNO3