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Lab Techniques: Measurement, Temperature Control, and Timing

← Builds on Freezing Point Depression and Ice Cream Science

Terms you will need

  • freezing point depressionWhen you add something that doesn't evaporate to a liquid, the liquid freezes at a lower temperature than it would by itself.
  • caseinCasein is a type of protein found in milk that helps form cheese and is used in food and glue.
  • colligative propertiesColligative properties are traits of solutions that depend on how many particles are in the solution, not what those particles are.
  • curdCurd is the solid part that forms when milk is turned into cheese, made when casein proteins clump together.
  • denaturationDenaturation is when a protein loses its shape and function, often because of heat, acid, or other treatments.
  • phpH is a measure of how acidic or basic a solution is, based on the amount of hydrogen ions in it.

How this topic runs

  1. 1Start here
  2. 2How it works
  3. 3At competition depth

Figures (2)

This image contains two equilibrium reactions. The first shows a C atom bonded to three H atoms and another C atom. The second C atom is double bonded to an O atom and also forms a single bond to another O atom. The second O atom is bonded to an H atom. There is a plus sign and then the molecular formula H subscript 2 O. An equilibrium arrow follows the H subscript 2 O. To the right of the arrow is H subscript 3 O superscript positive sign. There is a plus sign. The final structure shows a C atom bonded the three H atoms and another C atom. This second C atom is double bonded to an O atom and single bonded to another O atom. The entire structure is in brackets and a superscript negative sign appears outside the brackets. The second reaction shows C H subscript 3 C O O H ( a q ) plus H subscript 2 O ( l ) equilibrium arrow H subscript 3 O ( a q ) plus C H subscript 3 C O O superscript negative sign ( a q ).
This table has two main columns and four rows. The first row for the first column does not have a heading and then has the following in the first column: Initial concentration ( M ), Change ( M ), Equilibrium concentration ( M ). The second column has the header of “H subscript 2 C O subscript 3 plus sign H subscript 2 O equilibrium arrow H subscript 3 O superscript positive sign plus sign H C O subscript 3 superscript negative sign.” Under the second column is a subgroup of three columns and three rows. The first column has the following: 0.033, negative sign x, 0.033 minus sign x. The second column has the following: approximately 0, positive x, x. The third column has the following: 0, positive x, x.

Lab techniques like measurement, temperature control, and timing are essential for accurate scientific experiments. In experiments, you might measure how much a solute dissolves in a solvent, control the temperature to see how it affects the solution, or time how long it takes for a chemical change to happen. These techniques are used in many areas, from food science to chemistry.

One key concept in lab work is colligative properties. These are properties of solutions that depend on how many solute particles are in the solution, not what kind of particles they are. For example, adding salt to water lowers its freezing point and raises its boiling point.

This happens because the salt particles interfere with how water molecules behave. The more particles you add, the more the freezing point drops and the boiling point rises. This is why salt is used to melt ice on roads in winter.

Osmosis is another important process in lab techniques. It happens when water moves through a membrane from a less concentrated solution to a more concentrated one. In reverse osmosis, pressure is used to push water the other way, which is how some water purification systems work.

This technique is used in many settings, from large desalination plants to small home filters.

Key Points

  • Freezing point depression is the decrease in freezing point of a dilute solution compared to that of the pure solvent, directly proportional to the molal concentration of the solute.
  • Casein is a family of related phosphoproteins commonly found in mammalian milk, comprising about 80% of the proteins in cow's milk.
  • Colligative properties are those properties of solutions that depend on the ratio of the number of solute particles to the number of solvent particles in a solution, and not on the nature of the chemical species present.

Terms

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