Science Experiments and Lab Materials

Posted on Dec 4, 2024 in Chemistry

Science Education

Questions for Teachers about Teaching Models

Teachers should consider the following questions when planning science lessons:

  1. Who will lead the teaching?
  2. When will specific knowledge be transmitted?
  3. What knowledge will be transmitted?
  4. What content will be conveyed?
  5. What methodology will be used to transmit knowledge?

Historical Methods of Teaching Science

  • Evolutionary Method
  • Biographical Method

Evolutionary Method

This method involves explaining a scientific subject or phenomenon by starting with early explanations and progressing to more advanced, current understandings. A disadvantage is the time required, potentially omitting parts of the curriculum. However, it benefits students by demonstrating that current theories may not be definitive and older theories may still hold value. This method is best used selectively for specific topics, such as:

  • Light
  • Atomic theory of matter
  • Radioactivity
  • Theory of solutions

Biographical Method

This method connects the explanation of a phenomenon or subject to the lives of scientists who have made significant contributions to its study. While it can enrich student understanding, it can also be time-consuming, potentially detracting from other important topics. It’s best used sparingly, incorporating anecdotes or short biographies rather than extensive life stories. Some notable scientists for a physics and chemistry program include:

  • Archimedes
  • Copernicus
  • Galileo
  • Priestley
  • Rutherford
  • Lavoisier
  • Faraday
  • Einstein
  • Madame Curie

Module 2: Laboratory Materials

Porcelain Capsules

Porcelain capsules are used for heating solutions to dryness, ensuring complete solvent evaporation.

Crystallization

Crystallization is based on the difference in solubility at different temperatures. For example, if 100 grams of water at 80°C can dissolve 60 grams of a substance, and 100 grams of water at 15°C can dissolve 20 grams, then cooling a saturated 80°C solution to 15°C will result in 40 grams of crystallized substance.

Percentage by Weight of a Solution

This is calculated by dividing the grams of dissolved substance by the grams of solution and multiplying by 100.

Alloys

An alloy is a solid solution of two or more metals, typically formed by melting them together. Examples include:

  • Bronze (copper and tin)
  • Brass (copper and zinc)

Volume and Capacity

Volume is the space occupied by a body, measured in cm3. Capacity is the measure of the internal volume of a container, measured in ml or L.

The volume of a test tube refers to the space it occupies (including glass and walls), while its capacity refers to the volume of liquid it can hold.

The units cm3 and ml are often used interchangeably because 1 L (the volume of 1 kg of water at its maximum density) is equal to 1,000.028 dm3.

Determining the Volume of Irregularly Shaped Objects

Fill a test tube with a known volume of water. Carefully add the object to the test tube and observe the increase in water level to determine its volume.

Parallax Error

Parallax error occurs when viewing a scale at an angle. To avoid this, view the scale straight on, perpendicular to the markings.

Density

Density is the ratio of a body’s mass to its volume.

Specific Gravity

Specific gravity is the ratio of a substance’s density to the density of a reference substance (usually water).

Density of a Solution

The density of a solution is calculated by dividing the mass of the solution by its volume.

Factors Influencing Dissolution

  • Fragmentation (particle size)
  • Heat
  • Agitation (stirring)

Asbestos

Asbestos is known for its resistance to high temperatures and is used in fire-resistant clothing and theater decorations. However, it is a carcinogen and poses health risks.

Types of Flasks

  • Distillation flask
  • Volumetric flask
  • Erlenmeyer flask
  • Kitasato flask

Volumetric flasks should not be heated as this alters their calibrated volume. Other flasks, such as Erlenmeyer and distillation flasks, can be heated.

Water Pump

A water pump creates a vacuum in a flask. Water enters through the top, connects to the vacuum flask on the side, and exits through the bottom drain.

Filtration

There are two types of filtration: ordinary and vacuum (reduced pressure).

Using a Separatory Funnel

A separatory funnel is used to separate immiscible liquids based on their densities. After allowing the liquids to settle, the denser liquid is drained through the stopcock, followed by the less dense liquid.

Cacodyl Oxide

Cacodyl oxide has a foul odor, is poisonous, and is highly flammable.

Radicals

A radical is a group of atoms that remains unchanged during a series of chemical reactions.

Spectroscope

The spectroscope was invented by Bunsen and Kirchhoff.

Test Tube Rack

A test tube rack is used to hold test tubes.

Heating Liquids in Test Tubes

When heating a liquid in a test tube, angle the tube so the opening is not pointed towards anyone. Heat gently to avoid boiling over.

Pipette

A pipette is a long glass tube used to transfer liquids. It can be graduated (marked with measurements) or volumetric (designed to deliver a specific volume).

To use a pipette, suction the liquid into the tube, control the flow with a finger on the top, and release the liquid by removing the finger.