Teacher Demo: Bright Star or Close Star?

When you gaze up in the night sky, some stars will be very bright while other stars are barely visible to the unaided eye. With the aid of binoculars, you may be able to observe different colours in the stars. The brightness and colour of a star depends on three factors: temperature, distance, and size.

There are two measures of how bright a star appears:

  • The “apparent magnitude” of a star describes how bright the star appears from Earth. This scale ranges from the brightest star in the sky, the Sun, which is set at –26.8. The dimmest stars, which are only visible with the largest telescopes, have an apparent magnitude of 25. The faintest stars visible by the naked eye have an apparent magnitude of 5.5. A decrease of 1 on the scale represents a 2.5 times increase in the apparent brightness.
  • The absolute magnitude of a star is the measure of brightness of a star if it were at a distance of 32.6 light years (ly) from an observer. By placing all stars at this distance, the true brightness of the stars can be compared.

We know that the apparent magnitude of the Sun is the brightest at –26.8. However, when using the absolute magnitude scale, the Sun would be barely visible to the naked eye, with a reading of 4.8.

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Student Activity: Sock Mitosis

This demonstration is a great way for students to model the stages of mitosis. Images of the different stages in textbooks are static snapshots and many students have difficulty grasping the idea that mitosis happens as part of a continuous cycle.

What happens?

Students will observe a model going through each stage of mitosis.

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Student Activity: Predators in Control

Predator–prey relationships are one of the most important biotic relationships in the sustainability of an ecosystem. Predators are the natural controls in an ecosystem, limiting the size of a prey population. Many studies have illustrated that the long-term sustainability of an ecosystem is severely affected if top predators are eliminated. Prey populations increase as a result of the loss of their natural predators and they overgraze the vegetation resulting in ecosystem collapse.

Top predators―including wolves, grizzly bears, sea otters, and alligators―are referred to as keystone species. They are crucial in maintaining and sustaining ecosystem function. For example, on the west coast of Canada the loss of sea otters, a keystone species, has led to an increase in populations of sea urchins and other shellfish which are overgrazing on the underwater kelp forests and destroying the habitat of many different organisms.

This game models the interrelated effects of predator (fox) and prey (rabbit) populations over several generations.

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Borax Slime Activity Concerns Update

Borax Advisory Update Health Canada

Health Canada issued an advisory this past summer, suggesting that exposure to boron substances be reduced as much as possible from all sources. They identified boron substances as a developmental and reproductive health risk. They also stated that parents should not make slime and putties with borax and boric acid. By extension, teachers began to question the safety of making slime in their science classes. In response to questions posed by the STAO Safety Committee, Health Canada has clarified their advisory issued this past summer.

Regarding the use of Borax/Boric Acid, Health Canada wrote:

The proper use of gloves and goggles will reduce exposures to chemical substances. The main concern with the use of boron containing substances for making slimes or putties, is with accidental or intentional ingestion. This ingestion hazard is mainly targeted at young children who are prone to hand-to-mouth activities.

High school students, who have received proper training in hazardous material handling, and who are properly supervised to prevent ingestion, would be at low risk of exposure to boron, or other hazardous materials used as part of a science curriculum. The safe disposal of any boron containing substances should be closely monitored to prevent accidental or intentional ingestion.

Students younger than high school age, and those who have not been properly advised in the safe handling of laboratory chemicals should not be using borax, or any other hazardous chemicals at home or in a school setting.

Suggestions for activities involving borax or boric acid:

Although the chemicals containing boron do not readily cross the skin barrier, steps could be taken to prevent skin contact. Students could be issued gloves or alternatively, the ingredients for slime could be placed in a sealed plastic bag and then mixed. Students should be instructed to wash their hands at the end of the lab activity. Teachers should then collect the slime prior to dismissal to ensure that accidental or intentional ingestion does not occur. The slime can then be thrown out with the regular garbage.

Some suggested safer alternatives, for making slime or putties involving glue, have a high volatile organic compound (VOC) content and release this into the air. However, other glue and borax free recipes are available on-line and teachers are encouraged to explore the use of these safer alternatives.

We hope that the information in this response will help you in making an informed decision as to the use of boron containing substances in teaching science. Our safety committee can be contacted with your safety questions at info@stao.org, attention STAO Safety Committee.
Dave Gervais
Chair STAO Safety Committee


Sources of Light Cooperative Learning Activity

Idea- lightbulb ImageBy Varsha Patel, TDSB


I chose to cover luminous sources using this cooperative learning activity (CL) as a way to make the topic more interesting and meaningful to the students. Students can be easily grouped according to the light source for which they are responsible, another reason why this activity works well. It is truly remarkable that once all the instructions (see Instructions sheet) were given out, the students were engaged — working quietly and attentively as they knew they all had roles to perform. Giving a time limit for the various parts of the activity ensured students maintained their level of readiness/involvement.

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