Cooking: temp of a warm object

Cooking means constant self-tutoring. The tutor speculates about the actual temperature of a warm object.

Yesterday I took a glass casserole dish of mac and cheese from the oven. Its baking temp was 177C.

An hour later, most of the mac and cheese had been served from the dish. Moving it, I was surprised how warm it still was to the touch.

Yet, how warm was it? I didn’t have a convenient way of measuring, so I opened a browser tab and found, whose members seem to agree that about 60C is dangerous to touch for more than a second or two.

The casserole dish wasn’t hot; rather, just surprisingly warm. I’d estimate it was about 40C.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Botany: black walnut: juglone

The tutor researches the effects of juglone from black walnut trees.

Juglone is a toxin produced by the black walnut tree; it’s found throughout the tree and in its leaves, shells and nuts.

Apparently, to humans eating the walnuts, the juglone is not a problem. However, it enters the soil from the roots of the black walnut tree, as well as from its leaves, twigs, and even pollen falling to the ground – not to mention the nuts and their shells. Some plants, such as tomatoes, potatoes, lilacs, and rhododendrons, can be damaged by the juglone.

To be safe, composted matter from black walnut should wait a year or more before application.

Horses are particularly sensitive to juglone; neither black walnut shavings, nor the husk fibre, etc, should be used in a horse’s environment.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Stainless steel: magnetic or not?

The tutor investigates the idea that stainless steel is non-magnetic.

I’ve heard from more than one source that stainless steel is non-magnetic: if you put a magnet to it, there isn’t attraction like you might expect with “ordinary” steel.

According to Scientific American, some stainless steel is magnetic, but the most common kind (Type 304) isn’t. What makes Type 304 nonmagnetic: its content of nickel, manganese, carbon, and nitrogen.

Stainless steel made from just iron and chromium (13 to 18 percent Cr) likely will be magnetic.

The presence of certain elements in the steel affects its atomic pattern; some patterns result in magnetic attraction, while others do not.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology: protists: diatoms

The tutor mentions a few points about diatoms.

In my Feb 4 post I introduced protists, which constitute a kingdom of eukaryotic, mainly single-celled organisms. Protists are divided into plantlike and animal-like ones.

Diatoms, from phylum Chrysophyta, are among the golden brown algae. They are plantlike protists, perhaps the most numerous of them. In the oceans, their abundance makes them a major food source at the base of the ecosystem. Furthermore, they are prominent producers of oxygen on Earth.

Diatoms have a two-valve structure, rather like the base and lid of a box. They are well known for having glass (silica) in their cell walls, which show striking patterns under a microscope.

Diatoms have been even more abundant in the past; today, those fossils constitute diatomaceous earth, which is mined for applications such as soundproofing, filtration, and scouring powders.



Mader, Sylvia S. Inquiry into Life, 9th ed. Toronto: McGraw-Hill, 2000.

Ritter, Bob et al. Biology. Scarborough: Nelson Canada, 1996.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Physics: models of the atom

The tutor reviews the progress of thought about atoms through the ages.

Democritus, a Greek philosopher living around 400 BC, is credited as the first promoter of the concept of the atom. He proposed that all matter consists of tiny, indivisible particles, which he called atoms.

The next published refinement of Democritus’s idea was Dalton’s atomic theory of 1808. He agreed with Democritus, elaborating the idea of an element – a type of atom. Every element has its unique type of atom.

After further study came the Thomson model, in common use from the 1890s to 1911. It was also called the “plum pudding model”, and proposed that an atom consists of positively charged “dough” with negatively charged “raisins” scattered throughout. Thomson, who discovered the electron in 1897, realized that the electrons should be moving.

Rutherford, in 1911, carried out an experiment whose results led to the idea of the nucleus. The Rutherford model claims that the center of an atom is heavy and positive, while electrons orbit distantly around it. Most of the “volume” of an atom is empty space between the nucleus and the electrons.

The Bohr model (1913) refined the Rutherford model, suggesting that the electrons orbit at only certain distances (levels) from the nucleus, and that they can jump from one level to another. The levels are called shells.

Rutherford’s model is still used until high school; in grades 11 and 12, Bohr’s is studied.

In a future post I’ll explain Rutherford’s experiment and why it led to such a breakthrough.


Giancoli, Douglas C. Physics. New Jersey: Prentice Hall, 1998.

Bullard, Jean et al. Science Probe 10. Scarborough: Nelson Canada, 1996.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Physics: calculating force of friction

The tutor shows a basic example of calculating friction.

The force of friction, Ff, on a flat surface is given by

Ff = μFN


μ = coefficient of friction (often looked up from a table, or given)

FN = normal force: pushing force from surface to object at 90° to surface

Nearly always, FN = mg, where

m = mass of object

g = acceleration due to gravity (typically 9.8m/s2 on Earth)

Example 1: Calculate the force of friction between the tires and the road, dry conditions (μ = 0.40), for a 1400 kg car.


Ff = μFN = μmg = 0.40(1400)(9.8)= 5488N or 5500N in sig figs

I’ll be covering more about friction in coming posts:)


Heath, Robert W. et al. Fundamentals of Physics. D.C. Heath Canada Ltd., 1981.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Biology: protists (Kingdom Protista) vs bacteria (Kingdom Monera)

The tutor makes some comparisons between protists and bacteria.

Members of Kingdom Protista are generally single-celled organisms that live in water. They form a significant part of ocean plankton. Bacteria are typically single-celled as well, and are found virtually everywhere that supports life.

Unlike a Moneran (bacterium), a protist has a nucleus and organelles each separated from the cytoplasm by its own membrane. This distinction means that Monerans are prokaryotes, while Protists are eukaryotes.

While Protists may have appeared around 1.5 billion years ago, Monerans are much older, having possibly emerged 3.5 billion years ago.

I’ll be talking more about Monerans and Protists in coming posts:)


Mader, Sylvia. Inquiry into Life, 9th ed. Toronto: McGraw-Hill, 2000.

Ritter, Bob et al. Biology, BC ed. Scarborough: Nelson, 1996.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Fungi: reproductive cycle: zygospore fungi

The tutor comments about the reproductive pathways of zygospore fungi, including black bread mold.

With a zygospore fungus, such as black bread mold, the part you see above the surface comprises sporangia (singular: sporangium), which release spores. Spores have n chromosomes; they are haploid. Spores are released into the air. If a spore lands in welcoming conditions, it undergoes mitosis and develops into a new adult.

The more common situation is asexual reproduction, in which a single adult produces spores that repeat its own genetic signature.

Below the surface, the nonreproductive structures are the hyphae, which root throughout the growth medium (bread, for example). Zygospore fungi don’t have male and female individuals, but rather minus and plus. When hyphae from a minus and a plus touch, sexual reproduction occurs. First, each side forms a gametangium at the contact site. Inside each gametangium, gametes are produced. The two gametangia join externally, then, internally, their gametes fuse, forming zygotes, which are diploid (2n). The body in which the zygotes are encased develops a tough protective wall; it’s called a zygospore. This structure can endure adversity until favourable growth conditions resume.

When the zygospore detects promising growth conditions, meiosis occurs within. Then, the new haploid cells undergo mitosis in order to develop new adult bodies from which sporangia develop.

The life cycle described above is haplontic: the adult structures are always haploid (n). Only the zygote is 2n.


Mader, Sylvia S. Inquiry into Life, 9th ed. Toronto: McGraw-Hill, 2000.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Exponential growth: the growth constant, k

The tutor discusses the exponential growth constant with an example.

Let’s imagine a population, initially 100, doubles every 25 hours. To a biologist growing a culture, it’s probably an easy situation to consider.

Such a growth pattern would likely be modeled as follows:


where P is the population at any time t.

To find k, we’d use the fact that in 25 hours, the population will have doubled to 200:


Dividing both sides by 100, we arrive at


Taking the natural log of both sides, we find


Dividing both sides by 25, we come to


Therefore, the growth equation for this case is

    \[ P=100e^{\frac{tln2}{25}}\]

Generally, k, the growth constant, will be

    \[ \frac{ln2}{doubling\ time}\]



Larson, Roland E. and Robert P. Hostetler. Calculus, part one. Toronto:
  D.C. Heath and Company, 1989.


Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Calculator usage: The ENG function on the Casio fx-260solar

The tutor explains his recent understanding of a function he’s wondered about.

I’ve noticed the ENG function on more than one calculator, but have never used it. I’ve always assumed it means “engineering”; since I’m not one, it makes sense that I’m unfamiliar with it.

Yesterday my curiosity finally focused on this mysterious ENG function. You access it by SHIFT ÷ on the Casio fx-260solar. If you’re in COMP mode (I haven’t tried it with other modes), it seems to change the entered number to the highest power of 103 for which the number will be > 1. Examples:

0.056 SHIFT ÷ gives 56×10-3

0.000362 SHIFT ÷ gives 362×10-6

12037059.1 SHIFT ÷ gives 12.0370591×106

While I’m not an engineer, this notation is familiar to me. I know that in electronics, it’s common to refer to 0.056A as 56mA. Similarly, 0.000178A will likely by referred to as 178µA, also known as 178×10-6A. 12400000Ω would likely be referred to as 12.4MΩ (M=Mega=106).

I have more to say about the ENG function:)


Casio fx-260solar operation manual. London: Casio Electronics Co., Ltd.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.