science

How are the following terms different? Matter, substance, element, compound, atom, and molecule?

Imagine baking a cake.
All matter is made up of particles called atoms. There are different types of matter such as solid, liquid, or gas. Solid chocolate, liquid oil, and gaseous water vapor are all matter.
Atom is a small particle and the building block of matter. It is like a grain of sugar.
An element is a substance made of only one kind of atom and can be solid, liquid, or gas, such as gold (Au) and silver (Ag).
A molecule is two or more, same or different, atoms joined together. Some elements are molecules. They can consist of two of the same atom such as oxygen gas (O₂) made up of two oxygen atoms. A different type of molecule, carbon dioxide gas (CO₂), is made up of different types of atoms, one carbon and two oxygen atoms.
A compound is a type of molecule that has different kinds of atoms from different elements. Water (H₂O) is a compound because it is made up of 2 hydrogen and 1 oxygen atom.
A substance is matter with a composition that is always the same. An element or a compound can be a substance.

How does air pressure affect the boiling point of water and why is it important to know that? What does that have to do with pressure cookers?

Imagine boiling water.
Air pressure is air that is all around us and pushes down on everything because it has weight.
When water gets hot enough for gaseous bubbles to form and it rises out of the water into the air.
The bubbles push against the air pressure pushing down on the water.
At normal pressure (sea level), water boils at 100°C.
Up in the mountains, the air becomes lighter and thinner and less air pressure is pushing down.
That is why it takes longer to boil water in the mountains.
Pressure cookers trap steam inside of the pot and increases air pressure.
Air pressure inside a pressure cooker becomes very high which means that water cannot boil at 100°C. The boiling point becomes higher.
Food cooked inside a pressure cooker cooks faster because of the higher temperature.

Imagine boiling water.
Air pressure is air that is all around us and pushes down on everything because it has weight.
When water gets hot enough for gaseous bubbles to form and it rises out of the water into the air.
The bubbles push against the air pressure pushing down on the water.
At normal pressure (sea level), water boils at 100°C.
Up in the mountains, the air becomes lighter and thinner and less air pressure is pushing down.
That is why it takes longer to boil water in the mountains.
Pressure cookers trap steam inside of the pot and increases air pressure.
Air pressure inside a pressure cooker becomes very high which means that water cannot boil at 100°C. The boiling point becomes higher.
Food cooked inside a pressure cooker cooks faster because of the higher temperature.

Why is it not a good idea to use mass to identify a substance? Is there a better property for doing so? Which one? Why?

It is not a good idea to use mass to determine what a substance is.
Mass only tells us how much of something not what that something is.
Imagine 1kg of pure gold (Au) and 1kg of pure aluminum (Al). They will have the same mass or weight, but be very different in size and volume.
Density is a property that measures how much of something (mass) there is packed into a certain volume.
Every type of pure substance has its own density.
No matter how big or small, a substance's density will always stay the same.
In a pure substance, density tells us how tightly packed the particles are.
Density for a pure substance always stays the same, so it is a good way to identify substances.
Density is better than mass when you want to identify a substance.

Making a Saturated Solution

How many teaspoons of salt do we need to saturate 100mL of 1. hot water and 2. cold water?

Why was it easier to saturate the solution with cold water?

Symbiosis is a biological term that means a close, long-term relationship between two different species. These relationships can help both organisms, help one without affecting the other, or help one while harming the other. What makes a relationship symbiotic is that the organisms depend on each other in some way. One example is clownfish and sea anemones. The clownfish hides in the anemone’s tentacles for protection, and the anemone benefits because the clownfish cleans it and brings food. This is called mutualism because both organisms benefit. Another example is tapeworms living in mammals. Tapeworms take nutrients from the host, which harms the host. This is parasitism because one organism benefits while the other is harmed. A third example is barnacles on whales. Barnacles attach to the whale and move with it, while the whale is not affected. This is called commensalism.

When we think of Taiwan as an ecosystem, the human population is limited by several factors that affect how much it can grow. One major factor is land. Taiwan is a mountainous island, so there is not much flat land for homes, farms, and factories. This limits where people can live and work. Another limiting factor is natural resources, especially fresh water and energy. Taiwan depends on rainfall and reservoirs for water, and droughts can cause shortages. Taiwan also imports most of its energy, so problems in other countries can affect supply. Food is another factor. Although Taiwan grows some food, it imports a large amount. As the population grows, it becomes more dependent on other countries. Finally, natural disasters such as typhoons, earthquakes, and rising sea levels can damage cities and resources, making it harder for the population to grow.

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