What elements make up water?
Click to see answer
Hydrogen and oxygen.
Click to see question
What elements make up water?
Hydrogen and oxygen.
What is the experiment mentioned in the notes?
Burning magnesium ribbon in air.
What happens when black iron filings and yellow sulphur powder are mixed?
They form a yellowish grey mixture without any heat change.
Give an example of a physical change.
The melting of ice.
What does the term 'property' refer to in chemistry?
Various characteristics of a substance.
What is solubility?
It refers to how well a substance (the solute) dissolves in another substance (the solvent).
What are some examples of physical properties?
Appearance, odour, taste, and hardness.
What is a characteristic of compounds?
Compounds have a fixed composition and specific chemical properties.
What is meant by 'change of state'?
A physical change in which no new substances are produced.
What happens to the properties of a substance during a physical change?
Some properties, such as appearance, may change.
What is the melting point?
The temperature at which a substance melts (changes from solid to liquid).
At what temperature does carbon dioxide and water vapor become solid during purification?
-80°C.
What is electrical conductivity?
The ability of a substance to transfer an electric current.
What is the observation for carbon dioxide in a limewater test?
Carbon dioxide turns limewater from colorless to milky.
Why is carbon dioxide important to life on Earth?
Even though it makes up about 0.03% – 0.04% of the air, it is essential for life.
What is a physical change?
A change in which no new substances are produced and the composition of a substance does not change.
What occurs when the mixture of iron and sulphur is heated strongly?
They react to form a new substance called iron(II) sulphide, releasing a lot of heat.
What does thermal conductivity refer to?
The ability of a substance to transfer heat.
What happens when a magnet is placed near the mixture of iron and sulphur?
The black iron filings are attracted by the magnet, while the yellow sulphur is not.
What are chemical properties of a substance?
Properties that describe the ability of that substance to react with other substance(s).
What is the observation expected from burning magnesium ribbon in air?
The magnesium ribbon burns brightly, producing a white light and forming magnesium oxide.
Do iron and sulphur retain their original properties in the mixture?
Yes, they retain their original properties.
Give examples of compounds.
Water, carbon dioxide, common salt, and sugar.
What method is used to separate the components of air?
Fractional distillation based on the difference in boiling points.
What does 'odour' refer to?
The smell of a substance.
What happens during the liquefaction stage of air separation?
The purified air is cooled and compressed, then allowed to expand, cooling further until it reaches -200°C to obtain liquid air.
What is the definition of a compound?
A compound is a pure substance made up of two or more elements chemically combined together.
How is the solubility of a substance in water defined?
As the mass (in grams) of the substance that dissolves in 100 cm³ of water at a particular temperature.
What elements make up carbon dioxide?
Carbon and oxygen.
What is a chemical change?
A change in which one or more new substances are produced.
What does ductility refer to?
How easily a solid can be pulled into wires.
How do the properties of compounds compare to their constituent elements?
Compounds can have very different properties from their constituent elements.
What process in plants is an example of a chemical change?
Photosynthesis.
What is the primary focus of Chapter 2 in the Form 4 Chemistry study notes?
The atmosphere.
What is the main difference between mixtures and compounds?
Mixtures consist of two or more substances that are physically combined, while compounds are substances formed when two or more elements chemically bond.
What are physical properties in chemistry?
Properties that can be determined without changing the substance into other substances.
What is the term for a physical change where a substance changes directly from solid to gas upon heating?
Sublimation.
What is an example of a chemical change involving magnesium?
The reaction between magnesium and oxygen to form magnesium oxide (MgO).
What happens to a glowing splint in the presence of oxygen?
Oxygen relights a glowing splint.
Is the condensation of steam on a cold surface a physical or chemical change?
Physical change.
How can mixtures be separated?
Mixtures can be separated by physical methods such as filtration, distillation, or chromatography.
Can the properties of a mixture be similar to its components?
Yes, the properties of a mixture can be similar to those of its individual components.
What is sodium chloride commonly known as?
Common salt.
What is produced when magnesium ribbon is heated in air?
Magnesium oxide (MgO).
How is density defined?
As the mass (in grams) of the substance per unit volume (in cm³).
What are hydrogen and oxygen classified as?
Elements, because they cannot be broken down further by chemical methods.
How do the properties of iron(II) sulphide compare to those of iron and sulphur?
Iron(II) sulphide has many properties that are different from those of iron and sulphur.
What is the boiling point?
The temperature at which a substance boils (changes from liquid to gas).
What elements are combined to form sodium chloride?
Sodium and chlorine.
What is a common use of carbon dioxide?
Making dry ice that acts as a refrigerant.
What is an example of a chemical change involving acids?
Acid-alkali neutralization.
Is the yellowing of newspaper after exposure to air a physical or chemical change?
Chemical change.
What happens to the properties of substances in a compound?
The properties of the individual elements change when they form a compound.
What is the common use of oxygen in the atmosphere?
Cutting and welding metals; making medical respirators to help patients with breathing difficulty.
What is the boiling point of nitrogen, and why is it significant in fractional distillation?
Nitrogen has the lowest boiling point at -196°C and boils off first during fractional distillation.
How are liquid oxygen and liquid argon separated in fractional distillation?
They are collected at the bottom of the fractionating column and further separated due to their close boiling points (-183°C for oxygen and -186°C for argon).
What is the approximate composition of air?
78% nitrogen, 21% oxygen, 0.9% argon, and 0.1% other gases.
What does 'hardness' refer to in the context of physical properties?
The ability of a substance to resist scratching.
What is the chemical equation for the formation of sodium chloride?
2Na(s) + Cl2(g) → 2NaCl(s)
Define a mixture.
A combination of two or more substances that retain their individual properties.
What is the first stage in the fractional distillation of liquid air?
Purification, where air is filtered and cooled to -80°C to remove carbon dioxide and water vapor.
What does malleability refer to?
How easily a solid can be rolled into sheets.
What are the two classifications of properties in chemistry?
Physical properties and chemical properties.
What is one example of a chemical change related to food?
Digestion of food.
What is electrolysis?
The decomposition of water into hydrogen and oxygen by passing electricity through it.
Is grinding a vitamin C tablet into powder a physical or chemical change?
Physical change.
What happens when the vapor from sublimation is cooled?
It changes directly to solid.
What is nitrogen commonly used for?
Food packaging and as a refrigerant for storing living cells and tissues.
Why is water not considered an element?
Because it can be broken down into hydrogen and oxygen.
What does 'taste' refer to in terms of physical properties?
The flavour of a substance.
How can sodium chloride be produced?
By burning a piece of sodium metal in chlorine.
What happens to dry cobalt(II) chloride paper when it comes in contact with water?
It turns from blue to pink.
Is the burning of petrol in a car engine a physical or chemical change?
Chemical change.
What is a common chemical change used for cleaning?
Removing stains on clothes with bleach.
What color change occurs when water is added to anhydrous copper(II) sulfate?
It turns from white to blue.
What are some examples of substances we need from Earth?
Clothes, food, medicines, etc.
What is matter?
Anything that occupies space and has mass.
From where can we obtain different substances?
The atmosphere, the ocean, and the Earth's crust.
What will be learned in the topic 'Planet Earth'?
The kinds of substances that humans can extract and methods for obtaining chemicals from various sources.
Is air a pure substance?
No, air is a mixture of gases.
How is matter classified?
Into mixtures and pure substances.
What are examples of pure substances found in air?
Nitrogen, oxygen, and carbon dioxide.
What is an element?
A pure substance that cannot be broken down into anything simpler by chemical methods.
What defines an impure substance?
An impure substance is always a mixture.
What is planet Earth considered as a source of?
A major source of chemicals needed for living standards.
