Elements, compounds and mixtures

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Elements

An element is made from only one type of atom.
There are over 100 known elements, listed on the periodic table.
Examples: argon (monatomic gas – single atoms not joined), oxygen (diatomic gas – two atoms chemically joined).

Compounds

A compound is a substance where two or more different atoms are chemically joined.
Example: carbon dioxide contains carbon and oxygen atoms bonded together.
Compounds have different properties from their constituent elements.

Mixtures

A mixture contains two or more elements or compounds that are not chemically joined.
Components can be separated by physical methods.
Examples: nitrogen gas mixed with oxygen gas (mixture of elements); carbon dioxide mixed with carbon monoxide (mixture of compounds).

Key Differences

Element vs compound: element has one type of atom; compound has two or more types chemically joined.
Compound vs mixture: in a compound, atoms are chemically bonded; in a mixture, substances are not chemically joined and can be separated physically.
A mixture can contain elements, compounds, or both.

Identifying Elements, Compounds, and Mixtures from Diagrams

Element: only one type of atom (same colour/size spheres).
Compound: two or more different atoms chemically joined (different spheres bonded together).
Mixture: two or more different atoms or molecules not bonded (different spheres or groups mixed but not joined).

Examples of Elements and Compounds

Elements: iron, nitrogen, oxygen, aluminium.
Compounds: iron oxide (iron + oxygen), carbon dioxide (carbon + oxygen), hydrochloric acid (hydrogen + chlorine), water (hydrogen + oxygen).

Atomic structure of oxygen (element). Two oxygen atoms bond to form O₂ (diatomic element).

Atomic structure of argon (monatomic element).

Particle arrangement in solids, liquids, and gases – useful for understanding mixtures of different states.

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1.Which of the following best describes an element?
Easy
- AA substance made from only one type of atom
- BA substance made from two or more different types of atom chemically joined
- CA substance containing two or more elements or compounds that are not chemically joined
- DA substance that can be separated by physical methods
2.What is a compound?
Easy
- AA substance where two or more atoms of different elements are chemically joined
- BA substance containing only one type of atom
- CA substance where two or more elements are mixed but not chemically joined
- DA substance that consists of only molecules
3.Which of the following is a mixture?
Easy
- AOxygen gas (O₂)
- BCarbon dioxide (CO₂)
- CAir (a mixture of gases)
- DWater (H₂O)
4.Which of the following substances is an element?
Easy
- AIron oxide
- BNitrogen
- CCarbon dioxide
- DWater
5.Which of the following is a compound?
Easy
- AOxygen
- BArgon
- CHydrochloric acid
- DNitrogen gas mixed with oxygen gas
6.What is the difference between an element and a compound?
Medium
- AAn element contains only one type of atom, while a compound contains two or more different types of atom chemically joined
- BAn element can be separated by physical methods, while a compound cannot
- CAn element is always a gas, while a compound is always a solid
- DAn element contains molecules, while a compound contains atoms
7.Which statement correctly describes the difference between a compound and a mixture?
Medium
- AIn a compound, different substances are chemically joined; in a mixture, they are not chemically joined
- BIn a compound, substances are physically combined; in a mixture, they are chemically combined
- CA compound can be separated by filtration, but a mixture cannot
- DA mixture always contains elements only, while a compound contains compounds only
8.Which of the following diagrams represents an element? (Assume different shapes represent different types of atoms)
Easy
- AA diagram showing only one type of atom (e.g., all circles the same)
- BA diagram showing two different types of atoms bonded together
- CA diagram showing two different types of atoms not bonded together
- DA diagram showing many different types of atoms all bonded

Thêm câu hỏi

9.Which of the following is a mixture of compounds?
Medium
- ACarbon dioxide mixed with carbon monoxide
- BOxygen gas
- CIron oxide
- DNitrogen gas
10.A substance contains two different types of atoms that are not chemically joined. What is it?
Easy
- AA mixture of elements
- BA compound
- CAn element
- DA mixture of compounds
11.Which of the following statements is true about diatomic elements?
Medium
- AThey exist as molecules containing two atoms chemically joined
- BThey contain only single atoms that are not chemically joined
- CThey are always compounds
- DThey cannot be elements
12.A student has a sample of a substance. They observe that it can be separated into different components by physical means. Which type of substance is it?
Easy
- AA mixture
- BA compound
- CAn element
- DA diatomic element
13.A student has a sample of a gas. They find that it cannot be broken down into simpler substances by chemical means, and it consists of only one type of atom. What is the sample?
Easy
- AAn element
- BA compound
- CA mixture
- DA diatomic molecule
14.Which of the following statements about a compound is correct?
Easy
- AIt contains two or more elements chemically joined together.
- BIt contains two or more elements not chemically joined.
- CIt contains only one type of atom.
- DIt can be separated by physical methods.
15.A substance is found to be made up of two different types of atoms that are chemically bonded. Which type of substance is it?
Easy
- AA compound
- BA mixture
- CAn element
- DA diatomic element
16.A student has two samples: Sample X is a liquid that boils at 78°C, and Sample Y is a liquid that boils at 100°C. When they mix the two liquids, the mixture boils over a range of temperatures from 80°C to 95°C. What does this indicate about the mixture?
Medium
- AIt is a mixture of two compounds.
- BIt is a compound formed from the two liquids.
- CIt is a mixture of two elements.
- DIt is a pure substance.
17.The diagram shows the particle arrangement of a substance. Which type of substance is represented?
Easy
- AA mixture of elements
- BA compound
- CAn element
- DA mixture of compounds
18.A substance contains only one type of atom. Which of the following is true?
Easy
- AIt is an element.
- BIt is a compound.
- CIt is a mixture.
- DIt must be a gas.
19.A sample of a substance is found to have a fixed composition and can be separated into its components by chemical methods only. What type of substance is it?
Medium
- AA compound
- BA mixture
- CAn element
- DA solution
20.A student is given four samples: W, X, Y, Z. W is a liquid that evaporates completely leaving no residue. X is a liquid that leaves a white solid after evaporation. Y is a gas that burns with a pop. Z is a gas that relights a glowing splint. Which two samples are likely to be pure substances?
Medium
- AW and Y
- BX and Z
- CW and Z
- DX and Y
21.A student heats a green powder. It turns black and a gas is released that turns limewater milky. The mass of the black solid is less than the original green powder. Which statement is correct?
Medium
- AThe green powder was a compound.
- BThe green powder was an element.
- CThe green powder was a mixture.
- DThe green powder was a diatomic element.
22.A student heats a green powder. It turns black and a gas is released that turns limewater milky. The mass of the black solid is less than the original green powder. Which of the following best explains the decrease in mass?
Medium
- AA gas was produced and escaped into the air.
- BThe solid evaporated.
- CThe solid contracted as it cooled.
- DThe green powder was a mixture and the black solid is an element.
23.A student has four samples: W, X, Y, Z. W is a liquid that evaporates completely leaving no residue. X is a liquid that leaves a white solid after evaporation. Y is a gas that burns with a pop. Z is a gas that relights a glowing splint. Which of the following is most likely a mixture?
Medium
- AW
- BX
- CY
- DZ
24.A student measures the boiling point of a liquid. It starts boiling at 78°C but the temperature gradually rises to 100°C as boiling continues. Which of the following is the best conclusion?
Medium
- AThe liquid is a pure substance.
- BThe liquid is a mixture of two or more liquids.
- CThe liquid is an element.
- DThe thermometer is faulty.
25.Which of the following techniques would be best to separate a mixture of iron filings and sand?
Easy
- AFiltration
- BEvaporation
- CUsing a magnet
- DDistillation
26.A student adds a few drops of iodine solution to a sample of food. The iodine turns blue-black. Which of the following is the best conclusion?
Easy
- AThe food contains protein.
- BThe food contains starch.
- CThe food contains fat.
- DThe food contains sugar.
27.A student has a colourless liquid. They add anhydrous copper sulfate, which turns blue. Then they add a small piece of sodium metal, which fizzes and produces a gas that burns with a pop. Which of the following is the liquid?
Hard
- APure water
- BDilute hydrochloric acid
- CEthanol
- DSalt water
28.A student wants to separate a mixture of sand and salt. Which of the following sequences of techniques is correct?
Medium
- AFiltration then evaporation
- BEvaporation then filtration
- CDistillation then condensation
- DChromatography then filtration
29.A student performs a chromatography experiment on a black ink. The chromatogram shows three spots: one red, one blue, and one yellow. Which of the following is true?
Medium
- AThe black ink is an element.
- BThe black ink is a compound.
- CThe black ink is a mixture of three dyes.
- DThe black ink is a pure substance.
30.Which of the following is a chemical change?
Easy
- ADissolving sugar in water
- BMelting ice
- CBurning wood
- DCutting paper
31.A student adds a few drops of Benedict's solution to a sample and heats it. The solution turns from blue to brick red. Which of the following is present?
Easy
- AStarch
- BProtein
- CFat
- DReducing sugar
32.A student has two colourless liquids: liquid A and liquid B. Liquid A has a pH of 2. Liquid B has a pH of 12. They mix equal volumes of A and B. The resulting mixture has a pH of 7. Which of the following is the best conclusion?
Medium
- ABoth liquids are pure water.
- BLiquid A is an acid, liquid B is a base, and they neutralised each other.
- CLiquid A is a base, liquid B is an acid.
- DThe mixture is still acidic.
33.The diagram shows the particle arrangement of a substance. Which type of substance is represented? (Assume circles represent atoms, different colours represent different elements, and bonds are shown where atoms are joined.)
Medium
- AAn element
- BA compound
- CA mixture of elements
- DA mixture of compounds
34.Which of the following is an element?
Easy
- AArgon
- BWater
- CCarbon dioxide
- DHydrochloric acid
35.Which of the following substances is a diatomic element?
Easy
- AArgon
- BOxygen
- CCarbon
- DIron
36.A substance contains two different types of atoms that are chemically joined. What is it?
Easy
- AAn element
- BA compound
- CA mixture
- DA monatomic gas
37.Which of the following statements is correct?
Medium
- AA mixture has a fixed composition.
- BA compound can be separated by physical methods.
- CAn element contains more than one type of atom.
- DA compound contains atoms of different elements chemically joined.
38.Which of the following lists contains only compounds?
Medium
- AIron, Nitrogen, Oxygen
- BWater, Carbon dioxide, Hydrochloric acid
- CArgon, Aluminium, Iron oxide
- DNitrogen oxide, Oxygen, Carbon
39.How many types of atoms are present in a sample of carbon dioxide?
Easy
- A1
- B2
- C3
- D4
40.Which of the following describes a mixture of compounds?
Medium
- ACarbon dioxide mixed with carbon monoxide
- BNitrogen gas mixed with oxygen gas
- CIron oxide (Fe2O3)
- DArgon gas
41.Which of the following is the best definition of an element?
Easy
- AA substance made from only one type of atom
- BA substance made from two or more types of atom chemically joined
- CA substance made from two or more types of atom not chemically joined
- DA substance that can be separated by physical methods
42.A compound contains atoms of different elements that are chemically joined together.
Easy
True or false?
43.A mixture can be separated into its components by chemical methods only.
Easy
True or false?
44.Which of the following substances is a compound?
Easy
- AOxygen gas
- BIron
- CCarbon dioxide
- DNitrogen gas
45.How many types of atoms are present in a sample of pure water (H₂O)?
Easy
- A1
- B2
- C3
- D4
46.The diagram below shows the particle arrangement of a substance. Each circle represents an atom. Which type of substance is represented? (Different colours represent different elements)
Medium
- AAn element
- BA compound
- CA mixture of elements
- DA mixture of compounds
47.Match each substance to its correct classification.
Medium
- Oxygen gas
- Carbon dioxide
- Air
- Element
- Compound
- Mixture
48.Arrange the following in order of increasing complexity: compound, element, mixture.
Easy
- Compound
- Element
- Mixture
49.Which of the following are elements? (Select all that apply)
Easy
- AOxygen
- BWater
- CIron
- DCarbon dioxide
50.Which of the following diagrams represents a compound? (Assume different shapes represent different types of atoms)
Medium
- AA diagram with only one type of atom (e.g., all circles)
- BA diagram with two different types of atoms that are not touching
- CA diagram with two different types of atoms that are touching (bonded)
- DA diagram with three different types of atoms all separate
51.Complete the sentence:
Easy
A substance that contains two or more elements or compounds that are not chemically joined is called a ____.
52.State one difference between a compound and a mixture.
Medium
53.Complete the sentence: A compound contains atoms of different elements that are ___ joined.
Easy
A compound contains atoms of different elements that are ____ joined.
54.Describe what an element is. Give an example.
Medium

Ghi chú ôn tập

## Elements, Compounds & Mixtures - **Element**: made from only **one type of atom**. Listed on the periodic table (over 100 known). Examples: argon (monatomic gas), oxygen (diatomic gas). - **Compound**: two or more atoms of **different elements** chemically joined. Example: carbon dioxide (contains carbon and oxygen). - **Mixture**: contains two or more elements or compounds **not chemically joined**. Example: nitrogen gas mixed with oxygen gas (mixture of elements); carbon dioxide mixed with carbon monoxide (mixture of compounds). ### Key Differences - **Element vs Compound**: Element has one type of atom; compound has two or more different atoms chemically bonded. - **Compound vs Mixture**: In a compound, atoms are chemically joined; in a mixture, substances are not chemically joined and can be separated by physical means. ### Examples from Workbook - **Elements**: Iron, Nitrogen, Oxygen, Aluminium - **Compounds**: Iron Oxide, Carbon dioxide, Hydrochloric acid, Water - Compounds contain: Iron oxide (iron, oxygen); Carbon dioxide (carbon, oxygen); Hydrochloric acid (hydrogen, chlorine); Water (hydrogen, oxygen). ### Quick Check - Diatomic gas: two atoms chemically joined (e.g., O₂). - Monatomic gas: single atoms not joined (e.g., Ar).

Element: A substance made from only one type of atom.
Compound: A substance where two or more atoms of different elements are chemically joined.
Mixture: A substance that contains two or more elements or compounds that are not chemically joined together.
Diatomic gas: A gas that contains two atoms that are chemically joined (e.g., oxygen).
Monatomic gas: A gas that contains only single atoms that are not chemically joined (e.g., argon).

Thẻ ghi nhớ

What is an element?

An element is made from only one type of atom. There are over 100 known elements listed on the periodic table.

What is a compound?

A compound is a substance where two or more atoms of different elements are chemically joined together.

What is a mixture?

A mixture is a substance that contains two or more elements or compounds that are not chemically joined together.

What is a diatomic gas?

A diatomic gas contains two atoms that are chemically joined, e.g., oxygen (O₂).

What is a monatomic gas?

A monatomic gas contains only single atoms that are not chemically joined, e.g., argon (Ar).

Is oxygen an element, compound, or mixture?

Oxygen is an element because it contains only one type of atom.

Is carbon dioxide an element, compound, or mixture?

Carbon dioxide is a compound because it contains atoms of carbon and oxygen chemically joined.

Is a mixture of nitrogen and oxygen an element, compound, or mixture?

It is a mixture of two different elements (nitrogen and oxygen) that are not chemically joined.

Is argon an element, compound, or mixture?

Argon is an element because it contains only one type of atom.

List the elements from: iron, iron oxide, nitrogen, oxygen, carbon dioxide, aluminium, hydrochloric acid, water.

Elements: iron, nitrogen, oxygen, aluminium.

List the compounds from: iron, iron oxide, nitrogen, oxygen, carbon dioxide, aluminium, hydrochloric acid, water.

Compounds: iron oxide, carbon dioxide, hydrochloric acid, water.

What elements does iron oxide contain?

Iron oxide contains iron and oxygen.

What elements does carbon dioxide contain?

Carbon dioxide contains carbon and oxygen.

What elements does hydrochloric acid contain?

Hydrochloric acid contains hydrogen and chlorine.

What elements does water contain?

Water contains hydrogen and oxygen.

Describe the difference between an element and a compound.

An element contains only one type of atom, while a compound contains two or more different types of atoms chemically joined.

Describe the difference between a compound and a mixture.

In a compound, atoms of different elements are chemically joined; in a mixture, substances are not chemically joined and can be separated by physical means.

How many known elements are there?

There are over 100 known elements.

Where are elements listed?

Elements are listed on the periodic table.

Give an example of a mixture of compounds.

Carbon dioxide mixed with carbon monoxide is a mixture of compounds.

Give an example of a mixture of elements.

Nitrogen gas mixed with oxygen gas is a mixture of elements.

What is the key difference between a diatomic and monatomic gas?

A diatomic gas has two atoms chemically joined; a monatomic gas has single atoms not chemically joined.

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