Elements, Mixtures, Compounds Worksheet.pdf - DAAScience10 - Free Printable

Problem Analysis and Solution

The provided image contains several questions related to elements, compounds, and mixtures. Below is a detailed explanation and solution for each question.

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#### Q1: Sea Water
Sea water is a mixture of water and various dissolved substances, such as sodium chloride (table salt). Water is a compound of hydrogen and oxygen. Tick the correct boxes to show whether these statements are true or false.

##### Statements:
1. a) The substances in sea water are not chemically bonded to each other.
- True: Sea water is a mixture, meaning its components (water, sodium chloride, etc.) are physically mixed but not chemically bonded. Each substance retains its individual chemical identity.

2. b) Water can be separated into hydrogen and oxygen by boiling it.
- False: Boiling water separates liquid water from vapor (evaporation), but it does not break the chemical bonds between hydrogen and oxygen atoms. To separate water into hydrogen and oxygen, electrolysis (not boiling) is required.

3. c) When sea water is heated until all the water evaporates, the only thing that is left behind is table salt.
- True: Sea water contains dissolved salts (e.g., sodium chloride) along with water. When water evaporates upon heating, the dissolved salts remain as solids, leaving behind table salt (sodium chloride).

4. d) The formula for water is H₂O because it contains molecules made up of two hydrogen atoms joined to one oxygen atom.
- True: The chemical formula H₂O indicates that each molecule of water consists of two hydrogen atoms covalently bonded to one oxygen atom.

##### Correct Answers:
- a) True
- b) False
- c) True
- d) True

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#### Q2: Filling in the Blanks
Choose from these words to fill in the blanks. Some words may be used more than once.

Words:
compounds, different, bonds, identical, separate

Sentences:
1. Chemicals made up of two or more different elements are called compounds.
- Explanation: Compounds are substances formed when two or more different elements are chemically bonded together.

2. They are usually very difficult to separate using physical methods.
- Explanation: Since compounds are held together by strong chemical bonds, they cannot be easily separated into their constituent elements using physical methods like filtration or distillation.

3. The properties of compounds are different to those of the elements used to make them.
- Explanation: Compounds exhibit properties that are distinct from the properties of their constituent elements. For example, water (H₂O) has different properties than hydrogen and oxygen gases.

4. Mixtures are usually easier to separate because there are no chemical bonds between their different parts.
- Explanation: Mixtures consist of physically combined substances, so they can often be separated using physical methods (e.g., filtration, distillation). There are no chemical bonds holding the components together.

##### Filled-in Sentences:
- Chemicals made up of two or more different elements are called compounds.
- They are usually very difficult to separate using physical methods.
- The properties of compounds are different to those of the elements used to make them.
- Mixtures are usually easier to separate because there are no chemical bonds between their different parts.

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#### Q3: Circle the Substances That Contain Only One Element
Look at these diagrams of substances. Circle the bases that contain only one element.

##### Diagrams:
- Copper: Shows only copper atoms (Cu).
- Oxygen: Shows only oxygen molecules (O₂).
- Water: Shows water molecules (H₂O), which contain both hydrogen and oxygen atoms.
- Ethane: Shows ethane molecules (C₂H₆), which contain both carbon and hydrogen atoms.

##### Analysis:
- Copper: Contains only copper atoms (Cu). It is an element.
- Oxygen: Contains only oxygen molecules (O₂). It is an element (diatomic molecule).
- Water: Contains both hydrogen and oxygen atoms (H₂O). It is a compound.
- Ethane: Contains both carbon and hydrogen atoms (C₂H₆). It is a compound.

##### Substances with Only One Element:
- Copper
- Oxygen

##### Answer:
Circle copper and oxygen.

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#### Q4: Elements in Everyday Substances
Many everyday substances, such as gold and aluminum, are elements. Other substances such as water and sugar are not. Explain what this means in terms of the atoms in these substances.

##### Explanation:
- Elements: Substances composed of only one type of atom. Examples include:
- Gold (Au): Every atom in gold is a gold atom.
- Aluminum (Al): Every atom in aluminum is an aluminum atom.
- Compounds: Substances composed of two or more different types of atoms bonded together. Examples include:
- Water (H₂O): Each molecule of water consists of two hydrogen atoms and one oxygen atom.
- Sugar (C₁₂H₂₂O₁₁): Sugar is composed of carbon, hydrogen, and oxygen atoms bonded together in a specific ratio.

##### Key Difference:
- Elements have atoms of only one type.
- Compounds have atoms of different types bonded together.

##### Answer:
In elements like gold and aluminum, all the atoms are of the same type. In compounds like water and sugar, the substances are made up of atoms of different elements bonded together.

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Final Answers:

1. Q1:
- a) True
- b) False
- c) True
- d) True

2. Q2:
- Chemicals made up of two or more different elements are called compounds.
- They are usually very difficult to separate using physical methods.
- The properties of compounds are different to those of the elements used to make them.
- Mixtures are usually easier to separate because there are no chemical bonds between their different parts.

3. Q3:
- Circle copper and oxygen.

4. Q4:
- In elements like gold and aluminum, all the atoms are of the same type. In compounds like water and sugar, the substances are made up of atoms of different elements bonded together.

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Final Boxed Answer:
\[
\boxed{
\text{Q1: a) True, b) False, c) True, d) True; Q2: compounds, separate, different, bonds; Q3: Copper, Oxygen; Q4: Explanation provided above.}
}
\]