Unit 2: Matter
Review Questions
1. Encircle the correct answer.
- Anything that has mass and occupies space is called:
(a) Liquid (b) Gas (c) Solid (d) Matter
- Following are states of matter:
(a) Gas (b) Liquid (c) Solid (d) All of these
- Macroscopic properties are properties that can be visualized by:
(a) the naked eye (b) microscope (c) electron microscope (d) telescope
- Matter can be described by both its:
(a) physical properties and chemical properties (b) physical properties
(c) chemical properties
- A substance formed when two or more different elements combine chemically:
(a) atom (b) compound (c) element (d) solution
2. Give short answer.
- Can you write the formula of the carbon dioxide gas that we exhale?
The formula for the carbon dioxide gas that we exhale is CO₂. It consists of one carbon atom and two oxygen atoms.
- Define the element, Compound, Mixture.
Element: A pure substance made of only one type of atom.
Example: Oxygen (O₂).
Compound: A substance formed when two or more different atoms chemically combine. Example: Water (H₂O).
Mixture: A combination of two or more substances that are not chemically bonded. Example: Saltwater (salt mixed with water).
- Differentiate between compound and mixture.
| Compound | Mixture |
| A substance formed when two or more different atoms chemically combine. | A combination of two or more substances that are not chemically bonded |
| Requires chemical processes to separate its components. | Can be separated by physical methods like filtration or evaporation. |
| Water (H2O), Carbon Dioxide (CO2) | Salad, Air, Saltwater |
- Differentiate between concentrated and dilute solution.
| Concentrated Solution | Dilute Solution |
| Contains a large amount of solute relative to the solvent. | Contains a small amount of solute relative to the solvent. |
| Often appears darker or more intense in color. | Often appears lighter or less intense in color. |
| For example, strong coffee, concentrated hydrochloric acid. | For example, weak tea, dilute vinegar |
| Low ratio of solvent to solute. | High ratio of solvent to solute. |
3. Define the term Allotropes. Explain the allotropes of Carbon.
Allotropes:
The property of an element to exist in different physical forms is called allotropy. These different forms in the same physical state are called allotropes.
Three important allotropes of carbon.
Diamond:
Structure: Each carbon atom is tetrahedrally bonded to four other carbon atoms, forming a very rigid and three-dimensional lattice.
Properties: Extremely hard, high melting point, excellent electrical insulator.
Uses: Cutting tools, jewelry.
Graphite:
Structure: Each carbon atom is bonded to three other carbon atoms in a hexagonal arrangement, forming layers that slide over each other easily.
Properties: Soft, slippery, good conductor of electricity, high melting point.
Uses: Lubricant, lead pencil, electrodes, batteries.
Buckyballs (C-60):
Buckyballs, also known as fullerenes, have a football like fused hollow ring structure made up of twenty hexagons and twelve pentagons. Each of its 60 carbon atoms are bonded to 3 carbon atoms.
4. What is difference between Homogeneous and heterogeneous solution?
| Homogeneous Solution | Heterogeneous Solution | ||
| Composition is uniform throughout. | Composition is not uniform. | ||
| Particles are evenly distributed. | Particles are unevenly distributed. | ||
| Consists of a single phase. | Consists of two or more phases. | ||
| Cannot be separated by physical means like filtration. | Can be separated by physical means like filtration. | ||
| Example: Saltwater | Example: Sand in water |
5. Differentiate between the colloids, suspension and solution.
Solution:
- A homogeneous mixture of two or more components
- Particle size is less than 1nm. Not visible by naked eye
- Particles can pass through normal as well as ultra-filter paper
- Cannot Scatter the light (due to small size)
- Does not separate
- Example: Sea water
Colloids:
- A heterogeneous mixture of two or more components
- Particle size vary from 1-103 nm. Visible by naked eye.
- Particles can pass through normal filter paper but not through ultra-filter paper
- Can Scatter the light (Tyndal effect)
- Does not separate
- Example: Milk
Suspension:
- A heterogeneous mixture of two or more components
- Particle size greater than 10 nm. Visible by naked eye by naked eye
- Particles cannot pass through normal as well as ultra-filter paper
- Can Scatter the light (Tyndal effect)
- Separate or settles down when stationary
- Example: Muddy water
6. If there are 18 protons in the Argon atom, then what is the atomic number of Argon?
The atomic number of an element is equal to the number of protons in its atom. Therefore, if there are 18 protons in the Argon atom, the atomic number of Argon is 18.
7. Describe State of matter with example.
There are four primary states of matter:
- Gas
- Liquid
- Solid
- Plasma
Description of States of Matter:
Solid: Particles are tightly packed in a fixed arrangement, resulting in a definite shape and volume. For example, ice is a solid form of water.
Liquid: Particles are close together but not in a fixed arrangement, allowing liquids to take the shape of their container while maintaining a constant volume. For example water.
Gas: Particles are far apart and move freely, allowing gases to fill the entire volume of their container. For example oxygen we breathe.
Plasma: An ionized gas with free electrons, formed at very high temperatures or strong electric fields. For example the sun and fluorescent lights.
Additional States:
Liquid Crystal: Some crystalline solids become cloudy liquids when heated, possessing properties of both liquids and solids within a certain temperature range. Further heating turns them into transparent liquids. For example Cholesteryl Benzoate.
Bose-Einstein Condensates (BEC): Observed under extremely cold temperatures near absolute zero, BECs are states of matter where separate atoms coalesce into a single quantum state. For example superfluid’s and superconductors.
8. Differentiate between the following.
a. Colloids and Suspensions
| Colloids | Suspensions |
| A heterogeneous mixture of two or more components | A heterogeneous mixture of two or more components |
| Particle size vary from 1-103 nm. Visible by naked eye. | Particle size greater than 10 nm. Visible by naked eye by naked eye |
| Particles can pass through normal filter paper but not through ultra-filter paper. | Particles cannot pass through normal as well as ultra-filter paper |
| Can Scatter the light. | Can Scatter the light (Tyndal effect) |
| Does not separate | Separate or settles down when stationary |
| Example: Milk | Example: Muddy water |
b. Elements and Compounds
| Element | Compound | |
| A pure substance made of only one type of atom. | A substance formed when two or more different elements chemically combine. | |
| Oxygen (O2), Gold (Au), Hydrogen (H2) | Water (H2O), Carbon Dioxide (CO2), Sodium Chloride (NaCl) | |
| Consists of only one kind of atom. | Consists of molecules formed by atoms of different elements. |
c. Concentrated and Dilute solutions
| Concentrated Solution | Dilute Solution |
| Contains a large amount of solute relative to the solvent. | Contains a small amount of solute relative to the solvent. |
| Often appears darker or more intense in color. | Often appears lighter or less intense in color. |
| For example, strong coffee, concentrated hydrochloric acid. | For example, weak tea, dilute vinegar |
| Low ratio of solvent to solute. | High ratio of solvent to solute. |
9. Examine the concept of solubility.
Solubility:
Solubility is the maximum amount of solute which dissolves in a specified amount of solvent at a specific temperature. The solubility of a substance depends on the solvent used, as well as temperature and pressure.
Effect of Temperature on Solubility:
The solubility of solutes depends on temperature. Depending on the nature of solute there is either:
a) Increase in solubility with temperature e.g., KCI, NH4CI
b) Decrease in solubility with temperature e.g., Na2SO4, Ca(OH)2
Table: Solubility of Some Salts in Water at Different Temperatures
| Solute | Solubility at 20°C (g/100g H₂O) | Solubility at 100°C (g/100g H₂O) |
| NaCl | 36.5 | 39.2 |
| KCl | 34.7 | 56 |
| NH₄Cl | 37.5 | 77 |
| Ca(OH)₂ | 0.173 | 0.066 |
Graph showing effect of temperature on solubility:
THINK TANK
10. Why is a solution considered mixture?
A solution is a mixture because it combines a solute and a solvent. The solute dissolves in the solvent, creating a uniform blend while each substance keeps its original properties.
11. How will you test weather given solution is a colloid or a solution?
To test whether a given mixture is a colloid or a solution, we can use the Tyndall effect. When a light beam is passed through the mixture:
Solution: The light passes through without scattering, as the particles are too small to scatter light.
Colloid: The light is scattered, and the path of the light beam becomes visible because colloidal particles are large enough to scatter light.