name per date chemistry
writing & classifying mixtures class activity
answer all the questions. use complete sentences and provide examples to support your responses
1. is the following sentence true or false? most samples of matter are mixtures. why/why not?
2. what is a mixture?
3. is the following sentence true or false? a heterogeneous mixture is one that has a completely uniform composition. why/why not
4. what is another name for a homogeneous mixture? describe.
5. circle the letter of the term that describes a part of a sample having uniform composition and properties and provide an explanation for either yes or no.
a. solution why/why not:
b. mixture why/why not:
c. state why/why not:
d. phase why/why not:
6. how many phases exist in these types of mixtures? describe using complete sentences to get full credits.
a. homogeneous
b. heterogeneous
essay writing. use complete sentences to describe the following:
is matter still the same even though it has changed state? how do you know?
can water be all three states? explain.
matter is everything. it has mass and takes up space. explain this.
what type of matter is most suited to build bridges? why?
what type of matter is most absorbent? how do you know?
what type of matter is more suitable to build wheels from? why do you think so?
what types of matter do we eat?
brainstorm all the matter you can think of that is flexible and will bend.
can you think of things that aren’t matter? (e.g. things, sound, thoughts, colors, shadows).

Question

Accepted Answer

1. **Answer**: True. Most samples of matter in our daily - life are mixtures. For example, air is a mixture of nitrogen, oxygen, carbon - dioxide and other gases; ocean water is a mixture of water, salt and various dissolved substances.
   - **Explanation**: In nature and in our surroundings, pure substances are less common compared to mixtures. Many substances we encounter are made up of two or more different components physically combined.
2. **Answer**: A mixture is a physical combination of two or more substances in which the identities of the substances are retained. For example, a mixture of sand and water, or a mixture of iron filings and sulfur powder.
   - **Explanation**: The components of a mixture are not chemically bonded to each other and can be separated by physical means such as filtration, evaporation, or magnetic separation.
3. **Answer**: False. A heterogeneous mixture is one that does not have a completely uniform composition. For example, a mixture of oil and water, or a salad (a mixture of different vegetables).
   - **Explanation**: In a heterogeneous mixture, the different components can be visually distinguished and their distribution is not even throughout the mixture.
4. **Answer**: Another name for a homogeneous mixture is a solution. A homogeneous mixture has a uniform composition throughout. For example, salt - water (sodium chloride dissolved in water) is a solution. The salt is evenly distributed in the water at a molecular level.
   - **Explanation**: In a solution, the solute (the substance being dissolved) is uniformly dispersed in the solvent (the substance doing the dissolving).
5.
   - **a. Answer**: Yes. A solution has a uniform composition and properties. For example, a sugar - water solution has the same sweetness and density throughout.
     - **Explanation**: The solute particles in a solution are evenly distributed at a molecular level.
   - **b. Answer**: No. A general mixture may not have uniform composition. For example, a mixture of sand and gravel has different regions with more sand or more gravel.
     - **Explanation**: Mixtures can be heterogeneous with non - uniform distribution of components.
   - **c. Answer**: No. State (solid, liquid, gas) is a physical property not related to composition uniformity. For example, ice (solid water) is a pure substance in solid state but not all solids are uniform mixtures.
     - **Explanation**: State describes the physical form of a substance, not its compositional uniformity.
   - **d. Answer**: Yes. A phase is a part of a sample with uniform composition and properties. For example, in a glass of ice - water, the ice is one phase and the liquid water is another phase, and each phase has its own uniform properties.
     - **Explanation**: Phases within a system are regions with distinct and uniform characteristics.
6.
   - **a. Answer**: A homogeneous mixture has one phase. For example, a sugar - water solution is a single - phase system as the sugar is uniformly dissolved in water.
     - **Explanation**: There are no distinct boundaries or different regions within the mixture.
   - **b. Answer**: A heterogeneous mixture can have two or more phases. For example, in a mixture of oil and water, the oil forms one phase and the water forms another phase.
     - **Explanation**: The different components in a heterogeneous mixture separate into distinct regions or phases.

For the essay - writing part:
1. **Answer**: Matter is still the same even though it has changed state. For example, when water freezes into ice or evaporates into steam, it is still composed of water molecules (H₂O). We know this because the chemical composition remains unchanged during a physical change of state.
   - **Explanation**: Physical changes like changes in state do not involve breaking or forming of chemical bonds, so the identity of the substance at the molecular level remains the same.
2. **Answer**: Water can be all three states. It is a liquid at room temperature. When cooled below 0°C, it freezes into a solid (ice). When heated above 100°C at standard atmospheric pressure, it evaporates into a gas (steam).
   - **Explanation**: The different states of water are due to changes in the kinetic energy and intermolecular forces of water molecules.
3. **Answer**: Matter is everything that has mass and takes up space. For example, a book has mass and occupies a certain volume on a shelf. Air also has mass (although it is less noticeable) and fills the space in a room.
   - **Explanation**: Mass is a measure of the amount of matter in an object, and volume is the amount of space it occupies.
4. **Answer**: A solid type of matter, such as steel, is most suited to build bridges. Steel has high strength and durability. It can withstand large tensile and compressive forces, which are necessary for supporting the weight of the bridge and the traffic on it.
   - **Explanation**: Solids have a definite shape and volume and can provide the structural integrity required for bridge - building.
5. **Answer**: Porous solids like sponges are most absorbent. We know this because sponges have many small pores that can hold a large amount of liquid. When a sponge is placed in water, the water is drawn into these pores due to capillary action.
   - **Explanation**: The porous structure allows for the storage of large amounts of liquid within the material.
6. **Answer**: Solids like metals are more suitable to build wheels from. Metals like steel or aluminum have high strength and hardness, which are required to support the weight of a vehicle and withstand the friction and pressure during movement. Also, they can be shaped into round wheels with precision.
   - **Explanation**: Solids maintain their shape and can be engineered to have the necessary mechanical properties for wheel - making.
7. **Answer**: We eat many types of matter. For example, carbohydrates like bread, proteins like meat, and fats like butter. These are all different types of matter that provide us with energy and nutrients.
   - **Explanation**: Food is composed of various chemical substances that are essential for our body's functions.
8. **Answer**: Examples of flexible matter include rubber, plastic films, and some fabrics. Rubber bands can be stretched and then return to their original shape. Plastic wrap can be bent and molded around objects.
   - **Explanation**: These materials have molecular structures that allow for some degree of deformation without breaking.
9. **Answer**: Things that aren't matter include sounds, thoughts, colors, and shadows. Sounds are vibrations in the air and do not have mass or take up space. Thoughts are electrical and chemical processes in the brain and are intangible. Colors are perceptions of light and shadows are the absence of light in a region, neither of which have mass or volume.
   - **Explanation**: They do not meet the criteria of having mass and occupying space.

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