Question

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demonstrate understanding

1. explain why the study of chemistry should be important to everyone.
2. define substance and give two examples of things that are substances.
3. explain why there are different branches of chemistry.
4. explain why scientists use mass instead of weight for their measurements.
5. summarize why it is important for chemists to study changes in the world at a submicroscopic level.
6. infer why chemists use models to study submicroscopic matter.
7. identify three models that scientists use, and explain why each model is useful.
8. evaluate how would your mass and weight differ on the moon? the gravitational force of the moon is one - sixth the gravitational force on earth.
9. evaluate if you put a scale in an elevator and weigh yourself as you ascend and then descend, does the scale have the same reading in both instances? explain your answer.
10. distinguish jacques charles described the direct relationship between temperature and volume of all gases at constant pressure. should this be called charles’s law or charles’s theory? explain.

Explanation:

Step1: Define substance

A substance is a form of matter that has a definite composition and distinct properties. Examples of substances are water (H₂O) and sodium chloride (NaCl).

Step2: Branches of chemistry

The main branches include organic chemistry (studies carbon - containing compounds), inorganic chemistry (studies non - carbon compounds), physical chemistry (studies the physical properties and changes of matter), analytical chemistry (studies the separation, identification, and quantification of matter), and biochemistry (studies the chemistry of living organisms).

Step3: Mass vs weight

Mass is a measure of the amount of matter in an object and is constant. Weight is the force exerted on an object due to gravity and can vary depending on the gravitational field. Scientists use mass for measurements because it is an intrinsic property of the object and does not change with location.

Step4: Submicroscopic study

Chemists study changes at the submicroscopic level because the behavior of atoms and molecules determines the properties and reactions of substances. By understanding submicroscopic processes, chemists can predict and control chemical reactions.

Step5: Models in chemistry

Three models are the ball - and - stick model (useful for visualizing the structure and bonding of molecules), the space - filling model (gives a more realistic representation of the size and shape of molecules), and the Lewis structure model (useful for showing the valence electrons and bonding in a molecule).

Step6: Mass and weight on Moon

Mass is the same on the Moon as on Earth because it is an intrinsic property of the object. However, weight is different because the gravitational force on the Moon is about one - sixth of that on Earth. So, an object would weigh less on the Moon but have the same mass.

Step7: Scale in elevator

The scale reading would not be the same. When ascending, the normal force (which the scale measures) is greater than your weight due to the upward acceleration, so the scale reading is higher. When descending, if the elevator is accelerating downward, the normal force is less than your weight and the scale reading is lower.

Step8: Charles's law or theory

This is Charles's law. A law is a statement that summarizes a pattern observed in nature. Charles's statement about the direct relationship between temperature and volume of gases at constant pressure is a well - established pattern based on experimental observations. A theory is a well - supported explanation of why a phenomenon occurs.

Answer:

1. A substance is a form of matter with definite composition and distinct properties. Examples: water, sodium chloride. Branches: organic, inorganic, physical, analytical, biochemistry.
2. Mass is an intrinsic property and constant, while weight depends on gravity and can vary. Scientists use mass for consistent measurements.
3. Studying at the submicroscopic level helps predict and control chemical reactions as atom and molecule behavior determines substance properties.
4. Ball - and - stick (visualize structure and bonding), space - filling (realistic size and shape), Lewis structure (valence electrons and bonding).
5. Mass is the same on the Moon and Earth, but weight is about one - sixth on the Moon due to lower gravitational force.
6. Scale reading is different. Ascending: higher due to upward acceleration. Descending: lower if accelerating downward.
7. It is Charles's law as it is a statement summarizing an observed pattern in nature.