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General Biology: Chemical Context of Life

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이 집합의 용어 (20)

  • What is matter?

    Matter is anything that takes up space and has mass, including rocks, metals, oils, gases, and living organisms.

  • What is an element?

    An element is a substance that cannot be broken down into other substances by chemical reactions and consists of one type of atom.

  • How many natural elements are recognized by chemists?

    Chemists recognize 92 natural elements occurring in nature.

  • What is a compound?

    A compound is a substance made of two or more different elements combined in a fixed ratio with properties different from its elements.

  • Give an example of a compound and its elements.

    Table salt (sodium chloride, NaCl) is a compound of sodium (Na) and chlorine (Cl) in a 1:1 ratio.

  • What are the four elements that make up approximately 96% of living matter?

    Oxygen (O), carbon (C), hydrogen (H), and nitrogen (N) make up about 96% of living matter.

  • What are trace elements?

    Trace elements are elements required by organisms in minute quantities, such as iron (Fe) and iodine (I).

  • Why is iodine important for vertebrates?

    Iodine (I) is essential for producing a hormone by the thyroid gland; a daily intake of 0.15 mg is adequate for normal thyroid activity.

  • What is an atom?

    An atom is the smallest unit of matter that retains the properties of an element.

  • How do atoms relate to elements?

    Each element consists of atoms unique to that element, symbolized by the element's abbreviation (e.g., C for carbon).

  • What determines an element's properties?

    An element's properties depend on the structure of its atoms, including the arrangement of electrons.

  • What is the significance of valence electrons?

    Valence electrons determine an atom's ability to form chemical bonds.

  • How many bonds can oxygen form and why?

    Oxygen can form two bonds because it has space for two more electrons in its outer shell.

  • What are emergent properties of compounds?

    Emergent properties mean a compound has characteristics different from those of its individual elements.

  • Why is sodium chloride edible despite its elements being toxic separately?

    When sodium and chlorine chemically combine, they form sodium chloride, an edible compound unlike its toxic elements.

  • What is the role of electronegativity in chemical bonds?

    Electronegativity affects how atoms attract electrons in bonds, influencing molecule polarity and reactivity.

  • What is an example of a toxic element and its impact?

    Arsenic is toxic to humans and linked to diseases; it can contaminate groundwater in some regions.

  • How have some plants adapted to toxic elements in soil?

    Some plants have evolved to survive in soils with toxic elements like chromium and nickel, such as those in serpentine soils.

  • What percentage of the human body mass is oxygen?

    Oxygen makes up approximately 65.0% of human body mass.

  • Name three essential elements besides O, C, H, and N that make up the remaining body mass.

    Calcium (Ca), phosphorus (P), and potassium (K) are essential elements making up most of the remaining ~4% of body mass.