Before we discuss how substances change, let’s talk about how we identify them. Substances have physical and chemical properties, or traits. You can use those traits to identify a substance. A substance’s physical properties include its shape, volume and freezing point. You can measure and observe these properties without changing the composition of a substance. For example, you can freeze liquid water to observe its freezing point without changing what the water is made of. The liquid water would become ice, but each molecule of water still contains two atoms of hydrogen and one of oxygen. A substance’s chemical properties include its pH level, flammability and reactivity with oxygen. You can’t measure these properties unless you also change the way the atoms or molecules are arranged.

In the passage above, what does the “composition” of a substance mean

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.

answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).

the answer is 0.42 is that is an option. this question provides no info

the population of unionid mussels in the hudson river decreased after zebra mussels were introduced. zebra mussels, a nonnative species, competed with the unionid mussels for food. the zebra mussels were able to outcompete the unionid mussels, allowing the zebra mussel population to increase dramatically over six years. the unionid mussel population decreased due to a lack of food.

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