Explanation:
Energy makes molecules in the air move faster and expand, decreasing density. The opposite is true for cold air. Molecules are closer together, and absorb less energy.
Answer: OH−.
Explanation: Hydroxide, any chemical compound containing one or more groups, each comprising one atom each of oxygen and hydrogen bonded together and functioning as the negatively charged ion OH-.
Answer:

Explanation:
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In this case, since this is a system in which the water is heated up and the metal is cooled down in a calorimeter which is not affected by the heat lose-gain process, we can infer that the heat lost by the metal is gained be water, it means that we can write:

Thus, in terms of masses, specific heats and temperatures we can write:

Whereas the equilibrium temperature is the given final temperature of 28.4 °C and we can compute the specific heat of the metal as shown below:

Plugging the values in and since the density of water is 1.00 g/mL so the mass is 80.0g, we obtain:

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Assuming the question is asking for percent composition by mass,
The molar mass of sodium bicarbonate is:
22.990 + 1.008 + 12.011 + 3*15.999 = 84.006 g/mol
The molar mass of 3 oxygen atoms is:
3*15.999 = 47.997 g/mol
The percentage composition by mass is:
47.997/84.006 * 100% = 57.1% (3 s.f.)
Answer:
For example, when we bake a cake, it's a result of a mixture of eggs, flour, sugar, and other ingredients. Any time two or more items are combined, a mixture is formed. Sometimes, the different parts of a mixture can be separated into individual entities. Other times, they're married for as long as they exist.
Explanation: