Chemists classify matter as either mixtures or pure substances. Mixtures are combinations of two or more substances that are not chemically bonded and can be separated by physical means. Pure substances are either elements, which cannot be broken down further, or compounds, which are combinations of two or more elements that are chemically bonded. Various separation techniques can be used to separate mixtures based on differences in their physical properties such as density, boiling point, and solubility. These include filtration, crystallization, magnetic separation, distillation, and decantation. Dalton's atomic theory proposed that all matter is composed of indivisible atoms and that atoms of different elements have different properties. Chemical reactions involve the combination and rearrangement of atoms rather than
The document discusses gases and gas laws. It explains that temperature is a measure of how fast gas particles are moving, with higher temperatures meaning faster movement. It introduces the concepts of absolute zero as the coldest possible temperature when particles stop moving, and the Kelvin scale used to measure temperature. The document then explains Boyle's law about the inverse relationship between pressure and volume of a gas at constant temperature. It also discusses Charles' law of the direct relationship between volume and temperature when pressure is constant, and Gay-Lussac's law of the direct relationship between pressure and temperature at constant volume. Several example problems demonstrate applying these gas laws.
Chemists classify matter as either mixtures or pure substances. Mixtures are combinations of two or more substances that are not chemically bonded and can be separated by physical means. Pure substances are either elements, which cannot be broken down further, or compounds, which are combinations of two or more elements that are chemically bonded. Various separation techniques can be used to separate mixtures based on differences in their physical properties such as density, boiling point, and solubility. These include filtration, crystallization, magnetic separation, distillation, and decantation. Dalton's atomic theory proposed that all matter is composed of indivisible atoms and that atoms of different elements have different properties. Chemical reactions involve the combination and rearrangement of atoms rather than
The document discusses gases and gas laws. It explains that temperature is a measure of how fast gas particles are moving, with higher temperatures meaning faster movement. It introduces the concepts of absolute zero as the coldest possible temperature when particles stop moving, and the Kelvin scale used to measure temperature. The document then explains Boyle's law about the inverse relationship between pressure and volume of a gas at constant temperature. It also discusses Charles' law of the direct relationship between volume and temperature when pressure is constant, and Gay-Lussac's law of the direct relationship between pressure and temperature at constant volume. Several example problems demonstrate applying these gas laws.
1. 6.3 INTRODUCCIÓ AL CONCEPTE DE MOL
Un cop definit el concepte de molècula (unitat anterior) com l’agrupació
mínima d’àtoms que representa un compost, vàrem veure que en podíem
calcular la seva massa molecular
La unitat de massa atòmica és massa petita per poder-la utilitzar en
la pràctica. No es pot mesurar en una balança la massa d’un àtom.
Per això necessitem un factor que ens permeti passar de massa
atòmica a una unitat pràctica que es pugui mesurar.necessitem una
unitat de quantitat de matèria.
Aquesta unitat es denomina MOL
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2. Què és un mol? pàgina 139 del llibre de text
Un mol és la quantitat de matèria que conté 6,022x1023 partícules
6,022x1023 és el número d’Avogadro
exemple: un mol de diferents elements:
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3. La massa molar és la massa molecular expressada en grams
Exemple:
La massa d’una molècula de CO és 28 uma
La massa d’un mol de CO és 28 grams
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4. Per què és tan important el mol?
El mol és una de les unitats fonamentals en el sistema internacional (SI) i
probablement la unitat més característica en química, ja que és molt util
perque ens permet comptar el nombre d’àtoms o molècules que hi ha
en una determianda massa de substància.
Això és bàsic ja que les substàncies reaccionen amb unes proporcions
definides.
Per exemple, 2 molècules d’hidrogen reaccionen amb una molècula d’oxigen
per produir dues molècules d’aigua
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5. Així, sempre que volem obtenir aigua amb aquesta reacció, el
nombre de molècules d’hidrogen ha de ser el doble que les
d’oxigen.
Però això com ho podem quantificar? Per això utilitzam el mol.
Un mol d’hidrogen conté el mateix nombre de molècules que un mol
d’oxigen i sabem que hi ha d’haver el doble de partícules d’hidrogen
que d’oxigen.
Així, podem dir que 2 mols d’hidrogen reaccionen amb un d’oxigen
per produir-ne dos d’aigua
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