8G ~ elements, mixtures and compounds

Pregunta	Respuesta
What are Elements?	Simple substances that cannot be split up in chemical reactions.
What are the smallest particles of an element that can exist?	Atoms
What does each element have?	Chemical symbols (e.g. O for oxygen)
Where are all the symbols and names for all the known elements are shown?	In the periodic table.
What does a compound contain?	Two or more elements joined together by bonds.
Some elements have their atoms joined to each other in small groups called...?	Molecules
What does the chemical formula of a compound tell you?	The ratio of atoms of each element that are bonded together.
The properties of a compound are...	different from the elements that make it up.
How can chemicals be made to react?	By mixing them with other chemicals, or by using heat or electricity.
What are the 2 ways you can tell that a chemical reaction has occurred?	1. Colour change 2. When a gas is given off
Most chemical reactions also involve an _______ ______. This is usually in the form of ____, for example in burning (combustion).	1+2. Energy change 3. Heat
What is always formed in a chemical reaction? And are they easily reversible?	A new substance and they are irreversible.
How do some chemical reactions take place?	By mixing substances together (e.g. when a solid forms by mixing two liquids in a precipitation reaction).
What do other chemical reactions need to start off?	Energy (e.g. when some compounds are broken up, decomposed, by heat).

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