Additional science revision

Physics P2 revision

• https://www.youtube.com/watch?v=Tmi-kvvXx70 (Einbetten)

Chemistry C2 revision

• https://www.youtube.com/watch?v=k0r6wVbFZOs (Einbetten)

Forces and their effects

• terminal velocity
• An object falling will initially accelerate because of the force due to gravity.
• Eventually the resultant force will be zero as the weight and resistive forces balance.
• The object will then travel at a steady speed which is called its terminal velocity.

The structure of substances

• Ionic compounds
• Giant structures of ions.
• They are held together by strong forces of attraction that act in all directions between oppositely charged ions. this is called ionic bonding.
• Ionic compounds:
• have a high melting an boiling point
• conduct electricity when molten or in solution as the ions are able to move freely.
• Ionic bonds
• An ionic bond occurs between a metal and a non metal. It involves a transfer of electrons from one atom to another.
• This forms electrically charged ions, which all have a completed outer energy level.

The structure of substances

• Alkali metals and halogens
• Alkali metals:
• 1 electron in their outer shell
• react with non metal elements to form ionic compounds where the metal ion has a single positive charge.
• Halogens:
• seven electrons in their outer shell
• react with alkali metals to form an ionic compound where the ions have a single negative charge.
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The structure of substances

• Mixtures and compounds
• A mixture is two or more elements of compounds that aren't chemically combined.
• A compound is a substance where two or more elements are chemically combined.
• Atoms can form chemical bonds by sharing electrons or gaining or losing electrons.
• Simple molecular compounds
• Substances that consist of simple molecular compounds are gases, liquids or solids that have a relatively low melting or boiling point.
• The molecules have no overall electrical charge, so they cant conduct electricity. They have weak intermolecular forces.