Year 9 Chemistry Flashcards
Physical Change
A physical change involves only a change to the physical property of a substance such as its shape, state or temperature. A physical change can usually be reversed as no new substance is formed.
Chemical Change
With a chemical change, one or more new substances are formed. The change is called a chemical reaction and the new substance(s) has different physical and chemical properties from the old substance.
Example of a physical change
For example, when water freezes to ice its properties change. It is now a solid - but it is still water. And it can be easily changed back to liquid water.
Example of a chemical change
For example, when hydrogen and oxygen react, they bond to form water.
All chemical reactions involve what?
Reactants and products.
Rusting is a chemical reaction in which iron reacts with oxygen in the air to form iron oxide. The reactants are?
Iron and oxygen
How many hydrogen atoms are there in each molecule of ammonia, NH3?
3
Electrical charge of a proton
Positive
Electrical charge of a neutron
Neutral
Electrical charge of a electron
Negative
Which subatomic particle is not found in the nucleus?
Electron
The mass of the neutron is approximately equal to the mass of the?
Proton
Which subatomic particles are found in the nucleus?
Proton and neutron
Most of an atom’s volume is made up of what?
Empty Space
Where is most of the mass of an atom located?
Inside of the nucleus
Overall the nucleus has a _______electrical charge
Positive
What is a chemical element?
A substance made up of only one type of atom
Calcium is an element. What type of atoms is it made out of?
Calcium Atoms
Ammonia is a colourless gas that is used to make fertilizers, cleaners and medicines. A chemist heats up some pure ammonia to very high temperature and finds that it breaks down into two other gases.
Is ammonia an element?
No, because it is made up of multiple types of atoms.
Like helium, argon is a noble gas. What structure would you expect argon to have?
Single Atoms
Phosphorus is an element in which the atoms often bond together in groups of four. What is each group called?
A molecule
T/F? A chemical bond is an attractive force that binds molecules to other molecules.
True
Difference between a mixture and compound
Compounds are substances formed by the chemical combination of two or more elements. Mixtures are substances formed by physically mixing two or more substances together
Endothermic reactions:
Absorb energy, causing a decrease in temperature
Breaking chemical bonds:
Requires energy
Making chemical bonds:
Releases energy
T/F? All chemical reactions absorb energy and release energy.
True
Activation energy is:
Needed to break the bonds in the reactant molecules
Required for both exothermic and endothermic reactions
Activation Energy
The minimum amount of energy that is required to activate atoms or molecules to a condition in which they can undergo chemical transformation or physical transport.
