Chemical Changes

Question 1

What is a chemical change?

Answer 1

A chemical change changes the nature and characteristic properties of matter. It produces 1 or more new substances.

Question 2

What is the law of conservation of mass?

Answer 2

The law is that nothing is lost, nothing is created, all is transformed. You must have the same amount of atoms on each side

Question 3

chemical changes are expressed in an equation. There are reactants on the left, products on the right. How can we know if a chemical change has occurred?

Answer 3

Clues:
The release of gas
changes of heat 
Generation of light
Change of colour
Formation of a precipitate

Question 4

What is synthesis?

Answer 4

Synthesis is forming a complex molecule from atoms or simple molecules

Question 5

When energy in the equation is with the reactants, it is…

Answer 5

Absorbing energy

Question 6

When energy is on the products side in an equation, it is…

Answer 6

Releasing energy

Question 7

What types of synthetic reactions take place in living beings?

Answer 7

Photosynthesis and cellular respiration

Question 8

What is decomposition?

Answer 8

Decomposition is the transformation of complex molecules into simple molecules. It is the opposite of synthesis. It makes a complex molecule into a simple molecule, while synthesis makes a simple molecule into a complex molecule

Question 9

What happens at the end of decomposition?

Answer 9

The energy that was stored in the molecule is released and transformed into other types of energy

Question 10

What is oxidation?

Answer 10

Oxidation is a chemical reaction involving oxygen or substance that has similar properties to oxygen like oxygen sulfur and chlorine

Question 11

What’s an example of oxidation?

Answer 11

The formation of rust on metal.

Question 12

Can only metal oxidize?

Answer 12

No

Question 13

What is the role of energy in oxidation reactions?

Answer 13

Releasing energy but slowly

Question 14

What is the difference between cellular respiration and photosynthesis?

Answer 14

Cellular respiration releases energy, but photosynthesis absorbs energy

Question 15

What’s precipitation?

Answer 15

Precipitation is the formation of a solid (that is less soluble or not soluble) following the mixing of two solutions.
Ex: vinegar and milk
Precipitation is used as separation techniques for certain mixtures

Equation: KI + Pb(NO3)2—

Question 16

What’s the role of energy in synthesis?

Answer 16

• It either absorbs or releases energy.

Question 17

What’s the role of energy in decomposition?

Answer 17

The chemical energy in a molecule is usually released and transformed into another energy.
Decomposition always involves the release of energy in living organisms.

Question 18

What’s the role of energy in oxidation?

Answer 18

• It releases energy, but in slow oxidation it’s hard to see
• combustion is an exothermic reaction, and it releases energy because it’s fast
• fire breathes oxygen

Question 19

An example of oxidation is combustion. What is combustion?

Answer 19

It’s heat + fuel + oxygen = rapid reaction and release of energy.

It happens in our bodies: In our body, oxidation occurs. Glucose from what we eat reacts with the oxygen we breathe to give the energy to our bodies to keep warm and move around.

Question 20

What is the formula for cellular respiration?

Answer 20

C6H12O6—