1) Bubbles forming
2) Energy released or absorbed
3) Formation of a new substance
4) Odor
5) difficult or impossible to reverse
What are signs of a chemical change?
number of atoms in H2O
The oxidation of iron (aka rust) is represented by the equation:
4Fe + 3O2 --> ????
How many atoms must be on the other side of the equation?
What is 10 atoms?
Endothermic reactions feel this way because they have absorbed energy
What is cold?
The full *word* chemical equation for photosynthesis
What is carbon dioxide + water + sunlight energy --> oxygen and glucose?
Boiling water or melting an ice cube is an example of this.
What is a physical change?
number of atoms in glucose, C6H12O6
What is 24?
Which of the following equation is impossible?
a) 2H2 + O2 --> 2H2O
b) Na + Cl --> MgCl
c) CaO + CO2 --> CaCO3
What is b?
Exothermic reactions feel this way because they have released energy
What is hot?
the full word equation for cellular respiration
What is glucose and oxygen create energy, carbon dioxide, and water?
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What is water evaporating or a physical change?
Number AND type of atoms in 2C8ClF15O
What is 50 total:
- 16 Carbon
- 2 Chlorine
- 30 Fluorine
- 2 Oxygen
If you react something on a scale, and the products measure more mass than the reactants, what must be true?
Hint: Think open/closed systems
What is "the system was open"
Exothermic or endothermic:
A bundle of sticks reacts with oxygen to create ash, carbon dioxide gas, and water.
What is exothermic, the bundle of sticks burned and released energy to the air around them
If something is burning, _____ is a reactant.
What is oxygen?
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What is a chemical reaction?
What is something burning/combusting (the products are CO2 and water)?
Number and type of atoms in C8H(NO2)7
What is 30?
8 carbon, 1 H, 7N, 14O
What is always true about the mass of the products in a chemical reaction?
What is the mass always equal the mass of the reactants.
Why is photosynthesis endothermic?
When you light a candle, physical and chemical changes take place. List one of each.
Wax melting = physical
Wick burning = chemical
A student is trying to determine what a clear liquid is. She determines that its density is 0.789 g/cm3 and it is flammable.Which test that she performed took advantage of this liquid's physical properties?
What is density?
number of atoms in [Cr(H2O)4Cl2]Cl 2(H2O)
What is 22?
1 Cr, 8 H, 4O, 9Cl
Cassidy filled a flask with 5 grams of water, and left it on a scale. A day later the scale read three grams. How could this be true?
What is an example of an exothermic chemical reaction that is happening in every cell of your body right now?
What is cellular respiration?
Trees build their bodies from cellulose (C6H10O5). Using what you know about photosynthesis and cellular respiration, describe where you think trees get this carbon from to make the cellulose?
All the atoms that trees use to build their bodies comes from photosynthesis.