One of the following is NOT a physical change: splitting wood, melting ice, burning wood or dissolving salt in water.
What is burning wood?
100
In the formula 5CaSO4, this is the number of oxygen atoms.
What is 20?
100
Every chemical reaction needs this to get started.
What is a certain amount of activation energy?
100
A reaction that releases energy is called this.
What is exothermic?
100
You can balance chemical equations by changing these.
What are coefficients?
200
This is the definition of chemistry.
What is the study of matter and how matter changes?
200
Chemical equations use these instead of words to summarize a reaction.
What are chemical formulas and other symbols?
200
The baking of bread may be described as being this type of chemical reaction.
What is endothermic because it is absorbing heat from its environment?
200
Baking soda and vinegar combined results in this type of chemical reaction.
What is endothermic?
200
This describes a synthesis reaction.
What is two elements combine to form a compound (more complex substance)?
300
This is the definition of matter.
What is anything that has mass and takes up space?
300
These are substances you have at the beginning of a chemical reaction and are listed on the left hand side of the arrow of a chemical equation.
What are reactants?
300
List 3 ways a chemist can control rates of chemical reactions.
What is by changing factors such as surface area, temperature, concentration, using a catalyst, or using an inhibitor?
300
During a chemical reaction chemical bonds can be formed when electrons are shared, gained or lost.....
What is all three?
300
These are the two types of changes that can occur in matter.
What are physical and chemical changes?
400
This is what occurs between atoms when a chemical change takes place.
What is bonds break and new bonds form?
400
The substances you have at the end of a chemical reaction.
What are products?
400
An increase in temperature will usually cause the rate of reaction to ________________.
What is increase?
400
The reaction 2HgO arrow 2Hg + O is an example of this type of reaction.
What is decomposition?
400
These may not be changed when balancing chemical equations.
What are subscripts?
500
Give three examples that a chemical change has taken place.
What is a change in energy (temperature change), color change, change of texture, formation of a precipitate, formation of a gas?
500
Explain why it is necessary to balance chemical equations.
What is because the principle of conservation of mass states that in a chemical reaction, the total mass of the reactants must equal the total mass of the products?
500
This is why our bodies have thousands of catalysts called enzymes.
What is because our normal body temperature is too low for many chemical reactions to take place without the help of catalysts?
500
Balance the reaction:
Na + H2O -> NaOH + H2
What is 2Na + 2H2O -> 2NaOH + H2
500
Balance the reaction:
HCl + Ca(OH)2 -> CaCl2 + H2O