Another science test
Which of the following occurs when chlorophyll breaks down into new substances?
A chemical reaction
How can you be sure a chemical reaction is happening?
A new substance with different properties forms.
What happens during a reaction?
Bonds are broken, atoms are rearranged, and new bonds are formed.
Leaves change color in the fall as a result of (blank) in the leaves.
Chemical changes
Which of the following causes leaves to change color?
Chlorophyll
What is a molecule made up of two atoms?
Diatomic
According to the law of conservation of energy, which of the following is not true?
Energy cannot change forms
Compare exothermic and endothermic reactions.
Exothermic releases energy, but endothermic takes in energy. They both allow heat to transfer.
Name the four signs of chemical reactions.
Gas is released, heat is transferred, color is changed, precipitate is formed.
What happens in an endothermic reaction?
He is taken in
When (blank) bump into one another without energy, chemical bonds can break.
Molecules
If the chemical properties of a substance have not changed, has a chemical reaction occurred?
No, because in order for a chemical reaction to occur, there has to be changes in the substance to produce a new one.
Steam escapes from a teapot. Is a chemical reaction occurring?
No, because liquid to gas would be a physical change, not a chemical change.
Which of the following is an example of an endothermic process?
Photosynthesis
When chemical bonds break, the atoms rearranged to form new (blank)
Substances
What happens to the atoms of the starting substances during a chemical reaction?
The atoms rearrange and new bonds form to make new substances.
Explain why the burning of charcoal in the grill is a chemical change.
The burning of charcoal in a grill is a chemical change because light, heat, and energy is given off from the fire to the charcoal then transferred to the food to allow it to cook.
Which of the following is true of the new materials formed in a chemical reaction?
Their physical and chemical properties differ from those of the original materials.
Which of the following is a sign of a chemical reaction?
Thermal energy from a fire
What are diatomic molecules?
Two atoms that are bonded together.
The force that holds two atoms together is called a(n)
chemical bond
What happens in an exothermic reaction?
heat is released